CN114109436A - Large-span underground excavation construction method for subway station - Google Patents
Large-span underground excavation construction method for subway station Download PDFInfo
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- CN114109436A CN114109436A CN202111459239.1A CN202111459239A CN114109436A CN 114109436 A CN114109436 A CN 114109436A CN 202111459239 A CN202111459239 A CN 202111459239A CN 114109436 A CN114109436 A CN 114109436A
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- 238000009412 basement excavation Methods 0.000 title claims abstract description 52
- 238000010276 construction Methods 0.000 title claims abstract description 45
- 239000011435 rock Substances 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 19
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 7
- 239000010959 steel Substances 0.000 claims abstract description 7
- 238000004873 anchoring Methods 0.000 claims description 19
- 239000004567 concrete Substances 0.000 claims description 15
- 239000003795 chemical substances by application Substances 0.000 claims description 12
- 238000005553 drilling Methods 0.000 claims description 10
- 238000005507 spraying Methods 0.000 claims description 9
- 230000008093 supporting effect Effects 0.000 claims description 7
- 230000003014 reinforcing effect Effects 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 4
- 230000005641 tunneling Effects 0.000 claims description 3
- 230000008901 benefit Effects 0.000 abstract description 6
- 230000008569 process Effects 0.000 abstract description 5
- 239000011378 shotcrete Substances 0.000 abstract description 5
- 238000005260 corrosion Methods 0.000 abstract description 3
- 230000007797 corrosion Effects 0.000 abstract description 3
- 238000005422 blasting Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002360 explosive Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000004568 cement Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
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- 229920000742 Cotton Polymers 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
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- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
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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
- E21D9/14—Layout of tunnels or galleries; Constructional features of tunnels or galleries, not otherwise provided for, e.g. portals, day-light attenuation at tunnel openings
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
- E21D20/02—Setting anchoring-bolts with provisions for grouting
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/008—Anchoring or tensioning means
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/0086—Bearing plates
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/0093—Accessories
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- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Architecture (AREA)
- Environmental & Geological Engineering (AREA)
- Civil Engineering (AREA)
- Lining And Supports For Tunnels (AREA)
Abstract
The invention relates to the technical field of constructional engineering, and provides a large-span underground excavation construction method for a subway station. According to the invention, the excavation surface is subjected to advanced pre-support before excavation, so that the actual construction risk can be reduced, and the smooth proceeding of the construction process is ensured; meanwhile, the NPR prestressed anchor rod with the advantages of high constant resistance, large elongation, corrosion resistance and the like is applied to primary support, and on the basis of reasonably controlling the parameters of the NPR prestressed anchor rod and detecting the stress condition of the anchor rod, the NPR prestressed anchor rod, the advanced small guide pipe, the sprayed concrete, the grid steel frame, the foot locking anchor rod and the like form a combined support system with better stability, so that the mechanical property of surrounding rock is improved, the bearing capacity of the surrounding rock is fully exerted, and the stability of a cavern is ensured.
Description
Technical Field
The invention relates to the technical field of constructional engineering, in particular to a large-span underground excavation construction method for a subway station.
Background
The arch cover method is a method developed in recent years and suitable for shallow-buried large-span underground excavation of a soft upper stratum and a hard lower stratum, and is mainly used for underground excavation of subway stations with large spans to replace a traditional middle hole method, a double-side-wall pit guiding method and the like. The early method is a two-lining arch cover method, namely, the preliminary bracing of the arch part and the secondary lining are completed, then the lower part construction is carried out, and the preliminary bracing arch cover method is gradually explored in recent years, namely, the preliminary bracing of the arch part is completed, namely, the lower part construction is carried out, and the preliminary bracing is mostly two layers, namely, a double-layer steel frame and a double-layer sprayed concrete.
The surrounding rock of a certain subway station belongs to IV-grade surrounding rock, is soft at the upper part and hard at the lower part, is broken and soft at the upper part, and is suitable for construction by an arch cover method, but the construction period is long and the cost is high according to a two-lining arch cover and a double-layer primary support arch cover, while the construction safety is difficult to ensure and the construction risk is higher by adopting the traditional one-layer primary support.
Disclosure of Invention
The invention aims to provide a large-span underground excavation construction method for a subway station, which can effectively reduce actual construction risks and ensure the smooth progress of a construction process.
