CN113266373B - Freezing wall and cement reinforcement combined enclosure structure in large-section tunnel construction and excavation method thereof - Google Patents
Freezing wall and cement reinforcement combined enclosure structure in large-section tunnel construction and excavation method thereof Download PDFInfo
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- 230000008014 freezing Effects 0.000 title claims abstract description 916
- 238000009412 basement excavation Methods 0.000 title claims abstract description 196
- 238000010276 construction Methods 0.000 title claims abstract description 167
- 230000002787 reinforcement Effects 0.000 title claims abstract description 138
- 238000000034 method Methods 0.000 title claims abstract description 109
- 239000004568 cement Substances 0.000 title claims abstract description 63
- 239000002689 soil Substances 0.000 claims abstract description 98
- 238000005553 drilling Methods 0.000 claims abstract description 37
- 239000011435 rock Substances 0.000 claims abstract description 22
- 238000013461 design Methods 0.000 claims abstract description 18
- 238000005728 strengthening Methods 0.000 claims description 116
- 238000005192 partition Methods 0.000 claims description 60
- 238000010438 heat treatment Methods 0.000 claims description 51
- 230000003014 reinforcing effect Effects 0.000 claims description 47
- 230000008569 process Effects 0.000 claims description 35
- 238000007789 sealing Methods 0.000 claims description 12
- 238000002844 melting Methods 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- 238000009529 body temperature measurement Methods 0.000 claims description 4
- 238000004078 waterproofing Methods 0.000 claims description 4
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/001—Improving soil or rock, e.g. by freezing; Injections
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/11—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means
- E02D3/115—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means by freezing
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/12—Consolidating by placing solidifying or pore-filling substances in the soil
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/20—Hydro energy
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Soil Sciences (AREA)
- Agronomy & Crop Science (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Excavating Of Shafts Or Tunnels (AREA)
Abstract
The invention discloses a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction and an excavation method thereof, wherein the enclosure structure comprises a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and a region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region; the cement reinforcement is positioned in surrounding rock along the excavation direction of the tunnel face of the large-section tunnel to be excavated. The excavation method comprises the following steps: drilling holes according to the planning and design of the cylindrical freezing wall, and installing a freezing system; after positive freezing is completed, grouting is carried out at a position 10m away from the excavated face. The invention is different from the traditional cup-shaped freezing mode, adopts a cylindrical freezing wall, does not need to drill a freezing hole on the face to be excavated, replaces the traditional end part full-hall freezing by horizontal grouting reinforcement, saves a great amount of drilling time and materials, and greatly reduces the excavation difficulty because the excavation area is a weak freezing area.
Description
Technical Field
The invention relates to the technical field of tunnel construction. In particular to a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction and an excavation method thereof.
Background
Compared with other small-section and short-distance tunnel engineering, the large-section and long-distance tunnel engineering has the advantages that the construction risk is more, the construction difficulty is higher, the structure, the construction environment and the construction organization of the tunnel are more complex, and a large number of engineering technical problems still exist. The method for constructing the concrete pile by the concrete pile is characterized in that a reasonable and optimal construction method is selected to safely pass through the engineering geology bad section, so that damage to the surrounding environment is reduced to the greatest extent, and the method is a very concerned problem of a main party, a design party, a construction party and a supervision party of engineering construction industry.
In order to build tunnels in unstable strata, a plurality of stratum pre-reinforcement technical measures are proposed at home and abroad, and grouting, small guide pipes, pipe sheds and other technologies are commonly applied in soil tunnels. The artificial freezing method is used as a temporary reinforcement technology and is widely applied to mine construction and municipal engineering, but the application experience in large-section long-distance tunnel engineering is still insufficient, and particularly, when a large-section long-distance tunnel needs to be built in an unstable stratum, a mature construction method is lacking. In the prior construction engineering, when the soil body at the periphery of the tunnel is reinforced by using a manual freezing method, a traditional cup-shaped freezing wall reinforcing mode is often adopted. The reinforcement mode needs to be frozen in a full hall, the number of holes is large, and a strong freezing area is formed in an excavation area, so that the excavation difficulty is increased, and the engineering quantity for pulling out the later frozen pipe is also large.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide the combined enclosure structure of the freezing wall and the cement reinforcement in the construction of the large-section tunnel and the excavation method thereof, so as to solve the problems of large drilling quantity, large excavation difficulty and the like when the peripheral soil body is reinforced by adopting the freezing method in the construction process of the large-section tunnel with larger stratum water inflow, large soil layer sand content and no open excavation condition.
In order to solve the technical problems, the invention provides the following technical scheme:
the combined enclosure structure of the freezing wall and the cement reinforcement in the construction of the large-section tunnel is characterized by comprising a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and a region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region; the cement reinforcement body is located in a non-excavation area of the tunnel face of the large-section tunnel to be excavated along the excavation direction.
The excavation method for the combined enclosure structure of the freezing wall and the cement reinforcement in the large-section tunnel construction comprises the following steps:
step A: drilling holes according to the design scheme of the cylindrical freezing wall, installing a freezing system, and actively freezing to form a frozen soil curtain, wherein the frozen soil curtain is the cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and the region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region;
And (B) step (B): after positive freezing is completed, performing primary horizontal grouting in surrounding rock 10m away from the face of the small section to be excavated to form the cement reinforcing body;
step C: after the excavation acceptance check is passed, carrying out sectional horizontal excavation until the primary support of the excavated part is completed, and carrying out next-stage grouting and excavation; sequentially excavating after finishing horizontal grouting every 10m until the primary support of the section to be excavated is completed; grouting reinforcement is carried out after the end is excavated, so that the end reinforcement is completed;
step D: and (3) performing secondary lining construction after water proofing is finished, stopping freezing, plugging all freezing holes inside and outside, and filling, melting, sinking and grouting.
In the above-mentioned excavation method that adopts the freezing wall and cement reinforcement to unite the envelope in the tunnel construction of a large section, in step B, according to the rule of laying the freezing hole, divide the construction area of the large section to be excavated into 4 excavation areas of first step, second step, third step and fourth step sequentially from top to bottom, each excavation area is horizontal excavation; positive freezing is classified into first-stage freezing and second-stage freezing; the first-stage freezing comprises freezing the two excavation areas of the first step and the second step; the second-stage freezing comprises freezing the two excavation areas of the third step and the fourth step; and the second-stage freezing is performed after the second step excavation area is excavated; step C can be divided into the following steps:
Digging a first step in the step (C-11): sequentially carrying out sectional horizontal excavation after horizontal grouting for every 10m, and supporting along with excavation until the primary support of the first step is completed; then carrying out horizontal grouting reinforcement after the first step is excavated to the end head so as to finish the end reinforcement of the first step; after the first step excavation is completed completely: installing a first middle partition plate in the construction of a first step, and performing grouting end-capping reinforcement on a to-be-excavated area of a second step by utilizing a vertical grouting hole in the construction of an excavated space of the first step;
and (3) excavating a second step in the step (C-12): excavating a second step by adopting an excavating method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the second step; after the excavation of the second step is completed, constructing and installing a first bottom middle partition plate on the second step, and performing grouting end-capping reinforcement on a third step to-be-excavated area by utilizing a vertical grouting hole constructed in an excavation space of the second step;
and (3) excavating a third step: after the second step is excavated, performing second-stage freezing, and after the second-stage freezing is finished, excavating the third step according to the excavation construction method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the third step; after the excavation of the third step is completed, constructing and installing a second middle partition plate on the third step, and performing grouting end-capping reinforcement on a fourth step to-be-excavated area by utilizing a vertical grouting hole in the excavation space of the third step;
Excavating a fourth step in the step (C-14): excavating a fourth step by adopting the excavating method of the first step; and (3) carrying out horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the fourth step.
In the above-mentioned excavation method that adopts the freezing wall and cement reinforcement to unite the envelope in the tunnel construction of a large section, in step B, according to the rule of laying the freezing hole, divide the construction area of the large section to be excavated into 3 excavation areas of first step, second step and third step sequentially from top to bottom, each excavation area is horizontal excavation; step C can be divided into the following steps:
digging a first step in the step (C-21): sequentially carrying out sectional horizontal excavation after horizontal grouting for every 10m, and supporting along with excavation until the primary support of the first step is completed; then carrying out horizontal grouting reinforcement after the first step is excavated to the end head so as to finish the end reinforcement of the first step; after the first step excavation is completed completely: installing a third middle partition plate A in the construction of the first step, and performing grouting end-capping reinforcement on a to-be-excavated area of the second step by utilizing a vertical grouting hole in the construction of an excavated space of the first step;
and (3) excavating a second step in the step (C-22): excavating a second step by adopting an excavating method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the second step; after the excavation of the second step is completed, a third middle partition board B is installed on the second step in a construction mode, and grouting end-sealing reinforcement is carried out on a third step area to be excavated by utilizing a vertical grouting hole in the construction mode of an excavation space of the second step;
And (3) excavating a third step in the step (C-23): excavating a third step by adopting the excavating method of the first step; and (3) carrying out horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the third step.
The technical scheme of the invention has the following beneficial technical effects:
(1) According to the invention, the soil body at the periphery of the planned tunnel is frozen and reinforced in a cylindrical freezing wall mode, so that a frozen soil curtain with high strength and good sealing property can be formed, and a weak freezing area is formed in an excavation area, so that the excavation difficulty of the excavation area is reduced; then, horizontal advanced grouting reinforcement is carried out on the tunnel face to form a freezing wall and cement reinforcement combined enclosure structure, and the enclosure structure can meet the construction requirements of the large-section tunnel in the unstable stratum.
(2) According to the invention, as the section of the large-section tunnel is larger and the stratum structure is unstable, the frozen soil curtain is divided into two freezing reinforcement areas, so that the strength of soil around the section and the strength of the enclosure structure in the excavation process can be ensured, and the construction safety risk caused by insufficient reinforcement strength is avoided; in addition, the invention adopts a cylindrical freezing wall mode for reinforcement, and does not need to increase freezing holes on the face, but adopts horizontal grouting to replace the freezing holes, thereby saving a great amount of drilling time and materials and improving the construction efficiency. Before excavation, horizontal advanced grouting reinforcement is carried out on the tunnel face of the large-section tunnel, and a complete enclosure structure can be formed in an area to be excavated, so that stability and water-proof performance of surrounding rock in construction are ensured, and smooth construction is ensured. In the excavation process, the whole construction process is monitored in real time, the stratum deformation condition is observed in time, and the whole construction process can be ensured to be carried out smoothly.
(3) The excavation construction method is different from the traditional cup-shaped freezing mode, adopts a cylindrical freezing wall, does not need to drill a freezing hole on a tunnel face, replaces the traditional full end freezing by horizontal grouting reinforcement, saves a large amount of drilling time and materials, ensures that an excavation area is a weak freezing area, and reduces the excavation difficulty. The construction area of a large section to be excavated is divided into 3 or 4 excavation areas, the excavation areas are sequentially and horizontally excavated from top to bottom, in addition, in each layer of excavation construction, a partition board is used for grouting, end-sealing and reinforcing of the next step in the construction process by utilizing the excavation space of the previous step, and the problems that water and sand burst possibly occur due to unreinforced bottom of a pit shaft type freezing wall during excavation of the next step can be avoided; the construction method is characterized in that the construction method is closed into a ring in time along with the excavation and the supporting in the excavation process, so that the blank period is shortened, and the construction problem cannot be caused by unstable stratum in the construction process.
