CN114370288A - A kind of strengthening device and construction method for initial support collapse treatment of highway tunnel - Google Patents

Abstract

The invention discloses a reinforcing device for treating collapse of primary support of a highway tunnel and a construction method thereof, wherein the reinforcing device comprises a tunnel body, the tunnel body comprises a collapse cavity and parts which are not collapsed and are arranged at two ends of the collapse cavity, a hole slag counter-pressure pile is arranged on the collapsed hole slag which is collapsed in the tunnel body, a concrete layer is arranged on the collapsed hole surface of the collapse cavity in the tunnel body, a supporting device is also arranged in the tunnel body, and concrete is filled between the supporting device and the collapsed hole surface; the reinforcing device for the collapse treatment of the primary support of the highway tunnel and the construction method thereof can effectively guarantee the construction quality and construction safety of engineering, accelerate the construction progress, create higher economic benefit, greatly improve the collapse treatment level of the primary support of the highway tunnel, and further meet the construction requirements.

Description

A kind of strengthening device and construction method of initial support collapse treatment of highway tunnel

technical field

The invention relates to the technical field of treatment of tunnel collapse, in particular to a strengthening device for treatment of initial support collapse of a highway tunnel and a construction method thereof.

Background technique

The initial support collapse of highway tunnels caused by various geological disasters has been studied by scholars at home and abroad. One of the common risks. At present, the traditional construction measures for the treatment of tunnel collapse are reverse backfilling of the tunnel face, advance grouting reinforcement of small pipes, reinforcement of double-layer steel arches, etc. support. The conventional methods of treating the collapse of tunnel primary support are mainly to deal with measures such as adding advanced bolt reinforcement, increasing the type of support steel frame, and increasing the thickness of lining support. Because the original surrounding rock is exposed after the collapse of the initial support of the tunnel, the stability of the collapsed area is poor, the traditional construction measures cannot guarantee the safe construction of the treatment personnel, and the treatment effect is not very satisfactory, and the traditional technology often has a long construction period and a high cost. , can not meet the needs of use.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above problems and provide a kind of effective guarantee of engineering construction quality and construction safety, speed up the construction progress, not only create higher economic benefits, but also greatly improve the treatment level of initial support collapse of highway tunnels, and then The invention relates to a strengthening device and a construction method for the treatment of initial support collapse of a highway tunnel that meet construction requirements.

In order to achieve the above purpose, the technical scheme of the present invention is as follows: an initial support collapse treatment strengthening device for a highway tunnel, comprising a tunnel body, the tunnel body includes a collapsed cavity and an uncollapsed portion at both ends of the collapsed cavity, and the tunnel body A cavern slag back pressure stack is arranged on the collapsed cave slag, a concrete layer is provided on the collapsed cavity surface of the tunnel body, and a support device is also provided in the tunnel body, and the support device is connected with the collapsed cavity. Fill the cavity with concrete.

Preferably, the supporting device includes an arched structure, a steel frame structure and a steel pipe support structure, the arched structure is a concrete construction foundation and is installed at one of the uncollapsed parts, and the steel frame structure is evenly erected in an arc shape In the tunnel, one end of the steel pipe support structure is inserted into the sleeve arch structure, and the other end extends into the other uncollapsed part, wherein the steel pipe support structure is fixed on the steel frame structure, and the steel frame structure and the collapsed cavity surface are between Fill with concrete.

Preferably, the surface of the steel pipe support structure is provided with a plurality of through holes.

Preferably, the steel pipe support structures are evenly distributed on the steel frame structure in a fan shape.

Preferably, every two adjacent steel tube support structures are set up in a dislocation up and down.

The invention also discloses a construction method of a strengthening device for treating the collapse of initial support of a highway tunnel, comprising the following steps:

S1: For the slightly deformed section of the initial support, chisel off the shotcrete that falls off the initial support, re-install the rock bolt and hang the net to replenish the shotcrete;

S2: For the cracked section of the initial support, the compound arch steel frame is used for rigid support to prevent further traction damage in the collapsed section of the initial support, and a small grouting pipe is used simultaneously to consolidate the grouting in the radial direction to maintain the stability of the surrounding rock;

S3: The distortion failure section of the initial support steel frame, for the position closest to the collapsed section, after the initial support is stabilized by grouting, the arches are replaced one by one.