The embodiment of the invention is realized by the following technical scheme:
a large-span underground excavation construction method for a subway station comprises the following steps:
s1, performing advanced pre-support on surrounding rocks along a tunneling direction on an excavation face; the advanced pre-support application comprises the following steps:
s11, determining the placing position of the advanced small guide pipe on the excavation surface according to design requirements and drilling;
s12, spraying concrete on the excavation surface to seal the excavation surface;
s13, installing the advanced small guide pipes, and sequentially grouting the advanced small guide pipes;
s2, after the advanced pre-support construction is finished, excavating an arch part, and constructing a primary support;
and S3, after the arch part is communicated, excavating a lower section.
Optionally, in step S2, the preliminary bracing construction includes:
s21, primarily spraying concrete on the surrounding rock surface;
s22, sequentially constructing an NPR prestressed anchor rod, erecting a steel grating and constructing a foot locking anchor rod;
and S23, re-spraying concrete.
Further, in step S21, the applying of the NPR prestressed anchor rod includes:
s211, drilling a hole in the surrounding rock surface according to design requirements, and then cleaning and checking the hole;
s212, placing an anchoring agent in the hole; the front end of the NPR prestressed anchor rod extends into the hole, and the rear end of the NPR prestressed anchor rod is connected with a stirrer; stirring the anchoring agent by using an NPR prestressed anchor rod;
s213, after a certain time, detaching a stirrer at the rear end of the NPR prestressed anchor rod, and installing an anchor backing plate, a clamping piece and an anchorage at the rear end of the NPR prestressed anchor rod to finish the construction of the NPR prestressed anchor rod;
s214, tensioning the NPR prestressed anchor rod.
Optionally, in step S2, the arch part is excavated by an up-down step method, a first pilot tunnel is excavated first, and preliminary support is applied after excavation is completed; and then excavating No. two pilot tunnels by adopting a middle pull groove, excavating No. three pilot tunnels and No. four pilot tunnels in a staggered manner after the excavation is finished, and constructing the remaining primary support of the arch part.
Furthermore, after the arch part is excavated and is applied with primary support, an arch foot reinforcing anchor rod is applied to the arch foot, the arch foot reinforcing anchor rod is tensioned and locked, and then concrete is sprayed again to the designed arch foot thickness.
The technical scheme of the embodiment of the invention at least has the following advantages and beneficial effects:
1. according to the invention, the advance pre-support is applied to the excavation surface before excavation, so that the actual construction risk can be reduced, and the smooth proceeding of the construction process can be ensured.
2. The NPR prestressed anchor rod with the advantages of high constant resistance, large elongation, corrosion resistance and the like is applied to primary support, and on the basis of reasonably controlling the parameters of the NPR prestressed anchor rod and detecting the stress condition of the anchor rod, the NPR prestressed anchor rod, the advanced small guide pipe, the sprayed concrete, the grid steel frame, the foot locking anchor rod and the like form a combined support system with better stability, so that the mechanical property of surrounding rock is improved, the bearing capacity of the surrounding rock is fully exerted, and the stability of a cavern is ensured.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a construction flow chart of underground excavation of a large-span subway station provided by an embodiment of the invention;
fig. 2 is a schematic structural view of a large-span underground station underground excavation surface provided by the embodiment of the invention.
Icon: 1-advanced small guide pipe, 2-NPR prestressed anchor rod and 3-arch foot reinforced anchor rod.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually placed when the product of this application is used, the description is merely for convenience and simplicity of description, and it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
Examples
Referring to fig. 1 and 2, the embodiment provides a large-span underground excavation construction method for a subway station, which includes applying advanced pre-support, arch excavation, arch preliminary support and lower section excavation to surrounding rocks on an excavation surface. The method comprises the following specific steps:
s1, performing advanced pre-support on surrounding rocks along the tunneling direction on an excavation face. The advanced pre-support application comprises the following steps:
s11, determining the placing position of the advanced small guide pipe 1 on the excavation surface according to design requirements, and drilling holes so as to install the advanced small guide pipe 1. Preferably, the placing positions of the advanced small guide pipes 1 are sequentially measured along the excavation contour line, and holes for placing the advanced small guide pipes 1 are drilled by an air drill.