Drawings
FIG. 1 is a schematic view of the structure of a cross channel # 1 in embodiment 2 of the present invention;
FIG. 2 is a cross-sectional view of the 1# cross-sectional channel A-A in example 2 of the present invention;
FIG. 3 is a cross-sectional view of the 1# cross-channel B-B in example 2 of the present invention;
FIG. 4a is a longitudinal cross-sectional view of a frozen wall at the first stage of the cross-channel # 1 in example 2 of the present invention;
FIG. 4b is a cross-sectional view of the first stage freeze wall 1-1 of the cross-channel 1# in example 2 of the present invention;
FIG. 4c is a cross-sectional view of the first stage freeze wall 2-2 of the cross-channel # 1 in example 2 of the present invention;
FIG. 5a is a longitudinal cross-sectional view of the frozen wall of the second stage of the cross-channel # 1 in example 2 of the present invention;
FIG. 5b is a cross-sectional view of the second stage freeze wall 1-1 of cross-channel 1# in example 2 of the present invention;
FIG. 5c is a cross-sectional view of the second stage freeze wall 2-2 of the cross-channel # 1 in example 2 of the present invention;
FIG. 6a is a view showing the arrangement of freezing holes in the outer ring of the 1# cross channel in embodiment 2 of the present invention;
FIG. 6b is a view showing the arrangement of the inner ring and bottom freezing holes of the # 1 transverse channel in example 2 of the present invention;
FIG. 7 is a diagram showing the position of the freezing hole opening of the No. 1 cross-channel in example 2 of the present invention;
FIG. 8 is a schematic diagram of a step 1 of excavating a 1# cross channel in the embodiment 2 of the present invention;
FIG. 9 is a schematic diagram of a step 2 of excavating a 1# cross channel in the embodiment 2 of the present invention;
FIG. 10 is a schematic diagram of a step 3 of excavating a 1# cross channel in the embodiment 2 of the present invention;
FIG. 11 is a schematic diagram of a step 4 of excavating a 1# cross channel in the embodiment 2 of the present invention;
FIG. 12 is a schematic diagram of a step 5 of excavating a 1# cross channel in embodiment 2 of the present invention;
FIG. 13 is a schematic diagram of a step 6 of excavating a 1# cross channel in embodiment 2 of the present invention;
FIG. 14 is a schematic diagram of a step 7 of excavating a 1# cross channel in the embodiment 2 of the present invention;
FIG. 15 is a schematic diagram showing the completion of drilling of the 1# cross-channel in example 2 of the present invention;
FIG. 16 is a positive freeze pattern of the cross channel # 1 in example 2 of the present invention;
FIG. 17 is a schematic diagram of the first step excavation of the No. 1 cross-channel in embodiment 2 of the present invention;
FIG. 18 is a schematic diagram showing the completion of excavation of the 1# cross channel in embodiment 2 of the present invention;
FIG. 19 is a longitudinal sectional view of a first stage freezing and reinforcing area of a combined enclosure of a freezing wall and a cement reinforcement in construction of a large-section tunnel in accordance with embodiment 1 of the present invention;
FIG. 20 is a longitudinal sectional view of a second stage freezing and reinforcing area of a combined enclosure of a freezing wall and a cement reinforcement in construction of a large-section tunnel in embodiment 1 of the present invention;
FIG. 21 is a cross-sectional view of a first stage freezing and reinforcing area of a combined retaining structure of a freezing wall and a cement reinforcement in the construction of a large-section tunnel in embodiment 1 of the present invention;
FIG. 22 is a cross-sectional view of a second stage freezing and reinforcing area of a combined retaining structure of a freezing wall and a cement reinforcement in the construction of a large-section tunnel in embodiment 1 of the present invention;
FIG. 23 is a schematic view showing the structure of the 2# cross channel in embodiment 4 of the present invention;
FIG. 24 is a schematic view showing the longitudinal sectional structure of the frozen wall of the 2# transverse passage in embodiment 4 of the present invention;
FIG. 25a is a schematic cross-sectional view of the frozen wall 1-1 of the 2# cross-channel in embodiment 4 of the present invention;
FIG. 25b is a schematic cross-sectional view of the freezing wall 2-2 of the 2# cross-channel in embodiment 4 of the present invention;
FIG. 26a is a view showing the arrangement of freezing holes in the outer ring of the 2# cross channel in example 4 of the present invention;
FIG. 26b is a view showing the arrangement of the inner ring and bottom freezing holes of the 2# cross channel in example 4 of the present invention;
FIG. 27 is a view showing the position of the freezing hole opening of the 2# cross channel in example 4 of the present invention;
FIG. 28 is a schematic diagram of a step 1 of excavating a 2# cross channel in embodiment 4 of the present invention;
FIG. 29 is a schematic diagram of a step 2 of excavating a 2# cross channel in embodiment 4 of the present invention;
FIG. 30 is a schematic diagram of a step 3 of excavating a 2# cross channel in embodiment 4 of the present invention;
FIG. 31 is a schematic diagram of a step 4 of excavating a 2# cross channel in the embodiment 4 of the present invention;
FIG. 32 is a schematic diagram of a step 5 of excavating a 2# cross channel in embodiment 4 of the present invention;
FIG. 33 is a schematic diagram of a step 6 of excavating a 2# cross channel in embodiment 4 of the present invention;
FIG. 34 is a schematic diagram showing the completion of drilling of the 2# cross channel in example 4 of the present invention;
FIG. 35 is a positive freeze pattern of the 2# transverse channel in example 4 of the present invention;
FIG. 36 is a schematic view showing the completion of excavation of the 2# cross channel in embodiment 4 of the present invention;
FIG. 37 is a schematic view showing the structure of a third freeze-hardened region of a 2# cross channel in embodiment 3 of the present invention;
FIG. 38 is a schematic diagram showing the arrangement of the grouting holes for the 1# horizontal channel in example 2 of the present invention.
The reference numerals in the drawings are as follows: 1-freezing the reinforced area in the first period; 11-a first upper freeze wall; 12-first bottom intermediate shelf freezing wall; 13-first side wall freeze wall; 14-a first intermediate wall freeze wall; 2-freezing the reinforced area in the second period; 21-a second upper freeze wall; 22-a second bottom freeze wall; 23-a second side wall freezing wall; 24-second intermediate partition freezing wall; 3-a tunnel face of a large-section tunnel to be excavated; 30-a third freeze-hardened zone; 301-a third upper freeze wall; 302-a third bottom freeze wall; 303-a third side wall freezing wall; 304-third intermediate partition freezing wall a; 305-third intermediate partition freezing wall B; 4-a cement grouting area; 5-a small-section tunnel face to be excavated; 6-a pressure relief hole group X; 61-a first pressure relief aperture group X; 62-a second pressure relief aperture group X; 63-a third pressure relief port group X; 64-a fourth pressure relief port group X; 7-heating the hole group DJ; 81-an outer ring freezing hole group D; 82-a first column of outer ring freezing hole groups FB; 83-second column outer ring freezing hole group D; 84-first row outer ring freezing hole group DB; 85-second row outer ring freezing hole group DB; 86-third row outer ring freezing hole group DB; 87-fourth row outer ring freezing hole group DB; 88-the freezing hole group DB of the outer ring of the fifth row; 89-sixth row outer ring freezing hole group DB; 91-outer ring auxiliary freezing hole group DN; 92-a first column outer ring auxiliary freezing hole group DN; 101-first interface enhancing frozen well group G; 102-second interface enhancing frozen pore group G; 103-third interface enhancing frozen pore group G; 104-fourth interface strengthening freeze hole group G; 105-fifth interface enhances the frozen well group G.
Detailed Description
Example 1
As shown in fig. 19 and 20, a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction comprises a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and the region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region; the frozen soil curtain comprises a first-period freezing and reinforcing area 1 and a second-period freezing and reinforcing area 2; the cement reinforcement body is positioned in a non-excavation area of the tunnel face 3 of the large-section tunnel to be excavated along the excavation direction. According to the method, the soil body at the periphery of the planned tunnel is frozen and reinforced in a cylindrical freezing wall mode, a frozen soil curtain with high strength and good sealing performance can be formed, a weak freezing area is formed in an excavation area, and the excavation difficulty of the excavation area is reduced; and then carrying out horizontal advanced grouting reinforcement on the tunnel face to form a freezing wall and cement reinforcement combined enclosure structure, wherein the enclosure structure can meet the construction requirement of the large-section tunnel in the unstable stratum.
As shown in fig. 21, the first-stage freezing and reinforcing area 1 is a straight wall arc top-bottom type freezing wall in a Chinese character 'ri'; the first-stage freezing and reinforcing zone 1 comprises a first upper freezing wall 11, a first bottom middle partition freezing wall 12, a first side wall freezing wall 13 and a first middle partition freezing wall 14; the thickness of the first upper freezing wall 11 is 3.0m, the thickness of the first bottom middle partition freezing wall 12 is 3.5m, and the thicknesses of the first side wall freezing wall 13 and the first middle partition freezing wall 14 are 2.5m; the first upper freezing wall 11, the first bottom middle partition freezing wall 12, the first side wall freezing wall 13 and the first middle partition freezing wall 14 all extend 8.0m towards the trenchless area along the front face 3;
As shown in fig. 22, the second-stage freezing and reinforcing area 2 is a straight wall arc bottom type freezing wall in a shape of Chinese character 'ri'; the second stage freezing and reinforcing zone 2 comprises a second upper freezing wall 21, a second bottom freezing wall 22, a second side freezing wall 23 and a second middle partition freezing wall 24; the second upper freezing wall 21 is connected with the first bottom middle partition freezing wall 12 of the first period freezing and reinforcing zone 1; the thickness of the second side wall freezing wall 23 and the second middle partition freezing wall 24 is 2.5m, the thickness of the second bottom freezing wall 22 is 3.5m, and the second upper freezing wall 21, the second bottom freezing wall 22, the second side wall freezing wall 23 and the second middle partition freezing wall 24 extend to the trenchless area along the front tunnel face 3 by 8.0m. Because the section of the large-section tunnel is larger and the stratum structure is unstable, the frozen soil curtain is divided into two freezing reinforcement areas, so that the strength of soil around the section and the strength of the enclosure structure in the process of excavation construction can be ensured, and the construction safety risk caused by insufficient reinforcement strength is avoided; in addition, the embodiment adopts a cylindrical freezing wall mode for reinforcement, and the freezing holes are not required to be added on the face, but are replaced by horizontal grouting, so that a great amount of drilling time and materials are saved, and the construction efficiency is improved.
The cement grouting body is a cement grouting area 4, the tunnel face 3 of the large-section tunnel to be excavated consists of four small-section tunnel faces 5 to be excavated which are sequentially arranged from top to bottom, and the cement grouting area 4 is positioned in front of the small-section tunnel faces 5 to be excavated; and the cement grouting area 4 is arranged at intervals of 10m along the excavation direction of the face 5 with the small section to be excavated in the excavation process. Before excavation, horizontal advanced grouting reinforcement is carried out on the tunnel face of the large-section tunnel, and a complete enclosure structure can be formed in an area to be excavated, so that the stability of stratum in construction is ensured, and smooth construction is ensured.
As shown in fig. 7, the freezing holes of the frozen soil curtain are arranged on the longitudinal section of the area to be excavated as follows:
above the area to be excavated: the outer ring auxiliary freezing hole group DN91 is formed by an outer ring freezing hole group D81 formed by 19 outer ring freezing holes and an outer ring auxiliary freezing hole group DN91 formed by 10 outer ring auxiliary freezing holes, wherein the outer ring freezing hole group D81 formed by 7 pressure relief holes, the heating hole group DJ7 formed by 9 heating holes and the outer ring auxiliary freezing hole group D81 formed by 10 outer ring auxiliary freezing holes are sequentially distributed from top to bottom; the pressure relief holes in the pressure relief hole group X6 are distributed at equal intervals along the horizontal direction, the hole spacing between two adjacent pressure relief holes is 1500mm, and the vertical distance L1 between the pressure relief holes and the arc top of the area to be excavated is 6800mm; the heating holes in the heating hole group DJ7 are distributed at equal intervals along the same heating hole group circular arc, the hole interval between two adjacent heating holes is 1500mm, the arc top of the heating hole group circular arc and the arc top of the area to be excavated are on the same vertical line, the distance between the two is 5460mm, and the longitudinal distance L2 from any point on the heating hole group circular arc to the circular arc where the upper edge of the area to be excavated is located is equal; the 15 outer ring freezing holes in the outer ring freezing hole group D81 are distributed along the same outer ring freezing hole group circular arc, the hole spacing between every two adjacent outer ring freezing holes is 800mm, 1 outer ring freezing hole is distributed on the arc top of the outer ring freezing hole group circular arc, 6 outer ring freezing holes with equal spacing are respectively distributed from the arc top to two sides of the outer ring freezing hole group circular arc, one outer ring freezing hole is respectively arranged at the end point of the outer ring freezing hole group circular arc, and two outer ring freezing holes respectively positioned at two sides of the outer ring freezing hole group circular arc are distributed on the horizontal line between the last outer ring freezing hole and the last outer ring freezing hole at the end of the outer ring freezing hole group circular arc; the arc top of the arc of the outer ring freezing hole group and the arc top of the area to be excavated are on the same vertical line, the distance between the arc top of the arc of the outer ring freezing hole group and the arc top of the area to be excavated is 4660mm, and the longitudinal distance L3 from any point on the arc of the outer ring freezing hole group to the arc where the upper edge of the area to be excavated is located is equal; the 8 outer ring auxiliary freezing holes in the outer ring auxiliary freezing hole group DN91 are distributed on the same outer ring auxiliary freezing hole group circular arc at equal intervals, and the hole spacing between every two adjacent outer ring auxiliary freezing holes is 1200mm; in addition, 2 outer ring auxiliary freezing holes are respectively distributed near the tail end of the outer ring auxiliary freezing hole group arc and are positioned between the outer ring auxiliary freezing hole group arc and the outer ring freezing hole group arc, the arc tops of the outer ring auxiliary freezing hole group arc and the arc tops of the area to be excavated are on the same vertical line, the distance between the two is 3160mm, and the longitudinal distance L4 from any point on the outer ring auxiliary freezing hole group arc to the arc where the edge on the area to be excavated is equal;
A first temperature measuring hole, a second temperature measuring hole and a third temperature measuring hole are also distributed above the area to be excavated, the first temperature measuring hole is distributed on the circular arc of the heating hole group and is positioned at the left side of the arc top of the circular arc of the heating hole group, and the second temperature measuring hole and the first temperature measuring hole are on the same horizontal line and are positioned between the circular arc of the heating hole group and the circular arc of the outer ring freezing hole group; the third temperature measuring hole is positioned right below the arc top of the outer ring auxiliary freezing hole group;
left side of the area to be excavated: a first row of outer ring freezing hole groups FB82 and a second row of outer ring freezing hole groups D83 are longitudinally distributed, and the distance between the first row of outer ring freezing hole groups FB82 and the area to be excavated is larger than the distance between the second row of outer ring freezing hole groups D83 and the area to be excavated; the longitudinal straight line where the first column outer ring freezing hole group FB82 is located is also provided with auxiliary freezing holes and temperature measuring holes, the longitudinal straight line where the second column outer ring freezing hole group D83 is located is also provided with auxiliary freezing holes, and the auxiliary freezing holes and the temperature measuring holes are distributed in the area between the second column outer ring freezing hole group D83 and the area to be excavated;
hole groups symmetrical to the left side of the area to be excavated about the longitudinal center line of the area to be excavated are distributed on the right side of the area to be excavated;