S4: For the treatment of the collapsed section of the initial support, first carry out the back pressure stacking of the cave slag to prevent further traction damage to the collapsed part, and spray concrete to seal the cave slag surface, then pre-buy the pumping pipe and use C20 concrete to backfill the collapse cavity, and then apply Long-distance follow-up large tube shed advanced support;

S5: After the advance support is completed, the core soil is excavated and supported by the circumferential cutting cycle by cycle. Small grouting pipes are used to consolidate the loose and collapsed slag while the support is being excavated. soil excavation support;

S6: Use high-grade secondary lining concrete and reinforcing steel bars for lining construction to form a stable and reliable permanent lining structure.

Preferably, in the step S1, an excavation trolley is used as a treatment platform, and an air pick is used to chisel the initial cracked shotcrete. The φ22 coiled anchor rod with a length of 3.5m, the spacing between the anchor rods is 1.2m×1.2m, and the φ8 reinforced mesh is hung close to the shotcrete surface, and the mesh spacing is 20cm×20cm. concrete.

Preferably, in the step S2, the following steps are included:

S201: Rigid support of compound arch steel frame;

S202: grouting of surrounding rock with radial consolidation of conduit;

The step S201 includes:

① First, I20b steel support is used, with a distance of 60cm, and rigid support is carried out to prevent the collapse and instability of the primary support;

②The gap between the compound arch steel frame and the initial support is closed with C25 shotcrete;

③ After the complex arch is installed, use Φ22 steel bar as the longitudinal connecting bar to connect the adjacent arches together, so that the arches form a whole;

④ Add φ42 small conduits with a length of 4.5m as the steel frame locking feet. The locking feet are located on both sides of the steel frame at the arch waist and arch foot, 2 pieces are arranged in each place, and the welding between the small conduits and the steel frame is strengthened.

Preferably, in the step S3, the following steps are included:

S301: After the initial support twist failure section is treated and stabilized, backfill the hole slag to provide an operating platform for the later construction, and use this to back pressure the initial support on both sides to prevent the initial support from collapse and collapse, and keep turning forward with the advancement of the arch change. The slag body below circulates back and forth;

S302: The arch change is carried out in sequence from the upper and lower steps. Hydraulic breakers are used to chisel the sprayed concrete on both sides of the steel frame. The width of the first chisel is slightly wider than that of the steel support. One section is removed and a section of steel support is installed. ; When changing the second one, the cutting width is the design width between the first one and the second one, and the subsequent arch-changing methods such as the third one and the fourth one are the same as the second one.

Preferably, in the step S4, the following steps are included:

S401: After the surrounding rock of the collapsed cavity is stabilized, the slag backpressure is first carried out to prevent further traction damage to the collapsed part, and C25 shotcrete is used to seal the slag surface of the cavity;

S402: Pre-embed the pumping pipe and use C20 concrete to backfill the collapsed cavity, and the total backfill height should be no less than 5m above the vault to ensure the safety of the later excavation and the structure of the cave;

S403: Long-distance advance follow-up pipe shed support;

S404: After the advanced support consolidation is completed, the collapsed section of the initial support is re-excavated and supported. The face of the loose slag body in each cycle is sealed with C25 shotcrete, and the loose slag body is grouted with φ42 small radial pipes to consolidate the loose slag body. The core soil is reserved by circular cutting.

The invention discloses an initial support collapse treatment strengthening device for a highway tunnel and a construction method thereof, comprising a tunnel body, the tunnel body comprising a collapsed cavity and uncollapsed parts at both ends of the collapsed cavity, and the collapsed slag in the tunnel body There is a slag back pressure pile on the tunnel body, a concrete layer is arranged on the collapsed cavity surface of the tunnel body, and a support device is also arranged in the tunnel body, between the support device and the collapsed cavity surface Filled with concrete; the strengthening device and its construction method for the treatment of the initial support collapse of the highway tunnel can effectively ensure the construction quality and construction safety of the project, and speed up the construction progress, which not only creates higher economic benefits, but also greatly improves the initial support of the highway tunnel. Collapse treatment level, and then meet the construction needs.