In the embodiment, the small advanced guide pipe 1 is a hot-rolled seamless steel pipe with phi 42-4 mm, the front end of the small advanced guide pipe 1 is processed into a cone shape, a hooping with phi 6mm is welded at the rear end of the small advanced guide pipe 1, grouting holes are drilled on the pipe wall of the small advanced guide pipe 1 at a position 1.05m away from the rear end of the small advanced guide pipe 1, the grouting holes are arranged at intervals of 150-200mm along the pipe wall and in a quincunx shape, the aperture of the grouting holes is 6-8mm, and the hole positions are arranged at 90 degrees, so that the grouting construction quality is ensured.
S12, before grouting the advanced small guide pipe 1, spraying concrete of 5-10cm on the excavation surface to seal the excavation surface, and preventing the phenomenon of slurry leakage when grouting the advanced small guide pipe 1.
S13, sequentially installing the advanced small guide pipe 1 into the drilled hole, installing a grout stop plug at the rear end of the advanced small guide pipe 1 after the advanced small guide pipe 1 is installed and communicating with an external grouting pipe, and sequentially grouting the advanced small guide pipe 1.
During grouting, the advanced small pipes 1 are sequentially grouted from two sides of the excavation face from bottom to top, namely the advanced small pipes 1 are sequentially grouted from two sides of the excavation face, the advanced small pipes 1 are sequentially grouted from bottom to top, so that the construction efficiency is improved, the advanced small pipes 1 on the lower portion are sequentially grouted, the supporting effect of advanced pre-supporting can be further improved, and the stability of the excavation face is improved.
In actual grouting, the grouting pressure of the single advanced small pipe 1 is determined according to the compactness of the rock stratum, the grouting pressure of the embodiment is 0.4-1MPa, and the grouting slurry adopts sulfate cement with the cement mark of P.O425. Meanwhile, the grouting amount Q of each advanced small catheter 1 is calculated using the following formula:
Q＝πR2*L*n*K；
wherein R is the slurry diffusion radius; l is the length of the advanced small catheter 1; n is the porosity of the rock mass; k is filling coefficient, and is 0.3-0.5. In actual implementation, the value of K can be selected according to different geological conditions. The construction quality of the advanced small catheter 1 is further improved by reasonably controlling the grouting pressure and the grouting amount of the advanced small catheter 1, so that the advanced small catheter 1 is utilized to achieve a good pre-supporting effect.
And S2, after the advanced pre-supporting construction is finished, firstly digging an arch and constructing primary support for the arch.
Specifically, when the arch part is excavated, a reasonable excavation mode can be selected according to various factors such as buried depth, stratum lithology and geological conditions, for example, an annular pilot tunnel method or an upper and lower step method is adopted to excavate the arch part. Preferably, the arch part is excavated by adopting an up-and-down bench method in the embodiment, so that the grid nodes are prevented from being suspended in the air during construction, and the safety risk of lower excavation is reduced.
The arch part is divided into a guide tunnel I and a guide tunnel II, the guide tunnel I is excavated firstly during excavation, and corresponding primary support is constructed after the guide tunnel I is excavated; and then excavating a pilot tunnel II by adopting a middle pull groove, excavating pilot tunnels III and IV in a staggered way after the pilot tunnel II is excavated, wherein the longitudinal interval of the pilot tunnels is not less than 15m, and constructing the remaining primary support of the arch part to finish the excavation and the support of the arch part.
Specifically, the construction of the primary support comprises the following steps:
s21, primarily spraying concrete on the surrounding rock surface to form a first concrete support. It should be noted that the thickness of the primary sprayed concrete should be determined according to the specific situation of the surrounding rock, and when the integrity of the surrounding rock is good, the primary sprayed concrete should be fiber concrete with the thickness of 6-8 cm; and when the completion of the surrounding rock is poor, concrete with the thickness of 3-5cm is sprayed initially.
And S22, sequentially constructing the NPR prestressed anchor rods 2, erecting a steel grating and constructing a foot locking anchor rod to ensure good supporting effect of primary support. It should be noted that by adopting the NPR prestressed anchor rods 2 and cooperating with the advanced pre-support before excavation, a more stable combined support system can be formed, and the stability of the excavated cavern surrounding rock is ensured, so that the construction quality is further improved, and the construction risk is reduced.
And S23, finally, spraying concrete again to the designed thickness to finish the construction of the primary support.