in the area to be excavated: the first pressure relief hole group X61 composed of 2 pressure relief holes, the first interface strengthening freezing hole group G101 composed of 7 interface strengthening freezing holes, the second interface strengthening freezing hole group G102 composed of 4 interface strengthening freezing holes, the second pressure relief hole group X62 composed of 2 pressure relief holes, the third interface strengthening freezing hole group G103 composed of 7 interface strengthening freezing holes, the fourth interface strengthening freezing hole group G104 composed of 8 interface strengthening freezing holes, the third pressure relief hole group X63 composed of 2 pressure relief holes, the fifth interface strengthening freezing hole group G105 composed of 7 interface strengthening freezing holes and the fourth pressure relief hole group X64 composed of 2 pressure relief holes are distributed in sequence from top to bottom; the 2 pressure relief holes in the first pressure relief hole group X61 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L5 between the pressure relief holes and the arc top of the area to be excavated is 782mm, and the hole spacing between the 2 pressure relief holes is 3000mm; 7 interface strengthening freezing holes in the first interface strengthening freezing hole group G101 are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L51 between the straight line formed by connecting the first interface strengthening freezing hole groups G101 and the arc top of the area to be excavated is 5300mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm; the 4 interface strengthening freezing holes in the second interface strengthening freezing hole group G102 are formed in the way of equally spacing along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated; the vertical distance L6 between the straight line formed by connecting the second interface strengthening freezing hole group G102 and the arc top of the area to be excavated is 6103mm, and the hole spacing between two adjacent interface strengthening freezing holes is 2000mm; the 2 pressure relief holes in the second pressure relief hole group X62 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L7 between the pressure relief holes and the arc top of the area to be excavated is 7384mm; the hole spacing between the 2 pressure relief holes is 3000mm; 7 interface strengthening freezing holes in the third interface strengthening freezing hole group G103 are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L8 between the straight line formed by connecting the third interface strengthening freezing hole group G103 and the arc top of the area to be excavated is 10303mm, and the hole spacing between every two adjacent interface strengthening freezing holes is 1230mm; the 8 interface strengthening freezing holes in the fourth interface strengthening freezing hole group G104 are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated; the vertical distance L9 between the straight line formed by connecting the second interface strengthening freezing hole group G104 and the arc top of the area to be excavated is 11000mm, and the hole spacing between every two adjacent interface strengthening freezing holes is 1200mm; the 2 pressure relief holes in the third pressure relief hole group X63 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L10 between the pressure relief holes and the arc top of the area to be excavated is 11172mm; the hole spacing between the 2 pressure relief holes is 3000mm; 7 interface strengthening freezing holes in the fifth interface strengthening freezing hole group G105 are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L11 between the straight line formed by connecting the third interface strengthening freezing hole group G105 and the arc top of the area to be excavated is 11853mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm; the 2 pressure relief holes in the fourth pressure relief hole group X64 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L12 between the pressure relief holes and the arc top of the area to be excavated is 12262mm; the hole spacing between the 2 pressure relief holes is 3000mm;
A fourth temperature measuring hole, a fifth temperature measuring hole, a sixth temperature measuring hole and a seventh temperature measuring hole are also formed in the region to be excavated, 4 temperature measuring holes are formed in the longitudinal central axis of the region to be excavated, and the fourth temperature measuring hole is positioned between the first interface reinforced freezing hole group G101 and the second interface reinforced freezing hole group G102; the fifth temperature measuring hole is positioned on a straight line formed by connecting the second interface reinforced freezing hole group G104; the sixth temperature measuring hole is positioned between the third pressure relief hole group X63 and the fifth interface strengthening freezing hole group G105; the seventh temperature measuring hole is positioned below the fourth pressure relief hole group X64;
a first row of outer ring auxiliary freezing hole groups DN92 consisting of 4 outer ring auxiliary freezing holes are longitudinally distributed at the edges of two sides of the region to be excavated;
below the area to be excavated: a first row of outer ring freezing hole groups DB84 formed by 11 outer ring freezing holes, a second row of outer ring freezing hole groups DB85 formed by 10 outer ring freezing holes, a third row of outer ring freezing hole groups DB86 formed by 11 outer ring freezing holes, a fourth row of outer ring freezing hole groups DB87 formed by 10 outer ring freezing holes and a fifth row of outer ring freezing hole groups DB88 formed by 11 outer ring freezing holes are sequentially distributed from top to bottom; 11 outer ring freezing holes in the first row of outer ring freezing hole groups DB84 are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L13 between a straight line formed by connecting the first row of outer ring freezing hole groups DB84 and the arc bottom of the region to be excavated is 13133mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm; 10 outer ring freezing holes in the second row of outer ring freezing hole groups DB85 are distributed at equal intervals along the horizontal direction; the vertical distance L14 between a straight line formed by connecting the second row of outer ring freezing hole groups DB85 and the arc bottom of the region to be excavated is 13463mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm; 11 outer ring freezing holes in the third row of outer ring freezing hole groups DB86 are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L15 between a straight line formed by connecting the third row of outer ring freezing hole groups DB86 and the arc bottom of the region to be excavated is 13760mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm; 10 outer ring freezing holes in the fourth row outer ring freezing hole group DB87 are distributed at equal intervals along the horizontal direction; the vertical distance L16 between a straight line formed by connecting the freezing hole groups DB87 of the fourth row of outer rings and the arc bottom of the region to be excavated is 14163mm, and the hole spacing between every two adjacent freezing holes of the outer rings is 1200mm; 11 outer ring freezing holes in the fifth row outer ring freezing hole group DB88 are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L17 between the straight line formed by connecting the freezing hole groups DB88 of the outer ring of the fifth row and the arc bottom of the region to be excavated is 14463mm, and the hole spacing between every two adjacent freezing holes of the outer ring is 1200mm.
Example 2
The excavation construction test was performed by using the excavation construction method of the combined enclosure structure of the freezing wall and the cement reinforcement in the large-section tunnel construction of embodiment 1, taking the 1# cross-channel freezing engineering of the large-section tunnel between the XXX station of the XXX subway XXX line and the XXX station as an example.
1 engineering overview
1.1 engineering content
The construction of the large-section tunnel between the XXX station and the XXX station of the XXX subway XXX number line is to adopt a construction method which takes a shield method as a main method and a mine method as an auxiliary method. The XXX section adopts a three-line shield, the local transition line section adopts a hidden excavation method for construction, the hidden excavation part mainly comprises a # 1 transverse channel, a # 2 transverse channel, a wiring extension section, a transition line section and a station hidden excavation section, the total length is about 265m, and the maximum excavation section width is 17.6m. After the section leaves the XXX station, the section is worn under the XXX golf course, and most of the section is positioned below the golf course and laid along the south side of the XXX road.
The construction of the No. 1 working well is completed, and the construction method of reinforcing by a freezing method and underground excavation by a mining method is adopted in the No. 1 transverse channel in the XXX section because the No. 1 working well is larger in stratum water inflow, large in soil sand content and self-stabilizing and poor in soil layer and does not have open excavation conditions.
1.2 engineering geology and hydrogeology
1.2.1 topography and topography
XXX is located in the middle of the strongback (tertiary unit) in Guangdong, and wide-range, thin dog-bone and wide-range three-fracture are basic frameworks of the structure of the region, and are mainly divided into four structural regions by taking wide-range fracture and thin dog-bone fracture as boundaries: the urban increasing protrusion, the flower depression, the Dongguan basin and the three water breaking basin. The line in the zone is located in the Dongguan basin.
The interval is positioned in XXX region of XXX city, and the landform unit is a unit for transition from alluvial plain zone to small basin zone of pre-mountain alluvial zone, inter-mountain alluvial zone, denudation hills and micro-hills land landform.
1.2.2 engineering geology
The No. 1 transverse channel mainly penetrates through a plastic sandy cohesive soil layer <5Z-1>, a hard plastic sandy cohesive soil layer <5Z-2> and a fully weathered mixed granite <6Z >; the 2# transverse channel mainly penetrates through a hard plastic sandy cohesive soil layer <5Z-2>, and sandy cohesive soil <7Z-B >; the thickness of the top soil of the transverse channel is 7m.
The geological condition of the interval is complex, and the lower bedrock is mainly various rocks such as clastic rock, carbonaceous shale, carbonaceous limestone, mixed granite and the like. In this embodiment, the mixed granite residual soil can be divided into plastic sandy cohesive soil (5Z-1) and hard plastic sandy cohesive soil (5Z-2).
The # 1 transverse channel traverses bad geological zones mainly comprises: residual earth formations, sand liquefaction, and the like.
(1) Ground subsidence: filling soil (1) and mucky soil (4-2 b) are distributed on the ground surface in the field, and if frost heaving of a transverse channel is excessive, turf cracking damage in the foot lake golf course can be caused.
(2) Ground collapse: the bottom of the No. 1 transverse channel penetrates through the mixed granite residual soil stratum, the stratum is mainly hard plastic sandy cohesive soil, the full weathering is hard soil, the stratum is easy to disintegrate when meeting water, engineering water properties are poor, surrounding rock stability is poor, and collapse accidents can be induced if a freezing wall and a supporting structure are improper and the combined system is seriously deformed.
(3) Disturbance of the formation: the No. 1 transverse channel is mainly artificial filled soil, sandy clay, residual soil, full and strong weathered mixed granite, and has poor overall mechanical properties, and is easy to soften and disintegrate when meeting water.
1.2.3 hydrogeology
The underground water level disclosed by the survey of the range of the 1# transverse channel is shallower, the water level burial depth is 1.80-18.10 m, the change of the underground water level is closely related to occurrence, supply and drainage of the underground water level and is influenced by seasonal change, the water level is obviously increased in the supply period of the underground water within 4-9 months each year, the underground water consumption period and the drainage period are within 10-3 months each year, the underground water level is reduced along with the underground water level, and the annual change range is 2.5-3.0 m. The underground water is divided into fourth-series soil layer pore water, lamellar bedrock fracture water, blocky bedrock fracture water and carbonate rock fracture karst cave water according to the occurrence mode. Because the topography of the local site has larger fluctuation and deeper topography cutting, the groundwater mainly circulates vertically, the runoff path of the groundwater is shorter, the runoff direction is generally consistent with the slope direction, the groundwater is mostly excreted to nearby valleys in a scattered flow mode, and in addition, the groundwater is excreted in the modes of surface evaporation, vegetation leaf surface transpiration and the like.
1.3 1# transverse channel structure
The size of the No. 1 working well is 12m multiplied by 9.5m (length multiplied by width), the tunnel bottom elevation is 7.790m, and the ground elevation is 34.000m. The maintenance structure of the No. 1 working well is an underground diaphragm wall with the thickness of 800mm, and 4 ring frame beams with the thickness of 1.8mx1.5m (width x height) are arranged inside the underground diaphragm wall. The length of the 1# transverse channel is 31.00m, the cross section of the 1# transverse channel is a variable cross section, the cross section of the inlet channel B-B is 9.1m wide and 13.00m high, and the cross section of the channel end D-D is 9.1m wide and 18.25m high. The structure of the 1# transverse channel is shown in figures 1 to 3.
The No. 1 transverse channel is excavated to divide four steps, and the middle partition plate is I25a section steel and C25 sprayed concrete with the thickness of 320 mm. The primary support of the No. 1 transverse channel is C25P6 shotcrete with the thickness of 350mm and a grid steel frame, and the secondary lining structure is C35P6 impervious concrete with the thickness of 700 mm.
2 freezing design scheme
Freezing wall and cement reinforcement combined enclosure structure
For a large-section tunnel with larger stratum water inflow and large soil layer sand content and without open excavation conditions, a combined retaining structure of freezing walls and cement reinforcement and a mining method excavation construction method can be adopted.
The overall construction scheme is as follows: the method comprises the steps of adopting a cylindrical freezing wall form to freeze and consolidate soil bodies on the periphery of a planned tunnel, forming a frozen soil curtain with high strength and good sealing performance, forming a weak freezing area in an excavated area, then carrying out horizontal advanced grouting reinforcement on a tunnel face to form a combined enclosure structure of the freezing wall and a cement reinforcement body, and carrying out tunnel excavation supporting construction by adopting a mine method after the quality of the enclosure structure is detected to be qualified.
The combined enclosure structure has the advantages that: the traditional freezing wall is a cup-shaped freezing wall, the cup-shaped freezing wall is required to be frozen by adopting a full chamber, the number of holes to be drilled is large, a strong freezing area is formed in an excavation area, the excavation difficulty is high, and the end freezing holes are removed from the combined enclosure structure of the freezing wall and the cement reinforcing body, namely, the traditional end freezing is replaced by horizontal grouting reinforcement, so that a large amount of drilling time and materials are saved, the excavation area is a weak freezing area, and the excavation difficulty is reduced.
The freezing method for reinforcing the stratum has the outstanding advantages that: the frozen soil curtain has good uniformity, tight combination with the maintenance structure wall, good reinforcement effect and safe and reliable construction. The general scheme of the freezing construction of the No. 1 transverse channel is as follows: by adopting a freezing and reinforcing scheme, the soil body in the range of the peripheral freezing wall of the planned transverse channel is frozen and reinforced in the form of an outer ring cylindrical freezing wall, a frozen soil curtain with high strength is formed, and a weak freezing area is formed in an excavated area. In order to control formation deformation caused by freeze thawing of soil layers, tracking grouting is needed in the thawing process of a freezing and reinforcing area. The monitoring of deformation and freezing system parameters is enhanced in the whole construction process.
2.1 frozen design drawing
According to the design, the No. 1 transverse channel is frozen in two stages, the straight wall arc top and bottom type freezing wall is adopted in the first stage freezing, the thickness of the upper freezing wall is 3.0m, the thickness of the side wall and the middle partition plate freezing wall is 2.5m, the average thickness of the bottom middle partition plate freezing wall is 3.5m, and the freezing wall at the front end excavation face extends by 8.0m. The first stage freezing walls of the 1# transverse channel are shown in fig. 4a, 4b and 4c.
According to the design, the second-stage freezing of the No. 1 transverse channel adopts a straight wall arc bottom type freezing wall, the upper part of the straight wall arc bottom type freezing wall is connected with the bottom freezing wall frozen in the first stage, the thickness of the side wall freezing wall is 2.5m, the average thickness of the bottom plate freezing wall is 3.5m, and the freezing wall at the front end excavation face extends by 8.0m. The second-stage freezing and freezing walls of the No. 1 transverse channel are shown in fig. 5a, 5b and 5c.
The construction freezing holes are divided into outer ring freezing holes D, DB and FB, outer ring auxiliary freezing holes DN, DNB and F, and interface reinforcing freezing holes G; temperature measurement hole C, release hole X, heating hole DJ. The arrangement of the freezing holes of the 1# transverse channel is shown in fig. 6a and 6b, and the opening positions are shown in fig. 7.
2.2 freezing design parameters
The main parameters of the freezing design are shown in table 1:
TABLE 1
2.3 construction emphasis and difficulty
(1) Engineering geological risk
The No. 1 transverse channel is mainly positioned in a mixed granite residual soil stratum, is difficult to construct in engineering of the embodiment, is broken in rock, is easy to soften when meeting water, belongs to V-class surrounding rock, and has poor geological conditions. The upper part of the No. 1 transverse channel is positioned in a plastic sandy cohesive soil layer <5Z-1> and a hard plastic sandy cohesive soil layer <5Z-2>, the soil layer is disintegrated by water, the sand content is large, and the phenomena of sand burst, mud burst and the like easily occur in drilling holes; the bottom is positioned at the strong weathered mixed granite <6Z >, the drilling construction of partial frozen holes needs to pass through soft and hard stratum, and the drilling construction difficulty is high.