Description of drawings

FIG. 1 is a schematic structural diagram 1 of a first stage support collapse treatment strengthening device of a highway tunnel according to the present invention.

FIG. 2 is a second structural schematic diagram of a strengthening device for treating collapse of initial support of a highway tunnel according to the present invention.

FIG. 3 is a top view of a strengthening device for treating collapse of initial support of a highway tunnel according to the present invention.

FIG. 4 is a left side view of a strengthening device for treating collapse of initial support of a highway tunnel according to the present invention.

FIG. 5 is an enlarged schematic view of the structure at A in FIG. 2 of the present invention.

FIG. 6 is a schematic flow chart of a construction method of a road tunnel initial support collapse treatment strengthening device according to the present invention.

In the figure: 1. Tunnel body; 11. Collapse cavity; 12. Slag backpressure reactor; 13. Uncollapsed part; 2. Concrete layer; 3. Supporting device; 31. Set arch structure; 32. Steel frame structure 33. Steel pipe support structure.

Detailed ways

The present invention will now be described in further detail with reference to the accompanying drawings. The accompanying drawings are simplified schematic diagrams, and only illustrate the basic structure of the present invention in a schematic manner, and thus only show the structures related to the present invention.

Please refer to FIGS. 1-6 , a strengthening device for treating collapse of initial support of a highway tunnel, including a tunnel body 1 , and the tunnel body 1 includes a collapsed cavity 11 and uncollapsed portions 13 at both ends of the collapsed cavity 11 . Since the tunnel body 1 In case of internal collapse, non-collapsed parts 13 will inevitably be formed on both sides of the cavern 11. The collapsed cavern in the tunnel body 1 is provided with a cavern slag back pressure pile 12. When the tunnel collapses, the top gravel, concrete Blocks and the like will fall to the surface of the tunnel. At this time, a slag back pressure stack 12 is set on these gravels. The slag back pressure stack 12 is C25 shotcrete, which can effectively prevent the collapsed part from being further damaged by traction; A concrete layer 2 is provided on the collapsed cavity surface of the collapsed cavity 11. The concrete layer 2 can improve the stability, prevent the top gravel from falling further, and can also facilitate the connection of the concrete filled below. The tunnel body 1 is also provided with a support. The support device 3 is filled with concrete between the support device 3 and the surface of the collapsed cavity.

In the solution of the present invention, the support device 3 includes an arched structure 31, a steel frame structure 32 and a steel pipe support structure 33. The arched structure 31 is a concrete construction foundation and is located at one of the non-collapsed parts 13. That is to say, the sleeve arch structure 31 is the foundation built before the collapse is repaired, which is convenient for subsequent construction. The steel frame structure 32 is evenly erected in the tunnel in an arc shape, and one end of the steel pipe support structure 33 is inserted into the sleeve arch structure 31. The other end extends into the other non-collapsed portion 13, wherein the steel pipe support structure 33 is fixed on the steel frame structure 32, and concrete is filled between the steel frame structure 32 and the surface of the collapsed cavity, wherein the surface of the steel pipe support structure 33 is provided with concrete. There are multiple through holes.

During the specific construction, since the surface of the steel pipe support structure 33 is provided with a plurality of through holes, and one end of the steel pipe support structure 33 is inserted into the collapsed part 13, the other end of the steel pipe support structure 33 is connected with a grouting joint, and the Two-liquid slurry is injected into the steel pipe support structure 33, the initial pressure of grouting is 0.5-1MPa, and the final pressure is 2.0MPa, and the two-liquid slurry will overflow from the through holes provided on the surface of the steel pipe support structure 33, and will loosen the slump. The rock is knocked down to mix the rock with the slurry, thereby improving the stability of the overall slurry, and also improving the rigidity and strength of the steel pipe support structure 33; further, C20 concrete is cast around the steel pipe support structure 33, and the total backfill height reaches the vault. The above shall not be less than 5m.