The NPR prestressed anchor rod 2 is formed by reconstructing microcosmic NPR crystals (2-5 nm) and PR crystals, the yield strength of the anchor rod is 600-1110MPa, the elongation is 35-70%, and the anchor rod has the advantages of high constant resistance, large elongation, uniformity, large deformation, rockburst resistance, impact resistance, no magnetism, magnetization resistance, corrosion resistance and the like. The NPR prestressed anchor rod 2 is applied to primary support, and the stability of surrounding rocks in the construction process can be further improved by reasonably controlling the parameters (such as the diameter of the anchor rod, the length of an anchoring section, the size of an anchor backing plate and the like) of the NPR prestressed anchor rod.
The NPR prestressed anchor rod 2 comprises the following components:
s211, drilling an installation hole of the NPR prestressed anchor rod 2 on the surrounding rock surface by adopting an excavation-modification rock drill according to design requirements, and drilling the hole vertical to the surrounding rock so as to ensure the installation of an anchor backing plate; meanwhile, the allowable angle deviation of the preset direction of the drilling hole and the anchor rod is 1-3 degrees, the deviation of hole sites is less than 5cm, and the hole depth and the hole diameter of the drilling hole both meet the design requirements. And cleaning the hole after the drilling is finished so as to remove accumulated water or rock powder in the hole, and inspecting the drilled hole so as to ensure that the drilled hole meets the design requirement.
In this embodiment, the diameter of the NPR prestressed anchor rod 2 is phi 18mm, wherein the length of the anchoring section is greater than or equal to one third of the length of the anchor rod; meanwhile, the anchor backing plate is 150 × 10mm in size, so that the anchoring effect of the NPR prestressed anchor rod 2 is ensured to meet the design and construction requirements.
S212, subsequently, checking the quality of the anchoring agent, and putting the anchoring agent into the drill hole; cleaning impurities such as water and rock debris in the anchoring section of the NPR prestressed anchor rod 2 by using cotton fibers, bonding and positioning the explosive cartridge and the anchoring section of the anchor rod by using plastic box sealing glue, wherein the front end of the NPR prestressed anchor rod 2 extends into the hole, and the rear end of the NPR prestressed anchor rod is connected with a stirrer; the NPR prestressed anchor rod 2 is used for stirring the anchoring agent, the stirring time is controlled to be 20-30s, and the stirring process cannot be stopped so as to ensure the construction quality; and after the stirring is stopped, continuously keeping the thrust of the bolting machine for about 3min, and then removing the bolting machine.
And after S213.10min, detaching the stirrer at the rear end of the NPR prestressed anchor rod 2, and installing an anchor backing plate, a clamping piece and an anchorage device (namely an anchor head) at the rear end of the NPR prestressed anchor rod 2 to enable the anchor backing plate to be tightly attached to the surface of the surrounding rock, so that the construction of the NPR prestressed anchor rod 2 is completed.
It should be noted that, when the water accumulation in the bore hole for installing the NPR prestressed anchor 2 is large, the anchor agent should be an inorganic anchor agent to improve the anchoring effect. Preferably, the anchoring agent of the embodiment adopts a medium-speed resin anchor rod anchoring agent with the diameter of 25 mm.
S214, after the NPR prestressed anchor rod 2 is applied (namely after the anchoring agent is stirred for 10-15 min), the NPR prestressed anchor rod 2 is tensioned to ensure the anchoring effect. During tensioning, pre-tensioning is carried out, and the tensioning force at the moment is 10-20% of the design tensioning force; and then, the NPR prestressed anchor rod 2 is tensioned in a mode of gradually applying tension in stages, each tensioning is preferably divided into 5-6 stages, the load-holding stabilization time of each stage is 5 minutes except that the first stage of tensioning needs 30 minutes for stabilization, and the load cannot be applied to the locking load once. The tension is increased in a stepwise manner, specifically in a manner of 0.2P → 0.25P → 0.5P → 0.75P → 1.0P → 1.10P, where P is the design tension value.
Meanwhile, after the NPR prestressed anchor rod 2 is tensioned to a set maximum tensioning load value, the load should be kept stable for 10-15min, whether prestress loss exists is judged by observing the pressure value and the elongation change of an oil pump, if so, tensioning compensation is carried out in time, and locking operation is carried out after unloading. After tensioning is finished, the NPR prestressed anchor rods 2 are subjected to uplift test detection, the requirement that the average value of the uplift force of the same batch of anchor rods is not less than the anchoring force required by the design is met, the minimum value of the uplift force of the same batch of anchor rods is not less than 90% of the anchoring force required by the design, the number of the detection is not less than 3% of the total number of the anchor rods, and 3 anchor rods are taken out when the number of the detection is less than 100.