(2) Difficulty in drilling construction
The number of the freezing holes of the No. 1 transverse channel is up to 266 (including 225 freezing holes, 17 temperature measuring holes, 15 pressure relief holes and 9 heating holes).
The working well construction operation surface is narrow, the holes are densely arranged on the main surface maintenance structure of the working well and need to avoid the structures such as the ring frame beams, and the like, and basically no hole repairing condition is provided. The construction distance of horizontal drilling is as long as 40m, freezing holes are arranged in a divergent mode, the construction accuracy control difficulty is high, and the pore-forming quality requirement is high.
(3) Large cross section of transverse channel
The standard section width of the No. 1 transverse channel is 9.1m, the section form is a gradual change section height from 13.0m to 18.25m, and the maximum section is 166m2. The freezing wall and the primary support are combined to bear, timely support is needed, the primary support and the freezing wall are tightly attached to each other, the primary support and the freezing wall are stressed cooperatively, meanwhile, the excavation time is long, and the creep of the freezing wall and the exposure and temperature rise influence of the excavation face are considered, so that the deformation of the freezing wall is needed to be monitored and controlled strictly in time during excavation.
(4) The freezing excavation period is long, and the frost heaving and thawing settlement control difficulty is high
The frozen volume of the No. 1 transverse channel reaches 8405.76m 3 The freezing time is more than 12 months. The freezing volume is large, the freezing time is long, and the control difficulty of frost heaving and thawing sinking is large.
(5) The workload of clearing the shield crossing freezing pipe is large
Approximately 70 freezing holes in the construction of the No. 1 transverse channel have influence on the subsequent wiring and the crossing of the positive line shield, and the freezing pipe cleaning work is needed after the construction of the transverse channel is finished. The freezing pipe cleaning workload is large, and adverse effects such as pipe breakage and the like can occur in the cleaning process.
(6) Extended end 8m freeze wall quality control
Because the ground at the end part of the No. 1 transverse channel cannot be occupied, the end part of the No. 1 transverse channel is extended by 8m to freeze the wall, and the advanced reinforcement is adopted before the excavation of the end face in cooperation with the development condition of the frozen wall.
3 excavation construction scheme
3.1 construction method
The No. 1 transverse channel adopts a mining method to carry out excavation supporting construction, advanced horizontal grouting reinforcement is carried out in the construction process, and the freezing pipe in the range of the later shield tunnel is pulled out, so that the later shield tunneling is ensured.
The engineering of the embodiment mainly comprises the main working procedures of freezing and pore-forming construction in a No. 1 working well, ground freezing station freezing system installation, stratum freezing reinforcement around a structure, no. 1 transverse channel excavation and construction, frozen pipe pulling-out, filling and melting-down grouting, pipe cutting and hole sealing and the like.
3.2 excavation Process
The No. 1 transverse channel is reinforced by adopting a freezing method outer ring support and assisted by advancing grouting reinforcement of a tunnel face sleeve valve pipe. The construction of the step method is adopted, 4 steps are divided, an operation platform is erected in a No. 1 vertical shaft, excavation is sequentially carried out from top to bottom, after the previous cavity is communicated, the construction of the next cavity is carried out, two steps are excavated in each cavity, and the cyclic footage is 0.5m. And (5) performing primary support in time after excavation. And (5) manually installing an arch frame and a reinforcing steel bar net, and spraying concrete by adopting a wet spraying machine. And (3) after the tunnel is integrally penetrated, performing secondary lining construction from bottom to top. Specifically, according to the design plan, the construction is divided into two freezing steps, namely, freezing the first step and the second step in the first period, and freezing the third step and the fourth step in the second period. And the partition board in each layer of excavation construction is closed into a ring in time along with the excavation and supporting in the excavation process, so that the blank side time is reduced.
Dividing the No. 1 transverse channel into 4 excavation areas according to the arrangement rule of the freezing holes, and horizontally excavating the No. 1 transverse channel from top to bottom in sequence. The excavating steps are as follows:
step 1: drilling according to the planning design of the cylindrical freezing wall, completing drilling construction, installing a freezing system, finishing pressurizing and leakage testing after all freezers are installed, finishing heat preservation construction, finishing salt melting, and starting up for freezing, wherein the figure 8 is shown;
step 2: the first period is actively frozen, the first horizontal grouting is carried out on an unexcavated area which is 10m away from the front end excavation face, the thickness and the average temperature of the frozen wall reach the design requirements, the materials required by excavation are prepared completely, emergency rescue materials are all in place, the excavation acceptance check is passed, and the tunnel excavation construction is prepared, see fig. 9;
step 3: and excavating after finishing horizontal grouting every 10m in sequence, excavating to the end head, and grouting and reinforcing the next step of excavating step area by utilizing the upper space construction vertical grouting holes after the primary support is finished. Excavating a first step, along with excavating and supporting, requiring the time of excavating an exposed surface to be not more than 24 hours, and timely carrying out supporting operation to ensure that the primary support is closely attached to frozen soil, so as to meet the cooperative stress condition, wherein the excavation process is accompanied by tunnel convergence deformation monitoring, as shown in fig. 10;
Step 4: and excavating a second step, wherein the technical requirement is consistent with that of the first step, the time for excavating an exposed surface is not more than 24 hours along with excavating and supporting, supporting operation is required in time, the primary support and frozen soil are guaranteed to be closely attached, the cooperative stress condition is met, and the tunnel convergence deformation monitoring is carried out along with the excavating process. And (5) carrying out horizontal grouting reinforcement after excavating to the end head, and finishing the end reinforcement. Performing next step end capping reinforcement after excavation is completed, as shown in fig. 11;
step 5: and (3) performing positive freezing in the second period, performing third step excavation, and supporting along with excavation, wherein the time for excavating an exposed surface is not more than 24 hours, supporting operation is required in time, the primary support is tightly attached to frozen soil, the cooperative stress condition is met, and tunnel convergence deformation monitoring is performed along with the excavation process. And (5) carrying out horizontal grouting reinforcement after excavating to the end head, and finishing the end reinforcement. Performing next step end capping reinforcement after excavation is completed, as shown in fig. 12;
step 6: and carrying out subsequent complete excavation, along with excavating and supporting, requiring the time of excavating the exposed surface to be not more than 24 hours, and carrying out supporting operation in time, ensuring the primary support to be closely attached to the frozen soil, and meeting the cooperative stress condition. The tunnel convergence deformation monitoring is carried out in the excavation process. Performing horizontal grouting reinforcement after excavating to the end head, and completing the end head reinforcement, as shown in fig. 13;
Step 7: after the water proofing is finished, secondary lining construction is carried out, freezing is stopped, all freezing holes inside and outside are blocked, filling and melting and grouting are carried out, and the figure 14 is shown; after the tunnel is integrally penetrated, a bracket method is adopted, 4 layers are divided from bottom to top, each layer is divided into 3 sections, and two lining construction is carried out.
3.3 horizontal grouting scheme for transverse channels
3.3.1 hole site arrangement
The grouting section length of the 1# transverse channel is 10m, the lap joint is 2.5m, the grouting holes are 1400mmx1400mm, and the quincuncial arrangement is realized. Grouting is sequentially performed from bottom to top and from outside to inside. The grouting hole position is shown in figure 38 in detail.
3.3.2 grouting order
And 2 sets of grouting equipment are adopted for grouting at the same time in each cycle, the grouting sequence is sequentially carried out from bottom to top and from outside to inside, two grouting machines perform grouting on the same horizontal plane, and the grouting hole spacing is more than 2.5m. When grouting, the grouting spray heads cannot be positioned at the same cross section, and the longitudinal and longitudinal staggered distance between the two grouting spray heads is not less than 8m.
3.3.3 grouting pressure
Grouting pressure of the test section is 0.5-1.5 MPa, and the grouting pressure is adjusted according to data analysis of the diffusion radius, grouting pressure, earth surface subsidence, earth surface bulge and the like of the test section in later construction.
3.3.4 grouting mixing ratio
P042.5 ordinary Portland cement is selected, and slurry is selected from: water: cement = 1:1.
3.3.5 grouting preparation
(1) Slurry stopping wall and face seal
The construction steps of the step method are staggered by 5m, and a slurry stopping wall is constructed. The tunnel face is sealed by binding reinforcing steel meshes, arranging anchor pipes and spraying concrete. The steel bar net sheet adopts double-layer net sheets, the diameter is phi 25mm of screw steel, the distance between the net sheets is 250mm multiplied by 250mm, and the steel bar net sheet is welded with the grid arch and the temporary inverted arch section steel in a supporting way. The anchor pipe is made of a common seamless steel pipe with phi 42mm, the length of the anchor pipe is 3.5m, and the transverse-vertical spacing is 1200mm multiplied by 1500mm. The sprayed concrete thickness was 500mm.
(2) Scaffold platform erection
The scaffold is firmly and reliably erected, the scaffold plates are fully paved on the working platform, inspection and acceptance are required after the scaffold is erected, and the scaffold can be used after the operator is subjected to the bottoming training. The scaffold is a multi-row scaffold, and the horizontal and vertical scissor supports are respectively arranged and are connected and fastened by fasteners corresponding to all the vertical rods of the scaffold.
3.3.6 grouting construction flow
(1) Positioning: and fixing the hole site guider according to the set external inserting angle, wherein the hole site deviation is required to be not more than 3cm.
(2) And (3) positioning a drilling machine: the first grouting hole is a 1# hole above, the drilling machine is required to be placed on a temporary scaffold which is erected and accepted, and after the perpendicularity of the drilling rod is adjusted to be aligned with the hole site, the drilling machine cannot be shifted and fixed firmly and cannot be lifted and lowered at will.
(3) Drilling and forming holes: the first hole is constructed to run slowly. The influence of the formation on the drilling machine is mastered to determine drilling parameters under the formation conditions. Closely focusing on the overflow water outlet condition, when a large amount of overflow water outlet occurs, drilling should be stopped immediately, and construction is performed again after analyzing reasons. And checking one section of the drill hole after drilling, correcting the position deviation in time, and finally keeping the position deviation of the bottom of the hole to be not more than 30cm. Drilling and grouting are sequentially performed from bottom to top and from outside to inside.
(4) And (5) back-pumping the drill rod: the lifting amplitude is strictly controlled, each step is not more than 20cm, the grouting is pumped back at a constant speed, and the grouting parameter change is noted.
(5) Proportioning slurry: and carrying out proportioning operation according to the established proportioning parameters, and carrying out proportioning configuration by adopting a calibrated accurate metering tool to ensure that the slurry coagulation time is matched with the proportioning parameters and ensure that the grouting parameters can effectively control the grouting radius to meet the reinforcing requirement.
(6) Grouting: the diameter of the grouting hole is not less than 45mm, the grouting pressure is strictly controlled, the grouting quantity is closely concerned at the same time, when the pressure suddenly rises or overflows from the hole wall and the section surrounding rock, the grouting is stopped immediately, and after the reason is found out, measures such as adjusting grouting parameters or shifting are adopted for re-grouting.
(7) When grouting is about to finish sealing, grouting pressure is controlled to be 0.4-0.8 MPa at the position of the face, grouting flow is controlled, and 1 grade grouting is needed. Avoiding damaging the sealed face due to overlarge grouting pressure. And the grouting parameters are adjusted during sealing, so that no slurry overflow and no slurry leakage are ensured.
(8) The whole grouting process should strengthen construction inspection and monitoring measurement.
(9) The special person takes charge of the operation record of each procedure.
4 construction process and results
The freezing reinforcement project of the No. 1 cross channel of the XXX line XXX section of the rail transit XXX city begins to drill from the XX date of XX year XX month XX, the drilling process is completed in the XX date of XX year XX month XX, 246 freezing holes and 246 temperature measuring holes are completed in an accumulated mode, 9 heating holes and 9 hole supplementing holes are completed, and the figure is 15;
and (3) the frozen system is installed on the XX month XX day XX, and then the whole pipeline system is subjected to water test, so that the tightness is qualified. The XXXX year, XX month and XX day begin to freeze positively, see FIG. 16;
the first step of the No. 1 transverse channel is excavated on the XX month and XX day of the XXXXXX year (see figure 17), and the excavation of the four steps of the No. 1 transverse channel is smoothly completed on the XX month and XX day of the XXXXXX year (see figure 18).
Conclusion 5
The construction method of freezing reinforcement of the No. 1 transverse channel in XX line XX section 1 of the rail transit XX in XXX city and excavation by adopting a freezing method reinforcement and a mining method is adopted, excavation test is safely and smoothly completed within XXX days, and the conclusion obtained by the embodiment mainly comprises the following steps:
(1) The artificial freezing method can effectively enhance the self bearing capacity of surrounding rock, isolate the connection of underground water, and is matched with the mining method excavation mode, so that the engineering can safely and smoothly pass through a region with severe engineering geological conditions.
(2) Parameters of a freezing system must be strictly monitored in the freezing and excavation construction process, if abnormal parameters such as temperature are found, the parameters must be responded immediately, the problem cause is found, and effective measures are taken to solve.
(3) In the excavation construction process of a large-section channel by adopting a manual freezing method, monitoring of sinking deformation of surrounding rock of a vault of the channel and deformation of a side wall should be enhanced, and when abnormal changes exist, the deformation of the vault and the side wall is immediately controlled.
Example 3
As shown in FIG. 19, the combined enclosure structure of the freezing wall and the cement reinforcement in the construction of the large-section tunnel comprises a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and the region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region.
As shown in fig. 37, the frozen soil curtain is a third freezing and reinforcing area 30 formed by arc top and bottom type freezing walls in a 'mesh' -shape; the third freezing reinforcement section 30 includes a third upper freezing wall 301, a third bottom freezing wall 302, a third side freezing wall 303, a third middle intermediate partition freezing wall a304, and a third middle intermediate partition freezing wall B305; the thickness of the third upper freezing wall 301 is 3m, the thickness of the third bottom freezing wall 302 is 3.5m, the thickness of the third side freezing wall 303 is 2.5m, and the thicknesses of the third middle partition freezing wall A304 and the third middle partition freezing wall B305 are 2.5m;
The third upper freezing wall 301, the third bottom freezing wall 302, the third side wall freezing wall 303, the third middle partition freezing wall a304 and the third middle partition freezing wall B305 all extend 8.0m toward the trenchless area along the small section face 5 to be excavated.
