CN117967323B - Reinforcing ring structure at hydraulic tunnel fork-to-branch hole interface and roof-picking construction method - Google Patents
Reinforcing ring structure at hydraulic tunnel fork-to-branch hole interface and roof-picking construction method Download PDFInfo
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- 238000010276 construction Methods 0.000 title claims abstract description 71
- 230000003014 reinforcing effect Effects 0.000 title claims abstract description 65
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 207
- 239000010959 steel Substances 0.000 claims abstract description 207
- 230000007704 transition Effects 0.000 claims abstract description 10
- 238000009412 basement excavation Methods 0.000 claims description 33
- 238000000034 method Methods 0.000 claims description 14
- 239000004567 concrete Substances 0.000 claims description 12
- 238000005507 spraying Methods 0.000 claims description 10
- 239000002689 soil Substances 0.000 claims description 8
- 238000009434 installation Methods 0.000 claims description 7
- 239000004568 cement Substances 0.000 claims description 3
- 239000002360 explosive Substances 0.000 claims description 3
- 239000004570 mortar (masonry) Substances 0.000 claims description 3
- 239000011378 shotcrete Substances 0.000 claims description 3
- 238000003466 welding Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 abstract description 6
- 239000011435 rock Substances 0.000 description 11
- 230000009471 action Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000003351 stiffener Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000009933 burial Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
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- 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
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Abstract
The invention discloses a reinforcing ring structure at a hydraulic tunnel fork transfer branch hole interface and a roof-picking construction method, which belong to the technical field of hydraulic tunnel fork transfer branch holes and comprise the following steps: constructing a junction transition section of the fork hole and the branch hole; constructing a fork reinforcing ring at the intersection section of the fork and the branch hole; the fork hole enters a branch hole and is subjected to roof picking construction; and (5) primary support of the support hole. The invention provides a novel form of a reinforcing ring structure (an inner double-spliced 4-truss steel arch frame and an outer double-spliced 2-truss portal steel frame) in the top-picking range, and simultaneously, pull rods are additionally arranged on two sides of the top of the arch frame; the stress conversion of the main beam and the secondary beam of the cross section supporting structure is simplified and analyzed, and the stress condition of the supporting structure is analyzed by adopting a two-dimensional calculation model in combination with the standard, so that the stress is taken as the design basis of the reinforcing ring steel frame at the intersection position, and the stability of the stress of the reinforcing ring steel frame is ensured. Aiming at the stress characteristics of the reinforcing ring steel frame, the invention provides corresponding construction measures for ensuring the overall anti-overturning stability of the reinforcing ring steel frame outside the plane, and improves the overall stability of the support system.
Description
Technical Field
The invention relates to the technical field of hydraulic tunnel turnout and turnout junction, in particular to a reinforcing ring structure at a hydraulic tunnel turnout and turnout junction interface and a top-picking construction method.
Background
The construction of hydraulic tunnels is limited by the complicated underground environment of mountain areas, and the conditions of open excavation or underground shaft excavation are often not met, so that a construction scheme of jacking and entering holes and excavating from positive holes to two ends is generally adopted for excavating inclined shafts (fork holes and branch holes) in the middle of the tunnel, so that the working face is increased, and the construction period requirement is met.
The supporting structure and the construction procedure of the crossing section of the branch hole entering from the middle of the tunnel are complex and changeable, surrounding rock is subjected to multiple disturbance, the stress distribution of the surrounding rock and the deformation rule of the supporting structure are complex, the phenomenon of stress concentration is easy to occur, and the surrounding rock is not beneficial to stability. In addition, because the design of the hydraulic tunnel often cannot be expressed in detail at the top-picking position, the design and calculation of the interface position reinforcing ring steel frame need to be further defined in the construction scheme. Therefore, the conversion construction of the two is often an important point and a difficult point of engineering. Meanwhile, the mechanical behavior of the intersection steering and roof-lifting construction needs to be ascertained so as to ensure the safety of tunnel construction.