It should be noted that, in order to further improve the stability of the arch, after the arch is excavated and preliminary supporting is performed, the arch foot reinforcing anchor rods 3 are performed on the arch feet, the arch foot reinforcing anchor rods 3 are tensioned and locked, and then concrete is sprayed again to the designed arch foot thickness.
And S3, after the arch part is communicated, excavating a lower section by adopting a middle pull groove. Wherein, the lower section is divided into guide holes with the numbers from five to red, wherein, the guide hole with the number of sixty includes 6a and 6b, the guide hole with the number of eight includes 8a and 8b, and the guide hole with the number of nine includes 9a and 9 b. During excavation, excavating according to the order of guide tunnel with fifth to third cavities; meanwhile, when excavating guide holes No. sixteenth, No. sixteenth and No. ninth, the excavation is also carried out in a staggered excavation mode. When excavating, the distance between adjacent steps should be not less than 5 m.
It should be noted that, when actually excavating an arch or a lower section, the main body should be excavated by adopting a smooth blasting mode, peripheral holes are distributed along an excavation contour line, explosives with small dosage are filled in the peripheral holes, the explosive filled in the peripheral holes is loaded in an uncoupled mode, and then the blasting is completed by initiating at the same time. Through adopting smooth blasting, can blast and form more smooth country rock face to do benefit to further construction operation.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A large-span underground excavation construction method for a subway station is characterized by comprising the following steps:
s1, performing advanced pre-support on surrounding rocks along a tunneling direction on an excavation face; the advanced pre-support application comprises the following steps:
s11, determining the placing position of the advanced small guide pipe on the excavation surface according to design requirements and drilling;
s12, spraying concrete on the excavation surface to seal the excavation surface;
s13, installing the advanced small guide pipes, and sequentially grouting the advanced small guide pipes;
s2, after the advanced pre-support construction is finished, excavating an arch part, and constructing a primary support;
and S3, after the arch part is communicated, excavating a lower section.
2. The underground excavation construction method for the large-span subway station as claimed in claim 1, wherein in step S2, the preliminary bracing construction comprises:
s21, primarily spraying concrete on the surrounding rock surface;
s22, sequentially constructing an NPR prestressed anchor rod, erecting a steel grating and constructing a foot locking anchor rod;
and S23, re-spraying concrete.
3. The underground excavation construction method for the large-span subway station as claimed in claim 2, wherein in step S21, the applying of the NPR prestressed anchor rods comprises:
s211, drilling a hole in the surrounding rock surface according to design requirements, and then cleaning and checking the hole;
s212, placing an anchoring agent in the hole; the front end of the NPR prestressed anchor rod extends into the hole, and the rear end of the NPR prestressed anchor rod is connected with a stirrer; stirring the anchoring agent by using an NPR prestressed anchor rod;
s213, after a certain time, detaching a stirrer at the rear end of the NPR prestressed anchor rod, and installing an anchor backing plate, a clamping piece and an anchorage at the rear end of the NPR prestressed anchor rod to finish the construction of the NPR prestressed anchor rod;
s214, tensioning the NPR prestressed anchor rod.
4. The underground excavation construction method for the large-span subway station as claimed in claim 1, wherein in step S2, the arch portion is excavated by an up-down step method, firstly, a first pilot tunnel is excavated, and after the excavation is completed, preliminary bracing is performed; and then excavating No. two pilot tunnels by adopting a middle pull groove, excavating No. three pilot tunnels and No. four pilot tunnels in a staggered manner after the excavation is finished, and constructing the remaining primary support of the arch part.
5. The underground excavation construction method for the large-span subway station as claimed in claim 4, wherein after the arch portion is excavated and preliminary supporting is applied, arch foot reinforcing anchor rods are applied to the arch feet, the arch foot reinforcing anchor rods are tensioned and locked, and then concrete is sprayed again to the designed thickness of the arch feet.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114382520A (en) * | 2022-03-25 | 2022-04-22 | 中国矿业大学(北京) | NPR anchor rod active supporting method suitable for hard rock tunnel |
| CN116641724A (en) * | 2023-07-27 | 2023-08-25 | 中国矿业大学(北京) | Cooperative control method for high-prestress constant-resistance anchor rod and anchor cable of deep-buried soft rock roadway |
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| CN104653206A (en) * | 2014-12-15 | 2015-05-27 | 魏兴民 | Prestress full-length anchoring anchor rope construction method based on common anchor rope construction |
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