As a preferred solution, the steel pipe support structures 33 are evenly distributed on the steel frame structure 32 in a fan shape (as shown in FIG. 3 ). The fan shape arrangement can increase the support area and further improve the stability.

Based on the above embodiment, every two adjacent steel tube support structures 33 are set up and down in a dislocation (as shown in FIG. 4 ), and are also fixed on the steel frame structure 32 , which can increase the depth and length and improve the overall strength.

The invention also discloses a construction method of a strengthening device for treating the collapse of initial support of a highway tunnel, comprising the following steps:

S1: For the slightly deformed section of the initial support, chisel off the shotcrete that falls off the initial support, re-install the rock bolt and hang the net to replenish the shotcrete;

S2: For the cracked section of the initial support, the compound arch steel frame is used for rigid support to prevent further traction damage in the collapsed section of the initial support, and a small grouting pipe is used simultaneously to consolidate the grouting in the radial direction to maintain the stability of the surrounding rock;

S3: The twisted failure section of the initial support steel frame, for the position closest to the collapsed section, after the initial support is stabilized by grouting, the arches are replaced one by one. , strictly prohibit shooting" reinforcement policy to carry out construction;

S4: For the treatment of the collapsed section of the initial support, first carry out the back pressure stacking of the cave slag to prevent further traction damage to the collapsed part, and spray concrete to seal the cave slag surface, then pre-buy the pumping pipe and use C20 concrete to backfill the collapse cavity, and then apply Long-distance follow-up large tube shed advanced support;

S5: After the advance support is completed, the core soil is excavated and supported by the circumferential cutting cycle by cycle. Small grouting pipes are used to consolidate the loose and collapsed slag while the support is being excavated. soil excavation support;

S6: Use high-grade secondary lining concrete and reinforcing steel bars for lining construction to form a stable and reliable permanent lining structure.

Because the initial support structure of highway tunnels generally causes different degrees of cracking and deformation after the initial support of the road tunnel collapses. : Slightly deformed segment, cracked segment, twisted failure segment and collapsed segment.

In the solution of the present invention, in the step S1, an excavation trolley is used as a treatment platform, and an air pick is used to chisel the initial support cracked shotcrete. Re-install φ22 coiled anchor rods with a length of 3.5m, the spacing between anchor rods is 1.2m×1.2m, hang φ8 steel mesh sheets close to the shotcrete surface, and the mesh spacing is 20cm×20cm. Spray C25 shotcrete.

In the step S2, the following steps are included:

S201: Rigid support of compound arch steel frame;

S202: grouting of surrounding rock with radial consolidation of conduit;

The step S201 includes:

① First, I20b steel support is used, with a distance of 60cm, and rigid support is carried out to prevent the collapse and instability of the primary support;

②The gap between the compound arch steel frame and the initial support is closed with C25 shotcrete;

③ After the complex arch is installed, use Φ22 steel bar as the longitudinal connecting bar to connect the adjacent arches together, so that the arches form a whole;

④ Add φ42 small conduits with a length of 4.5m as the steel frame locking feet. The locking feet are located on both sides of the steel frame at the arch waist and arch foot, 2 pieces are arranged in each place, and the welding between the small conduits and the steel frame is strengthened.

The step S202 includes:

① The effective reinforcement range of the surrounding rock radial grouting is 3.5m outside the tunnel excavation outline. The circumferential spacing of the grouting holes is 150cm and the longitudinal spacing is 150cm. The ×5mm hot-rolled seamless steel pipe is used as the orifice pipe. The grouting hole is at 90° to the tunnel circumferential contour. The difficult part of the vault is drilled, the angle is adjusted to 60°, and the hole depth is 350cm.

② When the surrounding rock fissure water is not developed, pure cement slurry is used; when the fissure water is developed, the grouting material adopts cement-water glass double slurry, C:S=1:0.5, and the water-cement ratio of cement slurry is 0.8:1. For a grouting section, from both sides to the middle, it is applied in two sequences, and for the same row of holes, the sequence is from top to bottom. In general, one-shot grouting is used for the whole hole. When the porosity is poor, forward grouting should be used in two stages.