Based on the structure, the invention designs a reinforcing ring structure at the junction of the fork and the branch of the hydraulic tunnel and a roof-picking construction method to solve the problems.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a reinforcing ring structure at a turning branch hole interface of a hydraulic tunnel fork hole and a roof-picking construction method.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
A hydraulic tunnel fork-hole transfer support-hole top-picking construction method comprises the following steps:
1. Construction of junction transition section of fork hole and branch hole
Excavating a junction transition section of the fork hole and the branch hole by adopting a step method, adopting a special-shaped steel frame as a primary support steel frame, erecting the special-shaped steel frame away from a normal line, gradually adjusting the direction of the steel frame and the arch height of the steel frame, and lengthening the steel arch A;
2. construction of fork hole reinforcing ring at intersection section of fork hole and branch hole
After the branch is constructed to the branch hole digging contour line, an advanced support and reinforcing ring structure is applied at the intersection; the reinforcing ring structure consists of a steel arch and a portal steel frame; the inner side of the reinforcing ring structure is provided with 4 steel arches B which are spliced together, the outer side of the reinforcing ring structure is provided with 2 door-shaped steel frames which are spliced together, and the door-shaped steel frames are welded together with the steel arches B in sections;
3. top-picking construction for branch hole entering branch hole
Backfilling core soil at the intersection of a construction fork hole and a support hole, then entering the support hole in a small pilot hole mode, adopting a portal steel frame for supporting in the support hole, gradually lifting the top elevation of the portal steel frame of the support hole along with the deep excavation, reaching the top elevation of the support hole at the central line of the support hole, wherein the excavation height is larger than the excavation outline of the support hole, and the reserved deformation and temporary supporting thickness are considered in construction;
the vertical branch tunnel is excavated, the excavation width of the tunnel is 4.9m, the excavation height reaches 0.6m above the excavation contour line of the tunnel main tunnel, and the step on the tunnel is excavated in a mode of reserving core soil; the early excavation of the roadway adopts a fold line to be picked up so as to be connected with the arch part of the fork hole section in sequence, and the arch part of the inclined roadway adopts a rectangle after a certain distance is excavated so as to be beneficial to primary support compaction of the branch hole;
4. initial support for supporting tunnel
Furthermore, 8 steel frames are arranged for each steel frame of the fork42 Lock foot anchor pipe, adopt/> -between the adjacent steelframe25 Longitudinal steel bars are connected, and the circumferential spacing of the connecting steel bars is 1m
Further, the fork arch part is installed within 120 DEG42 Leading small catheter, arch part adopting/>25 Explosive roll anchor rod, side wall adopts/>25 Mortar anchor rods; c25 concrete spraying protection is adopted for arch walls and inverted arches
Furthermore, the steel arch A of the transition section of the fork hole adopts a labor 18 steel arch, and the steel arch is in fan-shaped arrangement
Furthermore, the portal steel frame consists of a beam and an upright post, the gap between the beam and the steel arch B is vertically supported and connected, and the sprayed concrete at the gap is backfilled compactly
Furthermore, 8 system anchor rods and 4 anchor rods are additionally arranged on each side of the door-shaped steel frame42 Lock foot anchor pipe
Further, the door-shaped steel frame segments are welded with the steel arch B, and the concrete steps comprise:
The vertical supports are fixedly connected with the arc-shaped steel arch B, the distance between every two adjacent vertical supports is 0.5m, the cross beam is fixedly connected with the vertical supports by adopting a multiple lengthening method, and the vertical supports are fixedly connected with the steel arch B by welding; synchronous carrying out of girder sectional lengthening installation and longitudinal upper step excavation of supporting tunnel