The cement grouting body is a cement grouting area 4, the tunnel face 3 of the large-section tunnel to be excavated is composed of three small-section tunnel faces 5 to be excavated which are sequentially arranged from top to bottom, and the cement grouting area 4 is positioned in front of the small-section tunnel faces 5 to be excavated; and the cement grouting area 4 is arranged at intervals of 10m along the excavation direction of the face 5 with the small section to be excavated in the excavation process.
As shown in fig. 27, the freezing holes of the frozen soil curtain are arranged as follows on the longitudinal section of the area to be excavated:
above the area to be excavated: the outer ring auxiliary freezing hole group DN91 is formed by an outer ring freezing hole group D81 formed by 19 outer ring freezing holes and an outer ring auxiliary freezing hole group DN91 formed by 10 outer ring auxiliary freezing holes, wherein the outer ring freezing hole group D81 formed by 7 pressure relief holes, the heating hole group DJ7 formed by 9 heating holes and the outer ring auxiliary freezing hole group D81 formed by 10 outer ring auxiliary freezing holes are sequentially distributed from top to bottom; the pressure relief holes in the pressure relief hole group X6 are distributed at equal intervals along the horizontal direction, the hole spacing between two adjacent pressure relief holes is 1500mm, and the vertical distance L1 between the pressure relief holes and the arc top of the area to be excavated is 4540mm; the heating holes in the heating hole group DJ7 are distributed at equal intervals along the same heating hole group circular arc, the hole interval between two adjacent heating holes is 1500mm, the arc top of the heating hole group circular arc and the arc top of the region to be excavated are on the same vertical line, the distance between the two is 3500mm, and the longitudinal distance L2 from any point on the heating hole group circular arc to the circular arc where the upper edge of the region to be excavated is equal; the 15 outer ring freezing holes in the outer ring freezing hole group D81 are distributed along the same outer ring freezing hole group circular arc, the hole spacing between every two adjacent outer ring freezing holes is 800mm, 1 outer ring freezing hole is distributed on the arc top of the outer ring freezing hole group circular arc, 6 outer ring freezing holes with equal spacing are respectively distributed from the arc top to two sides of the outer ring freezing hole group circular arc, one outer ring freezing hole is respectively arranged at the end point of the outer ring freezing hole group circular arc, and two outer ring freezing holes respectively positioned at two sides of the outer ring freezing hole group circular arc are distributed on the horizontal line between the last outer ring freezing hole and the last outer ring freezing hole at the end of the outer ring freezing hole group circular arc; the arc top of the arc of the outer ring freezing hole group is on the same vertical line with the arc top of the region to be excavated, the distance between the arc top of the arc of the outer ring freezing hole group and the arc top of the region to be excavated is 2400mm, and the longitudinal distance L3 from any point on the arc of the outer ring freezing hole group to the arc where the upper edge of the region to be excavated is located is equal; the 8 outer ring auxiliary freezing holes in the outer ring auxiliary freezing hole group DN91 are distributed on the same outer ring auxiliary freezing hole group circular arc at equal intervals, and the hole spacing between every two adjacent outer ring auxiliary freezing holes is 1200mm; in addition, 2 outer ring auxiliary freezing holes are respectively distributed near the tail end of the outer ring auxiliary freezing hole group arc and are positioned between the outer ring auxiliary freezing hole group arc and the outer ring freezing hole group arc, the arc tops of the outer ring auxiliary freezing hole group arc and the arc tops of the area to be excavated are on the same vertical line, the distance between the two is 877mm, and the longitudinal distance L4 from any point on the outer ring auxiliary freezing hole group arc to the arc where the edge on the area to be excavated is equal;
A first temperature measuring hole, a second temperature measuring hole and a third temperature measuring hole are also distributed above the area to be excavated, the first temperature measuring hole is distributed on the circular arc of the heating hole group and is positioned at the left side of the arc top of the circular arc of the heating hole group, and the second temperature measuring hole and the first temperature measuring hole are on the same horizontal line and are positioned between the circular arc of the heating hole group and the circular arc of the outer ring freezing hole group; the third temperature measuring hole is positioned right below the arc top of the outer ring auxiliary freezing hole group;
left side of the area to be excavated: a first row of outer ring freezing hole groups FB82 and a second row of outer ring freezing hole groups D83 are longitudinally distributed, and the distance between the first row of outer ring freezing hole groups FB82 and the area to be excavated is larger than the distance between the second row of outer ring freezing hole groups D83 and the area to be excavated; the longitudinal straight line where the first column outer ring freezing hole group FB82 is located is also provided with auxiliary freezing holes and temperature measuring holes, the longitudinal straight line where the second column outer ring freezing hole group D83 is located is also provided with auxiliary freezing holes, and the auxiliary freezing holes and the temperature measuring holes are distributed in the area between the second column outer ring freezing hole group D83 and the area to be excavated;
hole groups symmetrical to the left side of the area to be excavated about the longitudinal center line of the area to be excavated are distributed on the right side of the area to be excavated;
in the area to be excavated: the pressure relief device comprises a first pressure relief hole group X61 formed by 2 pressure relief holes, a first interface strengthening freezing hole group G101 formed by 9 interface strengthening freezing holes, a second pressure relief hole group X62 formed by 2 pressure relief holes, a second interface strengthening freezing hole group G102 formed by 5 interface strengthening freezing holes, a third interface strengthening freezing hole group G103 formed by 9 interface strengthening freezing holes, a fourth interface strengthening freezing hole group G104 formed by 5 interface strengthening freezing holes and a third pressure relief hole group X63 formed by 2 pressure relief holes which are distributed in sequence from top to bottom;
The 2 pressure relief holes in the first pressure relief hole group X61 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L5 between the pressure relief holes and the arc top of the area to be excavated is 3924mm, and the hole spacing between the 2 pressure relief holes is 3000mm; the 9 interface strengthening freezing holes in the first interface strengthening freezing hole group G101 are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L51 between the straight line formed by connecting the first interface reinforcing freezing hole groups G101 and the arc top of the area to be excavated is 7742mm, and the hole spacing between two adjacent interface reinforcing freezing holes is 1230mm; the 2 pressure relief holes in the second pressure relief hole group X62 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L7 between the pressure relief holes and the arc top of the area to be excavated is 9522mm, and the hole spacing between the 2 pressure relief holes is 3000mm; the 5 interface strengthening freezing holes in the second interface strengthening freezing hole group G102 are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated; the vertical distance L6 between the straight line formed by connecting the second interface strengthening freezing hole group G102 and the arc top of the area to be excavated is 9742mm, and the hole spacing between two adjacent interface strengthening freezing holes is 2000mm; the 9 interface strengthening freezing holes in the third interface strengthening freezing hole group G103 are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L8 between the straight line formed by connecting the third interface strengthening freezing hole group G103 and the arc top of the area to be excavated is 12742mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm; the 5 interface strengthening freezing holes in the fourth interface strengthening freezing hole group G104 are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated; the vertical distance L9 between a straight line formed by connecting the fourth interface reinforcing freezing hole group G104 and the arc top of the region to be excavated is 13342mm, and the hole spacing between every two adjacent interface reinforcing freezing holes is 1700mm;
The 2 pressure relief holes in the third pressure relief hole group X63 are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L10 between the pressure relief holes and the arc top of the area to be excavated is 13501mm; the hole spacing between the 2 pressure relief holes is 3000mm;
a first row of outer ring auxiliary freezing hole groups DN92 consisting of 9 outer ring auxiliary freezing holes are longitudinally distributed on edge lines on two sides of the area to be excavated;
below the area to be excavated: a third row of outer ring freezing hole groups DB86 formed by 11 outer ring freezing holes, a fourth row of outer ring freezing hole groups DB87 formed by 10 outer ring freezing holes, a fifth row of outer ring freezing hole groups DB88 formed by 11 outer ring freezing holes and a sixth row of outer ring freezing hole groups DB89 formed by 10 outer ring freezing holes are sequentially distributed from top to bottom; 11 outer ring freezing holes in the third row of outer ring freezing hole groups DB86 are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L15 between the straight line formed by connecting the third row of outer ring freezing hole groups DB86 and the arc bottom of the area to be excavated is 14998 mm, and the hole spacing between two adjacent outer ring freezing holes is 1197mm; 10 outer ring freezing holes in the fourth row outer ring freezing hole group DB87 are distributed at equal intervals along the horizontal direction; the vertical distance L16 between a straight line formed by connecting the freezing hole groups DB87 of the fourth row of outer rings and the arc bottom of the region to be excavated is 15308mm, and the hole spacing between two adjacent freezing holes of the outer rings is 1189mm; 11 outer ring freezing holes in the fifth row outer ring freezing hole group DB88 are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L17 between the straight line formed by connecting the freezing hole groups DB88 of the outer ring of the fifth row and the arc bottom of the region to be excavated is 15608mm, and the hole spacing between two adjacent freezing holes of the outer ring is 1197mm; 10 outer ring freezing holes in the sixth row of outer ring freezing hole groups DB89 are distributed at equal intervals along the horizontal direction; the vertical distance L18 between a straight line formed by connecting the freezing hole groups DB89 of the sixth row of outer rings and the arc bottom of the region to be excavated is 15011 mm, and the hole spacing between every two adjacent freezing holes of the outer rings is 1189mm;
A first row of outer ring freezing hole groups DB84 formed by 8 outer ring freezing holes and a second row of outer ring freezing hole groups DB85 formed by 10 outer ring freezing holes are distributed on the edge line of the bottom of the area to be excavated from top to bottom; the outer ring freezing holes in the first row outer ring freezing hole group DB84 are distributed at equal intervals along the horizontal direction, and the vertical distance from the straight line formed by connecting the first row outer ring freezing hole group DB84 to the straight line formed by connecting the third row outer ring freezing hole group DB86 is L11; the outer ring freezing holes in the second row outer ring freezing hole group DB85 are distributed at equal intervals in the horizontal direction, and the vertical distance from the straight line formed by the second row outer ring freezing hole group DB85 to the straight line formed by the third row outer ring freezing hole group DB86 is L12.
Example 4
Compared with other small-section tunnel engineering, the construction difficulty is higher, the construction risk is more, and a great number of engineering technical problems still exist in the extra-large-section tunnel engineering. Among them, how to select reasonable and safe construction method to pass through stratum with complex condition is a special concern for all parties of engineering construction. At the same time, the problem is one of the hot spots of research in the academic community. In order to build tunnels in weak strata, scientific researchers at home and abroad propose a plurality of stratum reinforcing methods, and technologies such as grouting, small guide pipes, pipe sheds and the like are commonly applied in soil tunnels. The artificial freezing method is used as a temporary reinforcement technology and is widely applied to mine construction and municipal engineering, but the application experience in tunnel engineering with extra large section is still insufficient.
In the embodiment, a freezing method and a grouting method are combined, and a combined building envelope method of 'freezing wall + cement reinforcing body' in the embodiment 3 is adopted, and in the embodiment 2, construction test is carried out on the combined building envelope by taking a 2# transverse channel freezing project of a tunnel between a XXX line XXX station and a XXX station of a subway XXX city as an example.
The construction of the 2# working well is completed, and the construction method of reinforcing the XXX section 2# transverse channel by a freezing method and underground excavation by a mining method is adopted because the water inflow of the stratum near the 2# working well is large, the sand content of the soil layer is large, the self stability is poor and the open excavation condition is not provided.
6 engineering overview
6.1 engineering content is the same as in example 2.
6.2 engineering geology and hydrogeology
6.2.1 topographical features were identical to example 2.
6.2.2 engineering geology
The 2# transverse channel mainly penetrates through the hard plastic sandy cohesive soil layer <5Z-2>, and sandy cohesive soil <7Z-B >. The thickness of the top soil of the transverse channel is 7m. The geological condition of the interval is complex, and the lower bedrock is mainly various rocks such as clastic rock, carbonaceous shale, carbonaceous limestone, mixed granite and the like. The engineering mixed granite residual soil of the embodiment can be divided into plastic sandy cohesive soil (5Z-1) and hard plastic sandy cohesive soil (5Z-2).
The number 2 transverse channel is mainly used for crossing the poor geological zone: residual earth formations, sand liquefaction, and the like.
(1) Ground subsidence: filling soil (1) and mucky soil (4-2 b) are distributed on the ground surface in the field, and if frost heaving of a transverse channel is excessive, turf cracking damage in the foot lake golf course can be caused.
(2) Ground collapse: the bottom of the No. 2 transverse channel penetrates through the mixed granite residual soil stratum, the stratum is mainly hard plastic sandy cohesive soil, the full weathering is hard soil, the stratum is easy to disintegrate when meeting water, engineering water properties are poor, surrounding rock stability is poor, and collapse accidents can be induced if a freezing wall and a supporting structure are improper and the combined system is seriously deformed.
(3) Disturbance of the formation: the 2# transverse channel is mainly artificial filled soil, sandy clay, residual soil, full and strong weathered mixed granite, and has poor overall mechanical properties, and is easy to soften and disintegrate when meeting water.
6.2.3 hydrogeology
The water level of the underground water disclosed by the 2# horizontal channel range investigation is shallower, the water level burial depth is 1.80-18.10 m, the change of the underground water level is closely related to occurrence, supply and drainage of the underground water level and is influenced by seasonal change, the water level is obviously increased in the supply period of the underground water within 4-9 months each year, the consumption period and the drainage period of the underground water within 10-3 months each year, the underground water level is reduced along with the water level, and the annual change range is 2.5-3.0 m. The underground water is divided into fourth-series soil layer pore water, lamellar bedrock fracture water, blocky bedrock fracture water and carbonate rock fracture karst cave water according to the occurrence mode.