The step S3 includes the following steps: S301: After the initial support distortion failure section is treated and stabilized, backfill the hole slag to provide an operating platform for the later construction, and use this to back pressure the initial support on both sides to prevent the initial support from collapsing. With the advancement of the arch changing, the lower slag body is continuously turned forward, and the cycle goes back and forth; S302: The arch changing is performed from the upper and lower steps in sequence, and the hydraulic breaker is used to chisel the sprayed concrete on both sides of the steel frame, and the width of the first chisel is In order to be slightly wider than the steel support, remove one section and install a steel support; when replacing the second one, the cutting width is the design width between the first one and the second one; after the twisted steel frame is removed, re-support The protective steel frame is made of I20b I-beam, and the locking feet are made of 4.5m long φ42 small conduits; φ8 steel mesh sheets are hung on the back of the steel frame, and the mesh spacing is 20cm×20cm; and C25 shotcrete is used to seal, and the third and third The way of changing the arch of the fourth yam is the same as that of the second yam.

In the step S4, the following steps are included:

S401: After the surrounding rock of the collapsed cavity is stabilized, first carry out the back pressure stacking of the cave slag to prevent further traction damage to the collapsed part, and use C25 shotcrete to close the cave slag surface. The back pressure cave slag must be stacked densely, which can effectively block the collapse surface. Continue to expand and provide an operating platform for later construction;

S402: Pre-embed the pumping pipe and use C20 concrete to backfill the collapsed cavity. The total backfill height is not less than 5m above the vault to ensure the safety of the later excavation and the structure of the cave. The pumping backfill is implemented in two stages: the first stage Pumping after the completion of the tunnel slag sealing, pumping before the secondary lining pouring in the second stage; S403: Long-distance advanced follow-up pipe shed support, after the collapse of the highway tunnel, the collapsed body and the backfilling slag body form a new face The rock mass and surrounding rock gaps are loose and broken, the common pipe shed is easy to collapse after drilling, and the pipe shed cannot be sent in later, and the supporting length of the common pipe shed obviously does not meet the longitudinal length of the collapsed section. In order to solve the above problems, this patent proposes to adopt the long-distance advanced follow-up pipe shed support technology, which can not only solve the problem of hole formation, but also meet the requirements of long-distance support;

① First, construct the arch structure with the tube shed, reserve a guide bracket studio at the collapsed end of the initial support, erect 4 I18 steel frames on the arch foot platforms on both sides of the initial support, and weld and fix the guide tubes on the steel frame. , The guide pipe is made of φ127 hot-rolled steel pipe, with a wall thickness of 6mm and a spacing of 40cm. The sleeve arch is poured with C30 concrete, and the steel frame and guide pipe are poured into the sleeve arch concrete. The sleeve arch is 2m in length and 50cm in thickness, and the end of the sleeve arch is close to the slag backfill surface of the collapsed cave;

② The total length of the pipe shed is designed to be 40m, and the length of each section is 2m, which is connected by a sleeve thread. The drilling equipment adopts rotary and impact drilling. In order to speed up the construction speed, an eccentric bit is used and the casing pipe can be automatically followed. The pipe shed should be constructed according to the designed position, and the vertical axis direction of the drilling rig must be accurately controlled to ensure the correct orientation of the orifice. During drilling, the inclinometer should be used to measure the deflection of the pipe shed and correct it in time;

③ After the drilling is completed, withdraw the drill pipe, leave the guide pipe, and connect the grouting joint to carry out the grouting of the advanced supporting surrounding rock. The grouting material adopts double-liquid slurry, and its initial parameters are: water-cement ratio w/c=0.6～0.8, cement slurry/water glass=1:0.05 (volume ratio), water glass concentration=35～40°Be′, The modulus of water glass is m=2.6, and the strength grade of grouting cement is 42.5;

④ When grouting, the grouting should be carried out according to the principle of first up and then down, first thin and then thick. The amount of grouting is mainly controlled by pressure, and the amount of grouting is checked. The initial pressure of grouting is 0.5-1MPa, and the final pressure is 2.0MPa. The grouting pressure of each hole reaches 2.0MPa, and the grouting can be stopped after maintaining for more than 10min. After grouting, remove the grout in the pipe in time, and fill it with M30 cement mortar to enhance the rigidity and strength of the pipe shed; S404: After the advanced support consolidation is completed, the initial support collapsed section is re-excavated for support, and the excavation of the collapse section is mainly The mechanical excavation is carried out with a breaker, and blasting and other operations that strongly disturb the surrounding rock are strictly prohibited; the face of the loose slag body in each cycle is sealed with C25 shotcrete, and the loose slag body is consolidated by grouting with a φ42 radial small pipe. The reserved deformation of the excavation is 30cm, and the core soil is reserved by circular cutting.