Further, after the supporting hole roof-picking construction is completed, carrying out supporting hole primary support construction on the inner side of an excavated section according to supporting hole primary support parameters, wherein one end of a supporting hole primary support steel frame is supported on the upper part of a cross beam in the range of an intersection, the other end of the supporting hole primary support steel frame is supported on a steel plate, foot locking anchor pipes are additionally arranged at the joint parts and arch feet of the supporting hole primary support steel frame, cement paste is injected, and the foot locking anchor pipes are firmly welded with the supporting hole primary support steel frame; measuring pay-off marks on the side wall of the pilot tunnel to mark a pilot tunnel digging contour line after the primary support of the step on the pilot tunnel in the pilot tunnel is completed, removing the temporary support on one side of the small pilot tunnel steel frame, performing primary support in the pilot tunnel direction, digging an upper arc pilot pit, digging forward, spraying concrete to seal the tunnel face, and suspending the digging in the direction; turning around and removing temporary support on the other side of the small pilot tunnel steel frame, performing primary support in the direction of the pilot tunnel, excavating an upper arc pilot tunnel, excavating forwards, spraying concrete to seal the tunnel face, and suspending excavation in the direction; when the arc pilot pit of the upper step is dug, the reserved deformation of the arch crown of the branch hole is gradually reduced; the inverted arch steel frame of the branch hole in the width range of the branch hole is connected with the bottom transverse strut steel frame of the last reinforcing ring of the branch hole, so that the primary support steel frame of the branch hole in the range of the intersection is looped as soon as possible
A reinforcing ring structure at the junction of a hydraulic tunnel fork and a branch hole, which is used for the hydraulic tunnel fork and branch hole top-picking construction method, comprises a reinforcing ring structure, wherein the reinforcing ring structure is a steel arch frame and a portal steel frame; the inner side of the reinforcing ring structure is a double-spliced steel arch B with 4I 22B, the outer side of the reinforcing ring structure is a double-spliced door-shaped steel frame with 2I 22B, and the door-shaped steel frame cross beam sections are welded with the steel arch B.
Advantageous effects
1. Aiming at the characteristic of poor stability of surrounding rock under V-level surrounding rock, the invention provides a top-picking construction scheme of a hydraulic tunnel fork turning support hole, which can greatly improve construction efficiency, ensure construction safety and provide reference for similar engineering.
2. The method simplifies and analyzes the stress conversion of the main beam and the secondary beam of the cross section supporting structure, combines the standard and adopts a two-dimensional calculation model to analyze the stress condition of the supporting structure, and uses the stress condition as the design basis of the reinforcing ring steel frame at the intersection position, thereby ensuring the stress stability of the reinforcing ring steel frame.
3. The invention provides a novel reinforcing ring structure form (an inner double-spliced 4-truss steel arch frame and an outer double-spliced 2-truss portal steel frame) in the top-picking range, meanwhile, pull rods are additionally arranged on two sides of the top of the arch frame, and the structural form can be found to be more reasonable in stress by combining calculation and analysis, so that the excessive concentration of stress on the arch frame foot is avoided, and the stress stability of the reinforcing ring steel frame is improved.
4. The invention combines the difficulty of site construction, and provides a method for installing the portal steel frame beam in a segmented way, which is convenient for site installation and construction.
5. Aiming at the stress characteristics of the reinforcing ring steel frame, the invention provides corresponding construction measures for ensuring the overall anti-overturning stability of the reinforcing ring steel frame outside the plane, and improves the overall stability of the support system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 is a general plan layout diagram of a hydraulic tunnel fork-to-branch tunnel construction of the present invention;
FIG. 2 is a plan view of an arrangement of steel arches at the top of a hydraulic tunnel fork transfer branch in an embodiment of the invention;
FIG. 3 is a longitudinal section view I of the hydraulic tunnel fork-turning branch tunnel construction of the present invention;
FIG. 4 is a second longitudinal section view of the hydraulic tunnel fork-to-branch tunnel construction of the present invention;
FIG. 5 is a cross-sectional view of the junction of the branch hole and the branch hole of the hydraulic tunnel according to the present invention;
FIG. 6 is a view of a steel arch and a portal frame;
FIG. 7 is a top beam mounting step one at the stiffener ring;
FIG. 8 is a top beam mounting step two at the stiffener ring;
FIG. 9 is a top beam mounting step three at the stiffener ring;
FIG. 10 is a view of a portal frame inside a pilot tunnel.