6.3 2# transverse channel structure
The 2# working well size is length x width=12m×11.1m, bottom hole elevation 7.431m, surface elevation 34.000m. The maintenance structure of the No. 2 working well is an underground diaphragm wall with the thickness of 800mm, and ring frame beams with the width of 4 channels and the height of 1.8m and 1.5m are arranged in the underground diaphragm wall. And constructing the freezing holes of the No. 2 transverse channels on the main surface of the maintenance structure of the working well, and avoiding the ring frame beams in drilling construction. The length of the 2# transverse channel is 30.00m, the 2# transverse channel is a variable cross section, as shown in fig. 23, the cross section of the inlet channel B-B is 9.7m wide, the height is 12.75m, the cross section of the channel end D-D is 9.7m wide, and the height is 17.00m.
The 2# transverse channel excavation is divided into three steps, each layer of excavation construction middle partition plate is composed of I25a section steel and C25 sprayed concrete with the thickness of 320 mm. The primary support of the No. 2 transverse channel is C25P6 shotcrete with the thickness of 350mm and a grid steel frame, and the secondary lining structure is C35P6 impervious concrete with the thickness of 700 mm.
7 'freezing wall + cement reinforcing body' combined enclosure structure and excavation method
The freezing method for reinforcing the stratum has the outstanding advantages that: the frozen soil curtain has good uniformity, tight combination with the maintenance structure wall, good reinforcement effect and safe and reliable construction. But the end sealing adopts filling reinforcement, the number of freezing holes is large, the excavation difficulty is large, and the engineering cost is high. Grouting is an effective technical means for preventing and curing underground engineering water damage and reinforcing weak stratum, but the single use risk is high.
The combined enclosure structure of the freezing wall and the cement reinforcing body combines the freezing method and the grouting method, fully exerts the advantages of the freezing method and the grouting method, and eliminates the disadvantages of the freezing method and the grouting method; the outer ring of the tunnel adopts a freezing reinforcement method, namely the outer ring is in a cylindrical freezing wall form, so that soil bodies in the range of the peripheral freezing wall of the constructed tunnel are frozen and reinforced, a frozen soil curtain with high strength is formed, and a weak freezing area is formed in an excavated area. The end adopts horizontal grouting to consolidate, can seal the groundwater of end, guarantees to freeze the reinforcement effect, and drilling quantity reduces by a wide margin moreover, and the excavation degree of difficulty is showing and is reducing. In order to control formation deformation caused by freeze thawing of soil layers, tracking grouting is needed in the thawing process of a freezing and reinforcing area. The monitoring of deformation and freezing system parameters is enhanced in the whole construction process.
7.1 freezing wall Structure
The 2# transverse channel adopts a straight wall arc top-bottom type freezing wall, the thickness of the upper freezing wall is 3m, the thickness of the side wall freezing wall is 2.5m, the thickness of the bottom plate freezing wall is 3.5m, and the freezing wall at the front end excavation face extends for 8m. The 2# transverse channel freeze walls are shown in fig. 24, 25a and 25b.
The construction freezing holes are divided into outer ring freezing holes D, DB and FB, an outer ring auxiliary freezing hole DN and an interface reinforcing freezing hole G; temperature measurement hole C, release hole X, heating hole DJ. The arrangement of the 2# transverse channel freezing holes is shown in fig. 26a and 26b, and the opening positions are shown in fig. 27.
7.2 freeze design parameters
The main parameters of the freezing design are shown in Table 2:
TABLE 2
7.3 construction emphasis and difficulty
(1) Engineering geological risk
The No. 2 transverse channel is positioned in the hard plastic sandy cohesive soil layer <5Z-2>, <7Z-B > sandy cohesive soil, most of the transverse channel is positioned in the hard plastic sandy cohesive soil layer <5Z-2>, <7Z-B > sandy cohesive soil, the soil layer is disintegrated by water, the sand content is larger, and the phenomena of sand burst, mud bleeding and the like easily occur in drilling holes; the bottom is located on the middle weathered rock, the bottom is frozen Kong Jishao and partially embedded on the hard rock, and the drilling construction difficulty is high.
(2) Difficulty in drilling construction
The number of frozen holes of the No. 2 transverse channel is up to 251 (including 213 frozen holes, 16 temperature measuring holes, 13 pressure relief holes and 9 heating holes).
The working well construction operation surface is narrow, the holes are densely arranged on the main surface maintenance structure of the working well and need to avoid the structures such as the ring frame beams, and the like, and basically no hole repairing condition is provided. The construction distance of horizontal drilling is as long as 38.8m, freezing holes are arranged in a divergent mode, the construction accuracy control difficulty is high, and the pore-forming quality requirement is high.
(3) Large cross section of transverse channel
The standard section width of the No. 2 transverse channel is 9.7m, the section form is a gradual change section height from 12.75m to 17.00m, and the maximum section is 166m2. The engineering of this embodiment considers freezing wall and primary support and jointly bears, needs in time support to guarantee that primary support and freezing wall closely laminate, cooperate the atress, excavation time is long simultaneously, considers freezing wall creep and excavation face and expose the intensification influence, so must in time support when excavating, strict control freezes wall deformation.
(4) The freezing excavation period is long, and the frost heaving and thawing settlement control difficulty is high
The frozen volume of the 2# transverse channel reaches 6346.76m 3 The freezing time is more than 12 months. The freezing volume is large, the freezing time is long, and the control difficulty of frost heaving and thawing sinking is large.
(5) The workload of clearing the shield crossing freezing pipe is large
Approximately 70 freezing holes in the construction of the No. 2 transverse channel have influence on the subsequent wiring and the crossing of the positive line shield, and the freezing pipe cleaning work is needed after the construction of the transverse channel is finished. The freezing pipe cleaning workload is large, and adverse effects such as pipe breakage and the like can occur in the cleaning process.
(6) The quality control difficulty of the frozen wall with the extension end part of 8m is great
Because the ground at the end part of the 2# transverse channel cannot be occupied, the end part of the 2# transverse channel is extended by 8m to freeze the wall, and the advanced reinforcement is adopted before the excavation of the end face in cooperation with the development condition of the frozen wall.
8 excavation construction scheme
8.1 construction method
The 2# transverse channel adopts a mining method to divide steps to carry out excavation supporting construction, a construction platform is erected in a vertical shaft, full-section advanced grouting reinforcement of each step is carried out on the platform, and after the grouting and freezing reinforcement effects meet the design requirements through inspection, the underground continuous wall hole entering excavation construction is broken. Namely: and (5) adopting a freezing method to support and strengthen the outer ring. The construction of the step method is adopted, 3 steps are divided, an operation platform is erected in a No. 2 vertical shaft, excavation is sequentially carried out from top to bottom, construction of the next cavity is carried out after the previous cavity is communicated, the steps in each cavity are excavated, and the cyclic footage is 0.5m. And after excavation, performing primary support and primary spraying in time. The sprayed concrete adopts wet spraying machine operation, and the anchor rods, the arch frames and the reinforcing steel bar net are manually installed. And after the tunnel is integrally penetrated, performing secondary lining construction from bottom to top, and performing shield hoisting to influence part of the reserved reinforcing steel bars to support.
8.2 excavation Process
And the 2# transverse channel excavation construction divides the excavation into 3 areas according to the arrangement rule of the freezing holes, and horizontal excavation is carried out from top to bottom in sequence. And the partition board in each layer of excavation construction is closed into a ring in time along with the excavation and supporting in the excavation process, so that the blank side time is reduced. The excavating steps are as follows:
step 1: and (3) finishing drilling construction, namely finishing pressing and leakage testing after all freezers are installed, and finishing heat preservation construction. After salt dissolution is finished, starting up and freezing; see fig. 28.
Step 2: the method comprises the steps of actively freezing, enabling the thickness of a frozen wall and the average temperature to meet the design requirements, grouting reinforcement, complete preparation of materials required by excavation, complete in-place emergency rescue materials, and preparation of tunnel excavation construction through excavation acceptance; see fig. 29.
Step 3: and excavating a first partition until the primary support is completed. And grouting and reinforcing the next step area by utilizing the upper space construction vertical grouting holes. The first step is excavated, the time for excavating the exposed surface is not more than 24 hours along with the excavation and supporting, the supporting operation is required to be carried out in time, the primary support is guaranteed to be closely attached to the frozen soil, the cooperative stress condition is met, and the tunnel convergence deformation monitoring is carried out along with the excavation process; see fig. 30.
Step 4: the second step is reinforced by horizontal grouting, the technical requirement is consistent with that of the first step after the reinforcement is completed, the time for excavating an exposed surface is required to be no more than 24 hours along with the excavation, the support operation is required to be performed in time, the primary support is guaranteed to be closely attached to frozen soil, the cooperative stress condition is met, the tunnel convergence deformation monitoring is carried out during the excavation, and the third step at the lower part is reinforced after the end is excavated; see fig. 31.
Step 5: adopting the same technical requirements, carrying out horizontal grouting reinforcement, carrying out excavation, excavating a third step, carrying out excavation along with supporting, wherein the time for excavating an exposed surface is required to be not more than 24 hours, supporting operation is required to be carried out in time, the primary support is guaranteed to be closely attached to frozen soil, the cooperative stress condition is met, and the tunnel convergence deformation monitoring is carried out in the excavation process; see fig. 32.
Step 6: after the water proofing is finished, secondary lining construction is carried out, freezing is stopped, all freezing holes inside and outside are plugged, and filling, melting, sinking and grouting are carried out; see fig. 33.
And (3) secondary lining construction: after the tunnel is integrally penetrated, constructing the lining wall in a layered manner from bottom to top by adopting a bracket method, and reserving a middle plate lap joint reinforcing steel bar of a negative two layers; constructing the lining wall to 0.2m below the temporary opposite bracing bottom surface, erecting a temporary support for the second lining, dismantling the temporary opposite bracing of the I-steel sprayed concrete, and constructing a negative first middle plate; constructing the residual lining wall and the vault, and sealing the two linings into a ring; disassembling and hanging the shield machine, and sequentially disassembling the temporary support; and after the shield machine is lifted out, recovering the middle plate and the partition wall in the negative two layers.
9 construction process and results
The freezing reinforcement project of the 2# cross channel in the XXX line XXX section of the rail transit XXX city starts to drill from the XX date of XX year XX month XX, the drilling process is completed in the XX date of XX year XX month XX, 248 freezing holes and 248 temperature measuring holes are completed in an accumulated mode, 9 heating holes and 15 hole supplementing holes are completed, and the figure is 34.
And after the freezing system is installed in 12 months and 30 days in 2019, water test is carried out on the whole pipeline system, and the tightness is qualified. Positive freezing starts at 1 month and 10 days 2020, see FIG. 35.
The first step of the No. 2 transverse channel is excavated from 5 months to 1 month in 2020 to 18 months in 2020, and the excavation of the three steps of the No. 2 transverse channel is smoothly completed, as shown in fig. 36.
Conclusion 10
The construction of the 2# cross channel freezing reinforcement project in the XXX line XXX section of the rail transit XXX city adopts a freezing wall and cement reinforcing body combined enclosing structure and an excavation method, the excavation is safely and smoothly completed, and the conclusion obtained by the embodiment mainly comprises the following steps:
(1) The combined enclosure structure of the freezing wall and the cement reinforcing body not only effectively enhances the bearing capacity of surrounding rock, but also isolates the connection of underground water, and the combined enclosure structure is matched with a mining method step excavation mode, so that the combined enclosure structure can safely and smoothly pass through a section with complex stratum conditions, and the design parameters and the excavation supporting scheme of the combined enclosure structure of the freezing wall and the cement reinforcing body are reasonable, so that the construction safety of a transverse channel engineering is ensured.
(2) The end horizontal grouting technology can effectively solve the problem of water sealing of an end area, cuts off the connection between the end area and underground water, and ensures the safety during excavation and structure pouring.
(3) The whole construction process must strictly monitor parameters of the freezing system and the freezing wall, if the parameters of the freezing system such as temperature are found to be abnormal, the problem causes must be immediately found, and effective measures are taken to solve the problem.
(4) And when abnormal changes occur, corresponding measures are adopted immediately to control the deformation of the vault and the side wall.