① The initial support parameters of the collapsed section are as follows: C25 shotcrete is used, I20b I-beam is used for the steel frame support, the spacing is 60cm/square, and the φ22 radial coil anchors with a length of 3.5m are re-installed, and the spacing between the anchors is 1.2m× 1.2m; φ8 reinforced mesh is hung close to the surrounding rock surface, the mesh spacing is 20cm×20cm, and the end of the anchor rod is used to fix it; the bottom of the steel frame and the arch waist are set with a 4.5m-long lock foot grouting small pipe;

② The secondary lining parameters of the collapsed section are as follows: C40 impermeable concrete is used, the thickness of the reinforced concrete secondary lining is 60cm, the main lining bars are φ22, the spacing is 20cm, and the distribution bars are φ16, and the spacing is 20cm;

③ Before the construction of the secondary lining, waterproof and drainage should be applied first. The tunnel lining adopts the composite waterproof layer of geotextile + EVA waterproof board, the circumferential direction adopts FH50 soft permeable pipe, and the longitudinal direction adopts HDPE DN/ID100 perforated double-wall corrugated pipe.

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (10)

1. The utility model provides a highway tunnel preliminary bracing collapse punishment reinforcing means, includes the tunnel body, the tunnel body is including the cavity of collapsing and the portion that does not collapse at cavity both ends that collapses, its characterized in that, be equipped with hole sediment back pressure heap on the hole sediment that collapses in the tunnel body, be equipped with concrete layer on the cavity face of collapsing of the cavity of collapsing in the tunnel body, still be equipped with supporting device in the tunnel body, concrete is filled between supporting device and the cavity face of collapsing.

2. The device as claimed in claim 1, wherein the supporting device comprises an arch-covered structure, a steel frame structure and a steel pipe supporting structure, the arch-covered structure is a concrete construction foundation and is arranged at one part which is not collapsed, the steel frame structure is uniformly erected in an arc shape in the tunnel, one end of the steel pipe supporting structure is inserted into the arch-covered structure, the other end of the steel pipe supporting structure extends into the other part which is not collapsed, the steel pipe supporting structure is fixed on the steel frame structure, and concrete is filled between the steel frame structure and the collapsed cavity surface.

3. The device for reinforcing collapse treatment of preliminary support of road tunnel according to claim 2, wherein the surface of the steel pipe support structure is provided with a plurality of through holes.

4. The device for reinforcing collapse treatment of preliminary support of road tunnel according to claim 2, wherein the steel pipe supporting structures are uniformly distributed on the steel frame structure in a fan shape.

5. The device for reinforcing collapse treatment of preliminary support of road tunnel according to claim 2, wherein every two adjacent steel pipe supporting structures are arranged in a vertically staggered manner.

6. The construction method of the reinforcing device for the collapse treatment of the preliminary support of the road tunnel according to any one of claims 1 to 5, comprising the steps of:

s1: chiseling primary support falling spray concrete for a primary support slight deformation section, resetting a cartridge anchor rod and hanging a net for spray concrete;

s2: aiming at the primary support cracking section, a multi-arch steel frame is adopted for hard support to prevent the primary support collapse section from further traction and damage, and a small grouting guide pipe is synchronously adopted for radial consolidation grouting to keep the stability of surrounding rocks;

s3: the primary support steel frame distortion failure section carries out roof truss-by-roof truss replacement treatment after the primary support is subjected to grouting consolidation stabilization aiming at the position closest to the collapse section;