Reference numerals in the drawings represent respectively:
11. A steel arch A; 12. a fork hole; 13. steel arch and portal frame; 131. a steel arch B; 132. a portal steel frame; 1321. a cross beam; 1322. a column; 1323. a vertical support; 21. a tunnel face; 22. a support hole; 23. locking the pin anchor pipe; 24. a primary support steel frame of the support hole; 25. small pilot tunnel steel frame.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is further described below with reference to examples.
Example 1
Referring to fig. 1-10 of the specification, the hydraulic tunnel fork turning support roof-picking construction method comprises the following steps:
1. Junction transition section construction of fork hole 12 and branch hole 22
The junction transition section of the fork hole 12 and the branch hole 22 is excavated by adopting a step method, the primary support steel frame adopts a special-shaped steel frame, the special-shaped steel frame is erected from the normal line, the direction and the arch height of the special-shaped steel frame are gradually adjusted, the steel arch A11 is gradually lengthened, and 8 branch holes 12 are arranged at each frame42 Foot locking anchor pipe 23, and/>, is adopted between steel arches A1125 Longitudinal steel bars are connected, and the circumferential spacing of the connecting steel bars is 1m; arch 120 ° range installation/>42 Leading small guide pipes, and encrypting the circumferential spacing and the row spacing according to actual conditions; arch part adopts/>25 Explosive roll anchor rod, side wall adopts/>25 Mortar anchor rods; c25 concrete is adopted for spraying and protecting the arch wall and the inverted arch;
Preferably, the fork hole transition section steel arch A11 adopts a labor 18 steel arch, and the steel arch A11 is arranged in a fan shape;
2. construction of reinforcing ring of fork hole 12 at intersection section of fork hole 12 and branch hole 22
After the profile line is excavated from the construction fork hole 12 to the branch hole 22, an advanced support and reinforcing ring structure is applied at the intersection;
The reinforcing ring structure is a steel arch frame and a portal steel frame 13; the steel arch and the portal steel frame 13 comprise a steel arch B131 and a portal steel frame 132; the inner side of the reinforcing ring structure is provided with a steel arch B131 with 4I 22B in double splicing, the outer side of the reinforcing ring structure is provided with a door-shaped steel frame 132 with 2I 22B in double splicing, and a door-shaped steel frame beam 1321 is welded with the steel arch B131 in sections; the steel arch and the portal steel frame 13 and the steel arch A11 are adopted 25 Longitudinal steel bars are connected, and the circumferential spacing of the connecting steel bars is 1m;
The door-shaped steel frame 132 consists of a beam 1321 and a column 1322, wherein a gap between the beam 1321 and the steel arch B131 is connected by adopting a vertical support 1323, and sprayed concrete at the gap is backfilled tightly;
Preferably, the vertical support 1323 may be a vertical support made of section steel 22 b;
Preferably, the door-shaped steel frame beam 1321 is welded with the steel arch B131 in a segmented manner, and the specific steps include:
The vertical supports 1323 are fixedly connected with the arc-shaped steel arch B131, the distance between every two adjacent vertical supports 1323 is 0.5m, the beam 1321 is considered to be difficult to construct once, the beam 1321 is fixedly connected with the vertical supports 1323 by adopting a multiple lengthening method, and two ends of the vertical supports 1323 are welded and fixed; the sectional lengthening installation of the beam 1321 and the longitudinal up-step excavation of the support hole 22 are synchronously carried out;
For example, the mounting sequence is: firstly, mounting a beam 1321, a vertical support 1323 and a stand column 1322 with the length of 4.7m, gradually lengthening the beam 1321 and increasing the vertical support 1323 along with the longitudinal step excavation construction of the support hole 22, and performing welding connection of the vertical support 1323; the screen hanging and slurry spraying are timely carried out every time the door-shaped steel frame 132 completes the sectional installation; the beam 1321 is lengthened by adopting a connecting plate, and two ends of the vertical support 1323 are welded and fixed;
the beam 1321 is used as a supporting point of the supporting arch, 8 system anchor rods and 4 anchor rods are additionally arranged on each side of the door-shaped steel frame 132 42 Locking the foot anchor tube 23;
3. Top-picking construction for branch hole 12 entering branch hole 22
And backfilling core soil at the intersection of the construction fork hole 12 and the support hole 22, then entering the support hole 22 in a small pilot hole mode, supporting by adopting a small pilot hole steel frame 25 (a work 20a portal steel frame) in the support hole 22, gradually lifting the top elevation of the small pilot hole steel frame 25 of the support hole 22 along with deep excavation, reaching the top elevation of the support hole 22 at the center line of the support hole 22, and excavating an excavation height which is larger than the excavation contour line of the support hole 22, wherein the reserved deformation amount and temporary support thickness are considered in construction, the overstretching amount at the position is 0.6m, and the reserved deformation amount is 0.3m. The temporary support of the steel frame is followed in time in the construction process, and after the pilot tunnel is excavated and supported to the other end of the support tunnel 22, the support tunnel primary support steel frame 24 at the top of the support tunnel 22 is erected in time.