Claims (7)
1. The combined enclosure structure of the freezing wall and the cement reinforcement in the construction of the large-section tunnel is characterized by comprising a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and a region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region; the cement reinforcement body is positioned in surrounding rock of the tunnel face (3) of the large-section tunnel to be excavated along the excavation direction;
the frozen soil curtain comprises a first-period freezing and reinforcing area (1) and a second-period freezing and reinforcing area (2); the first-stage freezing reinforcement area (1) is a ' Chinese character ' ri ' shaped straight wall arc top-bottom type freezing wall; the first-stage freezing and reinforcing zone (1) comprises a first upper freezing wall (11), a first bottom middle partition freezing wall (12), a first side wall freezing wall (13) and a first middle partition freezing wall (14); the first upper freezing wall (11), the first bottom middle partition freezing wall (12), the first side wall freezing wall (13) and the first middle partition freezing wall (14) extend towards a non-excavation area along the small-section tunnel face (5) to be excavated;
The second-stage freezing reinforcement area (2) is a straight wall arc bottom type freezing wall in a Chinese character 'ri'; the second-stage freezing and reinforcing zone (2) comprises a second upper freezing wall (21), a second bottom freezing wall (22), a second side wall freezing wall (23) and a second middle partition plate freezing wall (24); the second upper freezing wall (21) is connected with the first bottom middle partition freezing wall (12) of the first period freezing reinforcement zone (1); the second upper freezing wall (21), the second bottom freezing wall (22), the second side wall freezing wall (23) and the second middle partition plate freezing wall (24) extend towards a non-excavation area along the small-section tunnel face (5) to be excavated;
the freezing holes of the frozen soil curtain are distributed on the longitudinal section of the area to be excavated as follows:
above the area to be excavated: the outer ring auxiliary freezing hole group DN (91) is formed by an outer ring freezing hole group D (81) formed by 19 outer ring freezing holes and an outer ring auxiliary freezing hole group DN (91) formed by 10 outer ring auxiliary freezing holes, wherein the pressure relief hole group X (6) formed by 7 pressure relief holes, the heating hole group DJ (7) formed by 9 heating holes and the outer ring auxiliary freezing hole group D (81) formed by 10 outer ring freezing holes are sequentially distributed from top to bottom;
the pressure relief holes in the pressure relief hole group X (6) are distributed at equal intervals along the horizontal direction, the hole spacing between two adjacent pressure relief holes is 1500mm, and the vertical distance L1 between the pressure relief holes and the arc top of the area to be excavated is 6800mm;
The heating holes in the heating hole group DJ (7) are distributed at equal intervals along the same heating hole group circular arc, the hole interval between two adjacent heating holes is 1500mm, the arc tops of the heating hole group circular arcs and the arc tops of the areas to be excavated are on the same vertical line, the distance between the two is 5460mm, and the longitudinal distance L2 from any point on the heating hole group circular arc to the circular arc where the upper edge of the area to be excavated is equal;
15 outer ring freezing holes in the outer ring freezing hole group D (81) are distributed along the same outer ring freezing hole group circular arc, 1 outer ring freezing hole is distributed on the arc top of the outer ring freezing hole group circular arc, 6 equally spaced outer ring freezing holes are respectively distributed from the arc top to two sides of the outer ring freezing hole group circular arc, the hole spacing between two adjacent outer ring freezing holes in the 6 equally spaced outer ring freezing holes is 800mm, one outer ring freezing hole is respectively arranged at the end point of the outer ring freezing hole group circular arc, and two outer ring freezing holes respectively positioned at two sides of the outer ring freezing hole group circular arc are distributed on the horizontal line between the outer ring freezing hole and the last first outer ring freezing hole and the last second outer ring freezing hole at the end point of the outer ring freezing hole group circular arc; the arc top of the outer ring freezing hole group arc and the arc top of the area to be excavated are on the same vertical line, the distance between the arc top of the outer ring freezing hole group arc and the arc top of the area to be excavated is 4660mm, and the longitudinal distance L3 from any point on the outer ring freezing hole group arc to the arc where the upper edge of the area to be excavated is located is equal;
8 outer ring auxiliary freezing holes in the outer ring auxiliary freezing hole group DN (91) are distributed on the same outer ring auxiliary freezing hole group circular arc at equal intervals, and the hole spacing between two adjacent outer ring auxiliary freezing holes is 1200mm; in addition, 2 outer ring auxiliary freezing holes are respectively distributed near the tail end of the outer ring auxiliary freezing hole group circular arc and are positioned between the outer ring auxiliary freezing hole group circular arc and the outer ring freezing hole group circular arc, the arc tops of the outer ring auxiliary freezing hole group circular arc and the arc tops of the to-be-excavated area are on the same vertical line, the distance between the two is 3160mm, and the longitudinal distance L4 from any point on the outer ring auxiliary freezing hole group circular arc to the circular arc where the upper edge of the to-be-excavated area is equal;
a first temperature measuring hole, a second temperature measuring hole and a third temperature measuring hole are also distributed above the area to be excavated, the first temperature measuring hole is distributed on the circular arc of the heating hole group and is positioned at the left side of the arc top of the circular arc of the heating hole group, and the second temperature measuring hole and the first temperature measuring hole are on the same horizontal line and are positioned between the circular arc of the heating hole group and the circular arc of the outer ring freezing hole group; the third temperature measuring hole is positioned right below the arc top of the outer ring auxiliary freezing hole group;
Left side of the area to be excavated: a first row of outer ring freezing hole groups FB (82) and a second row of outer ring freezing hole groups D (83) are longitudinally distributed, and the distance between the first row of outer ring freezing hole groups FB (82) and the area to be excavated is larger than the distance between the second row of outer ring freezing hole groups D (83) and the area to be excavated; auxiliary freezing holes and temperature measuring holes are further formed in the longitudinal straight line of the first column of outer ring freezing hole groups FB (82), auxiliary freezing holes are further formed in the longitudinal straight line of the second column of outer ring freezing hole groups D (83), and auxiliary freezing holes and temperature measuring holes are distributed in the area between the second column of outer ring freezing hole groups D (83) and the area to be excavated;
hole groups symmetrical to the left side of the area to be excavated about the longitudinal center line of the area to be excavated are distributed on the right side of the area to be excavated;
in the area to be excavated: the device comprises a first pressure relief hole group X (61) formed by 2 pressure relief holes, a first interface strengthening freezing hole group G (101) formed by 7 interface strengthening freezing holes, a second interface strengthening freezing hole group G (102) formed by 4 interface strengthening freezing holes, a second pressure relief hole group X (62) formed by 2 pressure relief holes, a third interface strengthening freezing hole group G (103) formed by 7 interface strengthening freezing holes, a fourth interface strengthening freezing hole group G (104) formed by 8 interface strengthening freezing holes, a third pressure relief hole group X (63) formed by 2 pressure relief holes, a fifth interface strengthening freezing hole group G (105) formed by 7 interface strengthening freezing holes and a fourth pressure relief hole group X (64) formed by 2 pressure relief holes, which are distributed from top to bottom;
2 pressure relief holes in the first pressure relief hole group X (61) are symmetrically distributed on two sides of a longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L5 between the pressure relief holes and the arc top of the area to be excavated is 782mm, and the hole spacing between the 2 pressure relief holes is 3000mm;
7 interface strengthening freezing holes in the first interface strengthening freezing hole group G (101) are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L51 between the straight line formed by connecting the first interface strengthening freezing hole group G (101) and the arc top of the area to be excavated is 5300mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm;
the 4 interface strengthening freezing holes in the second interface strengthening freezing hole group G (102) are formed in the way of equidistant and symmetrical distribution on two sides of the longitudinal central axis of the region to be excavated along the horizontal direction; the vertical distance L6 between the straight line formed by connecting the second interface strengthening freezing hole group G (102) and the arc top of the region to be excavated is 6103mm, and the hole spacing between two adjacent interface strengthening freezing holes is 2000mm;
2 pressure relief holes in the second pressure relief hole group X (62) are symmetrically distributed on two sides of a longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L7 between the pressure relief holes and the arc top of the area to be excavated is 7384mm; the hole spacing between the 2 pressure relief holes is 3000mm;
7 interface strengthening freezing holes in the third interface strengthening freezing hole group G (103) are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L8 between the straight line formed by connecting the third interface strengthening freezing hole group G (103) and the arc top of the region to be excavated is 10303mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm;
the 8 interface strengthening freezing holes in the fourth interface strengthening freezing hole group G (104) are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the region to be excavated; the vertical distance L9 between the straight line formed by connecting the fourth interface strengthening freezing hole group G (104) and the arc top of the region to be excavated is 11000mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1200mm;
2 pressure relief holes in the third pressure relief hole group X (63) are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L10 between the pressure relief holes and the arc top of the area to be excavated is 11172mm; the hole spacing between the 2 pressure relief holes is 3000mm;
7 interface strengthening freezing holes in the fifth interface strengthening freezing hole group G (105) are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L11 between the straight line formed by connecting the fifth interface strengthening freezing hole group G (105) and the arc top of the area to be excavated is 11853mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm;
2 pressure relief holes in the fourth pressure relief hole group X (64) are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L12 between the pressure relief holes and the arc top of the area to be excavated is 12262mm; the hole spacing between the 2 pressure relief holes is 3000mm;
a fourth temperature measuring hole, a fifth temperature measuring hole, a sixth temperature measuring hole and a seventh temperature measuring hole are further formed in the region to be excavated, 4 temperature measuring holes are formed in the longitudinal central axis of the region to be excavated, and the fourth temperature measuring hole is located between the first interface reinforced freezing hole group G (101) and the second interface reinforced freezing hole group G (102); the fifth temperature measuring hole is positioned on a straight line formed by connecting the fourth interface reinforced freezing hole group G (104); the sixth temperature measurement hole is positioned between the third pressure relief hole group X (63) and the fifth interface-enhanced freezing hole group G (105); the seventh temperature measurement hole is positioned below the fourth pressure relief hole group X (64);
a first row of outer ring auxiliary freezing hole groups DN (92) consisting of 4 outer ring auxiliary freezing holes are longitudinally distributed at the edges of two sides of the region to be excavated;
below the area to be excavated: a first row of outer ring freezing hole groups DB (84) formed by 11 outer ring freezing holes, a second row of outer ring freezing hole groups DB (85) formed by 10 outer ring freezing holes, a third row of outer ring freezing hole groups DB (86) formed by 11 outer ring freezing holes, a fourth row of outer ring freezing hole groups DB (87) formed by 10 outer ring freezing holes and a fifth row of outer ring freezing hole groups DB (88) formed by 11 outer ring freezing holes are sequentially distributed from top to bottom;
11 outer ring freezing holes in the first row of outer ring freezing hole groups DB (84) are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L13 between a straight line formed by connecting the first row of outer ring freezing hole groups DB (84) and the arc bottom of the region to be excavated is 13133mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm;
10 outer ring freezing holes in the second row outer ring freezing hole group DB (85) are distributed at equal intervals along the horizontal direction; the vertical distance L14 between a straight line formed by connecting the second row of outer ring freezing hole groups DB (85) and the arc bottom of the region to be excavated is 13463mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm;
11 outer ring freezing holes in the third row of outer ring freezing hole groups DB (86) are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L15 between a straight line formed by connecting the third row of outer ring freezing hole groups DB (86) and the arc bottom of the region to be excavated is 13760mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm;
10 outer ring freezing holes in the fourth row outer ring freezing hole group DB (87) are distributed at equal intervals along the horizontal direction; the vertical distance L16 between a straight line formed by connecting the fourth row of outer ring freezing hole groups DB (87) and the arc bottom of the region to be excavated is 14163mm, and the hole spacing between two adjacent outer ring freezing holes is 1200mm;
11 outer ring freezing holes in the fifth row outer ring freezing hole group DB (88) are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L17 between a straight line formed by connecting the freezing hole groups DB (88) of the outer ring of the fifth row and the arc bottom of the region to be excavated is 14463mm, and the hole spacing between every two adjacent freezing holes of the outer ring is 1200mm.
2. The combined enclosure structure of the freezing wall and the cement reinforcement in the construction of the large-section tunnel is characterized by comprising a frozen soil curtain and a cement reinforcement body; the frozen soil curtain is a cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and a region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region; the cement reinforcement body is positioned in surrounding rock of the tunnel face (3) of the large-section tunnel to be excavated along the excavation direction;
the frozen soil curtain is a third freezing reinforcement area (30) formed by arc top and bottom type freezing walls in a 'mesh' -shape; the third freezing and reinforcing region (30) comprises a third upper freezing wall (301), a third bottom freezing wall (302), a third side wall freezing wall (303), a third middle partition plate freezing wall A (304) and a third middle partition plate freezing wall B (305); the third upper freezing wall (301), the third bottom freezing wall (302), the third side wall freezing wall (303), the third middle partition plate freezing wall A (304) and the third middle partition plate freezing wall B (305) all extend to a non-excavation area along a small-section tunnel face (5) to be excavated;
The freezing holes of the frozen soil curtain are distributed on the longitudinal section of the area to be excavated as follows:
above the area to be excavated: the outer ring auxiliary freezing hole group DN (91) is formed by an outer ring freezing hole group D (81) formed by 19 outer ring freezing holes and an outer ring auxiliary freezing hole group DN (91) formed by 10 outer ring auxiliary freezing holes, wherein the pressure relief hole group X (6) formed by 7 pressure relief holes, the heating hole group DJ (7) formed by 9 heating holes and the outer ring auxiliary freezing hole group D (81) formed by 10 outer ring freezing holes are sequentially distributed from top to bottom;
the pressure relief holes in the pressure relief hole group X (6) are distributed at equal intervals along the horizontal direction, the hole spacing between two adjacent pressure relief holes is 1500mm, and the vertical distance L1 between the pressure relief holes and the arc top of the area to be excavated is 4540mm;
the heating holes in the heating hole group DJ (7) are distributed at equal intervals along the same heating hole group circular arc, the hole interval between two adjacent heating holes is 1500mm, the arc tops of the heating hole group circular arcs and the arc tops of the areas to be excavated are on the same vertical line, the distance between the two is 3500mm, and the longitudinal distance L2 from any point on the heating hole group circular arc to the circular arc where the upper edge of the area to be excavated is equal;
15 outer ring freezing holes in the outer ring freezing hole group D (81) are distributed along the same outer ring freezing hole group circular arc, 1 outer ring freezing hole is distributed on the arc top of the outer ring freezing hole group circular arc, 6 equally spaced outer ring freezing holes are respectively distributed from the arc top to two sides of the outer ring freezing hole group circular arc, the hole spacing between two adjacent outer ring freezing holes in the 6 equally spaced outer ring freezing holes is 800mm, one outer ring freezing hole is respectively arranged at the end point of the outer ring freezing hole group circular arc, and two outer ring freezing holes respectively positioned at two sides of the outer ring freezing hole group circular arc are distributed on the horizontal line between the outer ring freezing hole and the last first outer ring freezing hole and the last second outer ring freezing hole at the end point of the outer ring freezing hole group circular arc; the arc top of the outer ring freezing hole group arc and the arc top of the area to be excavated are on the same vertical line, the distance between the arc top of the outer ring freezing hole group arc and the arc top of the area to be excavated is 2400mm, and the longitudinal distance L3 from any point on the outer ring freezing hole group arc to the arc where the upper edge of the area to be excavated is located is equal;