s4: the method comprises the steps of treating a primary support collapse section, firstly carrying out hole slag back pressure stacking to prevent further traction damage of the collapse part, spraying concrete to seal a hole slag surface, then embedding a pumping pipe, backfilling a collapse cavity by C20 concrete, and then applying long-distance follow-up large pipe shed advance support;

s5: after the advance support is completed, circularly performing annular cutting reserved core soil excavation support in a circulating manner, solidifying loose collapsed slag bodies by adopting a small grouting guide pipe while performing excavation support, and gradually performing downward guide and core soil excavation support after stabilization;

s6: and lining construction is carried out by adopting high-grade secondary lining concrete and reinforcing steel bars, so that a stable and reliable permanent lining structure is formed.

7. The construction method of the device for reinforcing the collapse of the primary support of the road tunnel according to claim 6, wherein in the step S1, an excavation trolley is used as a treatment platform, the primary support cracked shotcrete is chiseled by an air pick, the chiseling process ensures that the primary support surface is smooth and flat, the cracked part is ensured to be completely separated from the concrete, anchor rods with phi 22 cartridges and with the length of 3.5m are arranged again, the distance between the anchor rods is 1.2m multiplied by 1.2m, phi 8 steel meshes are hung on the surface of the shotcrete, the distance between the meshes is 20cm multiplied by 20cm, the end parts of the anchor rods are fixed, and the concrete is sprayed again by C25.

8. The construction method of the reinforcing device for the collapse treatment of the preliminary support of the road tunnel according to claim 6, wherein the step S2 comprises the steps of:

s201: hard supporting by a double-arch steel frame;

s202: radially consolidating the surrounding rock and grouting by the guide pipe;

the step S201 includes:

firstly, I20b steel supports are adopted at a distance of 60cm to carry out rigid support so as to prevent primary support collapse and instability;

secondly, sealing gaps between the double-arch steel frames and the primary support by adopting C25 sprayed concrete;

thirdly, after the multiple arches are installed, phi 22 steel bars are used as longitudinal connecting bars to connect adjacent arch frames together, so that the arch frames form a whole;

and fourthly, adding phi 42 small guide pipes with the length of 4.5m as steel frame locking feet, wherein the locking feet are positioned at the arch waists and the arch feet on two sides of the steel frame, 2 small guide pipes are arranged at each position, and the welding between the small guide pipes and the steel frame is strengthened.

9. The construction method of the reinforcing device for the collapse treatment of the preliminary support of the road tunnel according to claim 6, wherein the step S3 comprises the steps of:

s301: after the primary support distortion failure section is treated stably, an operation platform is provided for later construction by backfilling the hole slag, primary supports on two sides are reversely pressed to prevent the primary supports from unstably collapsing, and the lower slag body is continuously turned forwards along with the propulsion of arch changing to circularly reciprocate;

s302: performing arch change in sequence from an upper step to a lower step, chiseling concrete sprayed on two sides of a steel frame by adopting a hydraulic breaking hammer, chiseling a section of steel support, and mounting a section of steel support, wherein the chiseling width of a first steel frame is slightly wider than that of the steel support; when the second truss is changed, the chiseling width is the designed width between the first truss and the second truss, and the subsequent arch changing modes such as the third truss and the fourth truss are consistent with the second truss.

10. The construction method of the reinforcing device for the collapse treatment of the preliminary support of the road tunnel according to claim 6, wherein the step S4 comprises the steps of:

s401: after the collapsed cavity surrounding rock is stabilized, firstly carrying out hole slag back pressure stacking to prevent the collapsed part from further traction and damage, and sealing the hole slag surface by adopting C25 sprayed concrete;

s402: pre-burying a pumping pipe and backfilling a collapsed cavity by C20 concrete, wherein the total backfilling height is not less than 5m above the vault so as to ensure the safety of later excavation and a cavity structure;

s403, supporting a long-distance advanced pipe-following pipe shed;

s404: after the advance support is solidified, digging again for support at the collapse section of the primary support, sealing the tunnel face of the loose slag body in each cycle by C25 sprayed concrete, grouting by a phi 42 radial small conduit to solidify the loose slag body, and reserving core soil by annular cutting one by one.

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