The small pilot tunnel steel frame 25 adopts I20a section steel, the distance is 80cm, and 2 steel frame feet are arranged at each position42 Locking the foot anchor pipe 23, and timely performing net hanging and slurry spraying in the construction process; the vertical support hole 22 is used for tunnel excavation, the tunnel excavation width is 4.9m, the excavation height is 0.6m above the tunnel positive hole excavation contour line, and the tunnel upper step is excavated in a mode of reserving core soil; the early excavation of the roadway adopts a fold line to be picked up so as to be connected with the arch part of the fork hole section in sequence, and the arch part of the inclined roadway adopts a rectangle after a certain distance is excavated, so that primary compaction with the branch hole 22 is facilitated.
In construction, a top steel frame beam (a section steel beam of a work 20 a) in the temporary support system of the small pilot tunnel is positioned outside a primary support steel frame 24 of a support tunnel 22, and is not taken out when a support tunnel arch is applied in the next step, so that the arch crown of the small pilot tunnel is high Cheng Chaochu, and an excavation line is designed for the positive tunnel so as to meet the requirements of temporary support thickness and reserved deformation (in the span range of the transverse tunnel, the reserved deformation of the positive tunnel is set according to 30 cm).
4. Initial support of support hole 22
After the roof construction of the support hole 22 is finished, the support hole primary support construction is carried out on the inner side of the excavated section according to the primary support parameters of the support hole 22, one end of a support hole primary support steel frame 24 (14) is erected on the upper portion of the beam 1321 within the range of an intersection, the other end of the support hole primary support steel frame 24 is supported on a steel plate, the row spacing between the adjacent support hole primary support steel frames 24 is 0.5m, the joint position and the arch foot position of the support hole primary support steel frame 24 are additionally provided with a foot locking anchor pipe, the length of the anchor pipe is 3.5m, cement paste is injected, and the foot locking anchor pipe is firmly welded with the support hole primary support steel frame 24 to prevent the arch frame of the support hole primary support steel frame 24 from sinking. Measuring pay-off marks on the side wall of the pilot tunnel after the primary support of the step on the pilot tunnel in the pilot tunnel is completed, removing temporary supports on one side of a small pilot tunnel steel frame 25, performing primary support in the direction of the pilot tunnel, excavating an upper arc pilot pit, excavating for 10m forwards, spraying concrete to seal the tunnel face 21, and suspending excavation in the direction; and turning around and removing temporary support on the other side of the small pilot tunnel steel frame 25, performing primary support in the direction of the pilot tunnel, excavating an upper arc pilot tunnel, excavating for 10m forwards, spraying concrete to seal the tunnel face 21, and suspending excavation in the direction. When the arc pilot tunnel of the upper step expands and digs, the reserved deformation of the arch crown of the supporting hole is gradually reduced, and meanwhile, lengthening and mounting of the cross beam above the reinforcing ring are carried out. After the construction space is satisfied, the working surfaces on the two sides can be constructed simultaneously, and the inverted arch is ensured to be closed as soon as possible within the width range of the fork hole. The inverted arch steel frame (namely the bottom steel frame of the primary support steel frame of the support hole) within the width range of the fork hole is connected with the bottom transverse strut steel frame of the final reinforcing ring (namely the steel frame at the bottom of the reinforcing ring) of the fork hole, so that the primary support and the inverted arch form a ring, and the construction safety is ensured. In the top-picking construction process, advanced support is timely implemented, and in addition, the secondary lining structure in the crossing range should be timely implemented in a closed loop construction after the primary support steel frame is looped.