8 outer ring auxiliary freezing holes in the outer ring auxiliary freezing hole group DN (91) are distributed on the same outer ring auxiliary freezing hole group circular arc at equal intervals, and the hole spacing between two adjacent outer ring auxiliary freezing holes is 1200mm; in addition, 2 outer ring auxiliary freezing holes are respectively distributed near the tail end of the outer ring auxiliary freezing hole group circular arc and are positioned between the outer ring auxiliary freezing hole group circular arc and the outer ring freezing hole group circular arc, the arc tops of the outer ring auxiliary freezing hole group circular arc and the arc tops of the to-be-excavated area are on the same vertical line, the distance between the two is 877mm, and the longitudinal distance L4 from any point on the outer ring auxiliary freezing hole group circular arc to the circular arc where the upper edge of the to-be-excavated area is equal;
a first temperature measuring hole, a second temperature measuring hole and a third temperature measuring hole are also distributed above the area to be excavated, the first temperature measuring hole is distributed on the circular arc of the heating hole group and is positioned at the left side of the arc top of the circular arc of the heating hole group, and the second temperature measuring hole and the first temperature measuring hole are on the same horizontal line and are positioned between the circular arc of the heating hole group and the circular arc of the outer ring freezing hole group; the third temperature measuring hole is positioned right below the arc top of the outer ring auxiliary freezing hole group;
Left side of the area to be excavated: a first row of outer ring freezing hole groups FB (82) and a second row of outer ring freezing hole groups D (83) are longitudinally distributed, and the distance between the first row of outer ring freezing hole groups FB (82) and the area to be excavated is larger than the distance between the second row of outer ring freezing hole groups D (83) and the area to be excavated; auxiliary freezing holes and temperature measuring holes are further formed in the longitudinal straight line of the first column of outer ring freezing hole groups FB (82), auxiliary freezing holes are further formed in the longitudinal straight line of the second column of outer ring freezing hole groups D (83), and auxiliary freezing holes and temperature measuring holes are distributed in the area between the second column of outer ring freezing hole groups D (83) and the area to be excavated;
hole groups symmetrical to the left side of the area to be excavated about the longitudinal center line of the area to be excavated are distributed on the right side of the area to be excavated;
in the area to be excavated: a first pressure relief hole group X (61) formed by 2 pressure relief holes, a first interface strengthening freezing hole group G (101) formed by 9 interface strengthening freezing holes, a second pressure relief hole group X (62) formed by 2 pressure relief holes, a second interface strengthening freezing hole group G (102) formed by 5 interface strengthening freezing holes, a third interface strengthening freezing hole group G (103) formed by 9 interface strengthening freezing holes, a fourth interface strengthening freezing hole group G (104) formed by 5 interface strengthening freezing holes and a third pressure relief hole group X (63) formed by 2 pressure relief holes are distributed from top to bottom in sequence;
2 pressure relief holes in the first pressure relief hole group X (61) are symmetrically distributed on two sides of a longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L5 between the pressure relief holes and the arc top of the area to be excavated is 3924mm, and the hole spacing between the 2 pressure relief holes is 3000mm;
9 interface strengthening freezing holes in the first interface strengthening freezing hole group G (101) are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the area to be excavated; the vertical distance L51 between the straight line formed by connecting the first interface strengthening freezing hole group G (101) and the arc top of the area to be excavated is 7742mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm;
2 pressure relief holes in the second pressure relief hole group X (62) are symmetrically distributed on two sides of a longitudinal central axis of the area to be excavated along the horizontal direction, the vertical distance L7 between the pressure relief holes and the arc top of the area to be excavated is 9522mm, and the hole spacing between the 2 pressure relief holes is 3000mm;
the 5 interface strengthening freezing holes in the second interface strengthening freezing hole group G (102) are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the region to be excavated; the vertical distance L6 between the straight line formed by connecting the second interface strengthening freezing hole group G (102) and the arc top of the region to be excavated is 9742mm, and the hole spacing between two adjacent interface strengthening freezing holes is 2000mm;
9 interface strengthening freezing holes in the third interface strengthening freezing hole group G (103) are distributed at equal intervals along the horizontal direction, and one interface strengthening freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L8 between the straight line formed by connecting the third interface strengthening freezing hole group G (103) and the arc top of the region to be excavated is 12742mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1230mm;
the 5 interface strengthening freezing holes in the fourth interface strengthening freezing hole group G (104) are formed in the mode of being equally spaced along the horizontal direction and symmetrically distributed on two sides of the longitudinal central axis of the region to be excavated; the vertical distance L9 between a straight line formed by connecting the fourth interface strengthening freezing hole group G (104) and the arc top of the region to be excavated is 13342mm, and the hole spacing between two adjacent interface strengthening freezing holes is 1700mm;
2 pressure relief holes in the third pressure relief hole group X (63) are symmetrically distributed on two sides of the longitudinal central axis of the area to be excavated along the horizontal direction, and the vertical distance L10 between the pressure relief holes and the arc top of the area to be excavated is 13501mm; the hole spacing between the 2 pressure relief holes is 3000mm; a first row of outer ring auxiliary freezing hole groups DN (92) consisting of 9 outer ring auxiliary freezing holes are longitudinally distributed on edge lines on two sides of the region to be excavated;
Below the area to be excavated: a third row of outer ring freezing hole groups DB (86) formed by 11 outer ring freezing holes, a fourth row of outer ring freezing hole groups DB (87) formed by 10 outer ring freezing holes, a fifth row of outer ring freezing hole groups DB (88) formed by 11 outer ring freezing holes and a sixth row of outer ring freezing hole groups DB (89) formed by 10 outer ring freezing holes are sequentially distributed from top to bottom;
11 outer ring freezing holes in the third row of outer ring freezing hole groups DB (86) are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L15 between a straight line formed by connecting the third row of outer ring freezing hole groups DB (86) and the arc bottom of the region to be excavated is 14808 mm, and the hole spacing between two adjacent outer ring freezing holes is 1197mm;
10 outer ring freezing holes in the fourth row outer ring freezing hole group DB (87) are distributed at equal intervals along the horizontal direction; the vertical distance L16 between a straight line formed by connecting the fourth row of outer ring freezing hole groups DB (87) and the arc bottom of the region to be excavated is 15308mm, and the hole distance between two adjacent outer ring freezing holes is 1189mm;
11 outer ring freezing holes in the fifth row outer ring freezing hole group DB (88) are distributed at equal intervals along the horizontal direction, and one outer ring freezing hole is positioned on the longitudinal central axis of the region to be excavated; the vertical distance L17 between a straight line formed by connecting the outer ring freezing hole groups DB (88) of the fifth row and the arc bottom of the region to be excavated is 15608mm, and the hole spacing between two adjacent outer ring freezing holes is 1197mm;
10 outer ring freezing holes in the sixth row of outer ring freezing hole groups DB (89) are distributed at equal intervals along the horizontal direction; the vertical distance L18 between a straight line formed by connecting the sixth row of outer ring freezing hole groups DB (89) and the arc bottom of the region to be excavated is 15011 mm, and the hole spacing between two adjacent outer ring freezing holes is 1189mm;
a first row of outer ring freezing hole groups DB (84) formed by 8 outer ring freezing holes and a second row of outer ring freezing hole groups DB (85) formed by 10 outer ring freezing holes are distributed on the edge line of the bottom of the area to be excavated from top to bottom; the outer ring freezing holes in the first row outer ring freezing hole group DB (84) are distributed at equal intervals along the horizontal direction, and the vertical distance from the straight line formed by the first row outer ring freezing hole group DB (84) to the straight line formed by the third row outer ring freezing hole group DB (86) is L11; the outer ring freezing holes in the second row outer ring freezing hole group DB (85) are distributed at equal intervals along the horizontal direction, and the vertical distance from the straight line formed by connecting the second row outer ring freezing hole group DB (85) to the straight line formed by connecting the third row outer ring freezing hole group DB (86) is L12.
3. The combined enclosure structure of a freezing wall and a cement reinforcement in the construction of a large-section tunnel according to any one of claims 1-2, wherein the cement reinforcement is a cement grouting area (4), the tunnel face (3) of the large-section tunnel to be excavated is composed of two or more small-section tunnel faces (5) to be excavated which are sequentially arranged from top to bottom, and the cement grouting area (4) is positioned in front of the small-section tunnel faces (5) to be excavated; and the cement grouting area (4) is arranged at intervals of 10m along the excavation direction of the face (5) with the small section to be excavated in the excavation process.
4. An excavation method for a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction by adopting the method for excavating the combined enclosure structure of the freezing wall and the cement reinforcement in large-section tunnel construction, which is characterized by comprising the following steps:
step A: drilling holes according to the design scheme of the cylindrical freezing wall, installing a freezing system, and actively freezing to form a frozen soil curtain, wherein the frozen soil curtain is the cylindrical freezing wall, the cylindrical freezing wall forms a strong freezing region, and the region to be excavated, which is surrounded by the cylindrical freezing wall, is a weak freezing region;
and (B) step (B): after positive freezing is completed, performing primary horizontal grouting in surrounding rock 10m away from the small-section tunnel face (5) to be excavated to form the cement reinforcing body;
step C: after the excavation acceptance check is passed, carrying out sectional horizontal excavation until the primary support of the excavated part is completed, and carrying out next-stage grouting and excavation; sequentially excavating after finishing horizontal grouting every 10m until the primary support of the section to be excavated is completed; grouting reinforcement is carried out after the end is excavated, so that the end reinforcement is completed;
step D: and (3) performing secondary lining construction after water proofing is finished, stopping freezing, plugging all freezing holes inside and outside, and filling, melting, sinking and grouting.
5. The method for excavating a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction according to claim 4, wherein in the step B, a construction area with a large section to be excavated is divided into 4 excavation areas of a first step, a second step, a third step and a fourth step from top to bottom in sequence according to a freezing hole arrangement rule, and each excavation area is excavated horizontally;
Positive freezing is classified into first-stage freezing and second-stage freezing; the first-stage freezing comprises freezing the two excavation areas of the first step and the second step; the second-stage freezing comprises freezing the two excavation areas of the third step and the fourth step; and the second-stage freezing is performed after the second step excavation area is excavated;
the first-stage freezing adopts a cylindrical shape freezing with a straight wall in a shape like a Chinese character 'ri' and a circular arc top bottom, and the frozen first-stage freezing reinforcement area (1) comprises a first upper freezing wall (11), a first bottom middle partition plate freezing wall (12), a first side wall freezing wall (13) and a first middle partition plate freezing wall (14); the first upper freezing wall (11), the first bottom middle partition freezing wall (12), the first side wall freezing wall (13) and the first middle partition freezing wall (14) extend towards a non-excavation area along the small-section tunnel face (5) to be excavated; the second-stage freezing adopts a straight wall arc bottom cylindrical freezing shape like a Chinese character 'ri', and the frozen second-stage freezing reinforcement area (2) comprises a second upper freezing wall (21), a second bottom freezing wall (22), a second side wall freezing wall (23) and a second middle partition plate freezing wall (24); the second upper freezing wall (21) is connected with the first bottom middle partition freezing wall (12) of the first period freezing reinforcement zone (1); the second upper freezing wall (21), the second bottom freezing wall (22), the second side wall freezing wall (23) and the second middle partition plate freezing wall (24) extend towards the trenchless area along the small section face (5) to be excavated.
6. The method for excavating a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction according to claim 5, wherein the step C is divided into the following steps:
digging a first step in the step (C-11): sequentially carrying out sectional horizontal excavation after horizontal grouting for every 10m, and supporting along with excavation until the primary support of the first step is completed; then carrying out horizontal grouting reinforcement after the first step is excavated to the end head so as to finish the end reinforcement of the first step; after the first step excavation is completed completely: installing a first middle partition plate in the construction of a first step, and performing grouting end-capping reinforcement on a to-be-excavated area of a second step by utilizing a vertical grouting hole in the construction of an excavated space of the first step;
and (3) excavating a second step in the step (C-12): excavating a second step by adopting an excavating method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the second step; after the excavation of the second step is completed, constructing and installing a first bottom middle partition plate on the second step, and performing grouting end-capping reinforcement on a third step to-be-excavated area by utilizing a vertical grouting hole constructed in an excavation space of the second step;
And (3) excavating a third step: after the second step is excavated, performing second-stage freezing, and after the second-stage freezing is finished, excavating the third step according to the excavation construction method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the third step; after the excavation of the third step is completed, constructing and installing a second middle partition plate on the third step, and performing grouting end-capping reinforcement on a fourth step to-be-excavated area by utilizing a vertical grouting hole in the excavation space of the third step;
excavating a fourth step in the step (C-14): excavating a fourth step by adopting the excavating method of the first step; and (3) carrying out horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the fourth step.
7. The method for excavating a combined enclosure structure of a freezing wall and a cement reinforcement in large-section tunnel construction according to claim 4, wherein in the step B, a construction area with a large section to be excavated is divided into 3 excavation areas of a first step, a second step and a third step from top to bottom in sequence according to a freezing hole arrangement rule, and each excavation area is excavated horizontally;
After positive freezing is completed, the formed frozen soil curtain is a 'mesh' -shaped arc top-bottom type freezing wall, and the arc top-bottom type freezing wall encloses a third freezing reinforcement area (30); the third freezing and reinforcing region (30) comprises a third upper freezing wall (301), a third bottom freezing wall (302), a third side wall freezing wall (303), a third middle partition plate freezing wall A (304) and a third middle partition plate freezing wall B (305); the third upper freezing wall (301), the third bottom freezing wall (302), the third side wall freezing wall (303), the third middle partition plate freezing wall A (304) and the third middle partition plate freezing wall B (305) all extend to a non-excavation area along a small-section tunnel face (5) to be excavated;
step C can be divided into the following steps:
digging a first step in the step (C-21): sequentially carrying out sectional horizontal excavation after horizontal grouting for every 10m, and supporting along with excavation until the primary support of the first step is completed; then carrying out horizontal grouting reinforcement after the first step is excavated to the end head so as to finish the end reinforcement of the first step; after the first step excavation is completed completely: installing a third middle partition plate A in the construction of the first step, and performing grouting end-capping reinforcement on a to-be-excavated area of the second step by utilizing a vertical grouting hole in the construction of an excavated space of the first step;
And (3) excavating a second step in the step (C-22): excavating a second step by adopting an excavating method of the first step; performing horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the second step; after the excavation of the second step is completed, a third middle partition board B is installed on the second step in a construction mode, and grouting end-sealing reinforcement is carried out on a third step area to be excavated by utilizing a vertical grouting hole in the construction mode of an excavation space of the second step;
and (3) excavating a third step in the step (C-23): excavating a third step by adopting the excavating method of the first step; and (3) carrying out horizontal grouting reinforcement after excavating to the end head so as to finish the end reinforcement of the third step.
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| CN115019618B (en) * | 2022-04-19 | 2023-02-28 | 中国海洋大学 | High-temperature water-rich weak stratum tunnel curtain grouting excavation model test device and method |
| CN114856578A (en) * | 2022-04-20 | 2022-08-05 | 中铁一局集团有限公司 | Freezing and in-hole grouting improved combined bearing stratum reinforcing scheme |
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