Preferably, the tunnel face 21 is sprayed with C25 concrete to a thickness of 20 cm;
Preferably, the reinforcement ring is provided with out-of-plane anti-overturning stability assurance measures: before the primary support steel frame 24 of the support hole is erected, a large horizontal force is generated on the top end of the reinforcing ring structure after primary support stress in the range in the later period is considered, and in order to ensure the stability of the reinforcing ring structure, the inclined supports are required to be arranged on two sides of the fork hole 12 to offset the horizontal force which causes instability of the ring beam, meanwhile, the horizontal displacement of the top end of the limiting ring beam of the spray mixing thickness is increased at the rear part of the top of the reinforcing ring structure, and in addition, the horizontal displacement of the bottom end of the supporting limiting ring beam vertical to the ring beam is arranged on one side of the support hole in front of the bottom part of the reinforcing ring structure, so that the stability of the reinforcing ring structure after primary support stress of the support hole is ensured.
Design checking calculation of reinforcing ring structure
A. calculation idea
According to the structural stress analysis, according to the plane strain assumption, a structure-load model is adopted, and according to the burial depth of an underground structure and the geological characteristics of a penetrating soil layer, the structural earthing is converted into the upper earthing load and the lateral earthing pressure, and the upper earthing load and the lateral earthing pressure are applied to the structure to calculate the structural internal force.
Firstly, calculating the concentrated load of the primary support structure acting on the reinforcing ring steel frame in the range of the fork and branch hole interface under the condition of deep burying of V-level surrounding rock, and then checking the reinforcing ring steel frame according to the concentrated load. The primary support structures of the support holes and the fork holes are constructed according to the design drawing, checking calculation is not carried out at the primary support structures, and the safety of the interface position reinforcing ring steel frame is checked only.
B. Calculating the concentrated load of the primary support steel frame 24 on the reinforcing ring
According to the hydraulic tunnel design Specification (SL 279-2016), the surrounding rock of the broken dispersion structure, the surrounding rock pressure acting on the lining can be calculated as follows:
Vertical direction: q v=（0.2~0.3）γR b, horizontal: q h=（0.05~0.10）γR h
Wherein gamma R is the volume weight of the rock mass, b is the tunnel excavation width, and h is the tunnel excavation height;
The underground water activities are generally in a dripping-linear flowing state during tunnel construction, only primary support stress is calculated at the position, and the action of external water pressure is not considered; the action of the earth reaction force acted by the bottom plate is simulated by the earth spring; the calculated width is taken as unit length.
C. checking calculation reinforced ring steel frame
The concentrated load is obtained according to the calculation result of the previous stage; calculating the lateral soil pressure according to Q h=（0.05~0.10）γR h, and considering the calculated width of the lateral load; the vertical earth pressure does not act directly above it and is therefore not considered; the action of the earth reaction force on the bottom plate is simulated by the earth spring.
The traditional scheme considers the limitation of structural stress, only considers that 12 primary support steel frames of the support holes in the range of the reinforcing ring act on the reinforcing ring, and the rest 2 primary support steel frames are independently closed to form a ring, so that the load does not act on the reinforcing ring. According to the steel frame beam unit stress diagram, the beam unit stress at the intersection point is the largest (the setting of the pull rod is considered here), and the steel frame beam unit stress is 186633.2kN/m 2, and the steel frame does not exceed the design value 215000kN/m 2 of tensile strength and compressive strength due to the fact that Q235 steel is adopted by the steel frame. If no tie rods are provided, the steel frame beam unit stresses will become greater.
The optimization scheme considers that 14 primary support steel frames 24 of the support holes in the range of the reinforcing ring all act above the reinforcing ring. According to the steel frame beam unit stress diagram, the beam unit stress at the intersection point is the largest (the setting of the pull rod is considered here), and the steel frame beam unit stress is 156532.7kN/m 2, and the steel frame does not exceed the design value 215000kN/m 2 of tensile strength and compressive strength due to the fact that Q235 steel is adopted by the steel frame. It can be seen that the optimized solution is more focused than the original solution, whereas the stresses of the steel frame girder elements are smaller.
1. Aiming at the characteristic of poor stability of surrounding rock under V-level surrounding rock, the invention provides a top-picking construction scheme of a hydraulic tunnel fork turning support hole, which can greatly improve construction efficiency, ensure construction safety and provide reference for similar engineering.
2. The method simplifies and analyzes the stress conversion of the main beam and the secondary beam of the cross section supporting structure, combines the standard and adopts a two-dimensional calculation model to analyze the stress condition of the supporting structure, and uses the stress condition as the design basis of the reinforcing ring steel frame at the intersection position, thereby ensuring the stress stability of the reinforcing ring steel frame.
3. The invention provides a novel reinforcing ring structure form (an inner double-spliced 4-truss steel arch frame and an outer double-spliced 2-truss portal steel frame) in the top-picking range, meanwhile, pull rods are additionally arranged on two sides of the top of the arch frame (the outermost vertical supports 1323 on the left side and the right side are pull rods), and the structural form can be found to be more reasonable in stress by combining calculation and analysis, so that the excessive concentration of stress on the arch frame foot is avoided, and the stress stability of the reinforcing ring steel frame is improved.
4. The invention combines the difficulty of site construction, and provides a method for installing the portal steel frame beam in a segmented way, which is convenient for site installation and construction.
5. Aiming at the stress characteristics of the reinforcing ring steel frame, the invention provides corresponding construction measures for ensuring the overall anti-overturning stability of the reinforcing ring steel frame outside the plane, and improves the overall stability of the support system.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. The hydraulic tunnel fork-hole-to-branch-hole roof-picking construction method is characterized by comprising the following steps of:
1. construction of transition section between fork hole (12) and branch hole (22)
The junction transition section of the fork hole (12) and the branch hole (22) is excavated by adopting a step method, the primary support steel frame adopts a special-shaped steel frame, the special-shaped steel frame is erected away from the normal, the direction and the arch height of the special-shaped steel frame are gradually adjusted, and the steel arch A (11) is gradually lengthened;
2. construction of reinforcing ring of fork hole (12) at intersection section of fork hole (12) and branch hole (22)
After the profile line is excavated from the construction fork hole (12) to the branch hole (22), an advanced support and reinforcing ring structure is applied at the intersection; the reinforcing ring structure is a steel arch frame and a portal steel frame (13); the steel arch and the portal steel frame (13) comprise a steel arch B (131) and a portal steel frame (132); the inner side of the reinforcing ring structure is provided with a double-spliced steel arch B (131) with 4 steel frames, the outer side of the reinforcing ring structure is provided with a double-spliced door-shaped steel frame (132) with 2 steel frames, and the door-shaped steel frame cross beam (1321) is welded with the steel arch B (131) in a segmented manner;
the door-shaped steel frame (132) consists of a beam (1321) and an upright post (1322), a gap between the beam (1321) and the steel arch B (131) is connected by adopting a vertical support (1323), and the gap is filled with sprayed concrete in a backfilling manner;
The door-shaped steel frame (132) is welded with the steel arch B (131) in a segmented mode, and the concrete steps include: the vertical supports (1323) are fixedly connected with the arc-shaped steel arch B (131), the distance between every two adjacent vertical supports (1323) is 0.5m, the cross beam (1321) is fixedly connected with the vertical supports (1323) by adopting a multiple lengthening method, and the vertical supports (1323) are fixedly connected with the steel arch B (131) by welding; the sectional lengthening installation of the beam (1321) and the longitudinal step excavation of the support hole (22) are synchronously carried out;
3. top-picking construction for entering branch hole (22) from branch hole (12)
Backfilling core soil at the intersection of a construction fork hole (12) and a support hole (22), then entering the support hole (22) in a small pilot hole mode, supporting by adopting a small pilot hole steel frame (25) in the support hole (22), gradually lifting the top elevation of the small pilot hole steel frame (25) of the support hole (22) along with deep excavation, reaching the top elevation of the support hole (22) at the central line of the support hole (22), enabling the excavation height to be larger than the excavation contour line of the support hole (22), temporarily supporting the steel frame in time, and immediately following the excavation of the pilot hole to the other end of the support hole (22), and then immediately erecting a support hole primary support steel frame (24) at the top of the support hole (22);
The vertical support hole (22) is used for excavating a roadway, and a step on the roadway is excavated by adopting a reserved core soil mode; the early excavation of the roadway adopts a fold line to be picked up so as to be connected with the arch part of the fork hole section in sequence, and the arch part of the inclined roadway adopts a rectangle after a certain distance is excavated;
4. Initial support of support hole (22)
After the roof construction of the support hole (22) is finished, carrying out support hole primary support construction on the inner side of an excavated section according to primary support parameters of the support hole (22), wherein one end of a support hole primary support steel frame (24) is erected on the upper part of a beam (1321) within the range of an intersection, the other end of the support hole primary support steel frame (24) is supported and cushioned on a steel plate, foot locking anchor pipes are additionally arranged at the sections and arch feet of the support hole primary support steel frame (24), cement paste is injected, and the foot locking anchor pipes are firmly welded with the support hole primary support steel frame (24); measuring pay-off marks on the side wall of the pilot tunnel to mark a pilot tunnel digging contour line after the primary support of the step on the pilot tunnel in the pilot tunnel is completed, removing the temporary support on one side of the small pilot tunnel steel frame, performing primary support in the pilot tunnel direction, digging an upper arc pilot pit, digging forward, spraying concrete to seal a tunnel face (21), and suspending the digging in the direction; turning around and removing temporary support on the other side of the small pilot tunnel steel frame, performing primary support in the direction of the pilot tunnel, excavating an upper arc pilot tunnel, excavating forwards, spraying concrete to seal the tunnel face (21), and suspending excavation in the direction; when the arc pilot pit of the upper step is dug, the reserved deformation of the arch crown of the branch hole is gradually reduced; the branch hole inverted arch steel frame within the width range of the branch hole is connected with the bottom transverse strut steel frame of the last reinforcing ring of the branch hole, so that the branch hole primary support steel frame within the range of the intersection is looped as soon as possible.
2. The hydraulic tunnel fork-turning support-roof construction method according to claim 1, wherein 8 steel frames are arranged for each steel frame of the fork42 Pin locking anchor pipes and steel arches A (11) are adopted/>25 Longitudinal steel bars are connected, and the circumferential spacing of the connecting steel bars is 1m.
3. The hydraulic tunnel fork-turning support-roof construction method according to claim 2, characterized in that the arch part of the fork (12) is installed within 120 DEG range42 Leading small catheter, arch part adopting/>25 Explosive roll anchor rod, side wall adopts/>25 Mortar anchor rods; the arch wall and the inverted arch are protected by C25 concrete.
4. The hydraulic tunnel fork-turning support roof-picking construction method according to claim 3, wherein the fork transition steel arch A (11) adopts an I18 steel arch, and the steel arches are arranged in a fan shape.
5. The hydraulic tunnel fork-turning support roof-picking construction method according to claim 4, wherein the steel arch and the portal steel frame (13) and the steel arch A (11) are adopted25 Longitudinal steel bars are connected, and the circumferential spacing of the connecting steel bars is 1m.
6. The hydraulic tunnel fork-turning support roof-picking construction method according to claim 5, characterized in that 8 system anchors and 4 anchor rods are added on each side of the portal steel frame (132)42 Locking the foot anchor tube.
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