A method for treating convergence deformation of initial support of side wall of tunnel under high ground stress surrounding rock

Abstract

The application discloses a tunnel side wall primary support convergence deformation treatment method under high ground stress surrounding rock and relates to the technical field of tunnel reinforcement. The method comprises the following steps: S1, performing gravel backfilling on the convergence deformation area, performing compaction treatment on the gravel backfilled in the convergence deformation area, and forming core soil, wherein the core soil is used for forming a transverse pressure on the convergence deformation area to resist the deformation of the surrounding rock of the convergence deformation area; S2, performing concrete spraying on the tunnel face and the convergence deformation area to seal the tunnel face and the convergence deformation area; S3, installing self-advancing anchor rods in the convergence deformation area, and performing grouting and solidification on the self-advancing anchor rods to stabilize the surrounding rock of the convergence deformation area; and S4, replacing the steel arch frames in the convergence deformation area, and timely installing and grouting lock foot anchor rods to reinforce the lock foot anchor rods and reduce the subsequent deformation of the convergence deformation area and the risk of construction, so that a safe and reliable tunnel side wall primary support convergence deformation treatment method is provided.

Description

Technical Field

[0001] This invention relates to the field of tunnel reinforcement technology, and in particular to a method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock. Background Technology

[0002] During tunnel construction, uncertain bias pressure, deformation, and instability can occur due to topographic and geological factors (such as high ground stress, groundwater, or the tunnel's own expansion properties). In these cases, the load acting on the tunnel surrounding rock is asymmetrical, easily causing shear failure in the soft rock on the biased side, inducing the surrounding rock to evolve from its original stable state to deformation-bound failure. Anchoring and grouting are the most effective engineering methods for controlling cracking and deformation of the surrounding rock in biased tunnels. Given the characteristics of biased rock strata, stress is rapidly released after the rock strata are exposed at the tunnel face, and the deformation rate is fast in the initial stage of exposure. Therefore, early control of the expansion of the loosened zone of the surrounding rock to maintain the integrity of the original rock as much as possible is crucial.

[0003] In tunnels with high ground stress and fractured surrounding rock, the arch and sides are prone to damage. When the surrounding rock on the biased side undergoes encroachment deformation, it leads to the initial support convergence deformation, requiring arch replacement. The encroaching surrounding rock of the initial support is manually removed. The principle of removing the encroaching surrounding rock is to minimize the disturbance of the surrounding rock and avoid large-scale operations to prevent collapse and roof fall accidents. Summary of the Invention

[0004] The purpose of this invention is to provide a method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock, so as to solve the problems existing in the prior art, reduce the subsequent deformation in the convergence deformation area, reduce the construction risk, and provide a safe and reliable method for treating the initial support convergence deformation of tunnel sidewalls.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for treating the initial support convergence deformation of a tunnel sidewall under high ground stress surrounding rock, comprising the following steps:

[0007] S1. Backfill the convergent deformation area with sand and gravel, and compact the backfilled sand and gravel within the convergent deformation area to form core soil. The core soil is used to form a lateral pressure on the convergent deformation area to resist the deformation of the surrounding rock in the convergent deformation area.

[0008] S2. Seal the tunnel face and the convergence deformation area with sprayed concrete;

[0009] S3. Install self-drilling anchor bolts in the convergent deformation area and grout and solidify the self-drilling anchor bolts to stabilize the surrounding rock in the convergent deformation area;

[0010] S4. Replace the steel arch frames in the convergence deformation area according to the principle of "short advance, strong support, quick closure, and frequent measurement". When a certain number of steel arch frames are replaced, install anchor bolts and grout them in time to reinforce them.

[0011] Preferably, the backfill length and backfill height of the sand and gravel in step S1 are determined by the convergence deformation region or based on the convergence of the convergence deformation region, and the backfill width of the sand and gravel is the initial support net width of the tunnel.

[0012] Preferably, step S2 further includes sealing the backfilled sand and gravel shotcrete, and the thickness of the shotcrete is 10cm.

[0013] Preferably, step S3 further includes determining the length of the self-advancing anchor bolt: conducting advanced radar detection on the geological conditions of the surrounding rock behind the convergence deformation area to determine the depth of the hard rock layer, and then drilling anchor bolt holes to determine the length of the self-advancing anchor bolt.

[0014] Preferably, the self-drilling anchor bolts of the straight leg section of the steel arch frame should be drilled from the core soil, with a drilling angle of 30° to 50° downward horizontally, a longitudinal spacing of 1.5m, and a transverse spacing of 1m; the circumferential spacing at the waist and crown of the steel arch frame is 150mm.

[0015] Preferably, S4 also includes replacing the steel arch frame every two spans of excavation, cutting off the exposed length of the self-advancing anchor bolts, and promptly sealing it with shotcrete after the arch replacement is completed. After the initial support concrete reaches 70% of the design strength, the next two spans are excavated, and the above steps are repeated until the steel arch frame replacement is completed in the entire convergence deformation area.

[0016] Preferably, the anchor rod is made of Φ20 steel bar, with a downward angle of 15° to 35°, and is inserted into the hard rock layer; the anchor rod is arranged on the left and right sides of the straight leg part of the steel arch frame, and is also provided on the upper and lower sides; the anchor rods on both sides of the straight leg part of the steel arch frame at the same location are fixedly connected to the steel arch frame by steel plates.

[0017] Preferably, the steel plate is welded and fixed to the steel arch frame, and the steel plate is provided with through holes on both sides of the steel arch frame. The end of the locking foot anchor rod extending out is provided with a threaded end, and the threaded end of the locking foot anchor rod extending out of the through hole is connected to the threaded end of the locking foot anchor rod by a nut to fix the locking foot anchor rod to the steel plate.

[0018] Preferably, the diameter of the mounting hole for the anchor bolt should be 25mm larger than the diameter of the anchor bolt itself. The anchor bolt locking foot is centrally located in the mounting hole and sealed at the opening of the mounting hole with a grout stopper.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] This invention provides a method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress. The method involves backfilling the convergence deformation area with sand and gravel and compacting it to form core soil, creating lateral pressure to resist the deformation of the surrounding rock. Shotcrete is then applied to seal the convergence deformation area to prevent further convergence deformation of the tunnel profile, ensuring the safety of subsequent construction. Self-drilling anchors are then installed and grouted to stabilize the surrounding rock. Finally, the steel arch frame is gradually replaced, and locking anchors are installed and grouted for reinforcement. This method reduces subsequent deformation in the convergence deformation area, lowers construction risks, and provides a safe and reliable solution for treating the initial support convergence deformation of tunnel sidewalls under high ground stress. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The outline surface of the tunnel before the initial support convergence deformation;

[0023] Figure 2 The outline surface of the tunnel after the initial support convergence deformation;

[0024] Figure 3 Cross-sectional view of the convergent deformation area after backfilling with sand and gravel;

[0025] Figure 4 This is a top view of the tunnel after backfilling with sand and gravel.

[0026] Figure 5 This is a layout diagram for self-propelled anchor bolts;

[0027] Figure 6 , Figure 7 and Figure 8 Schematic diagram for replacing the steel arch frame;

[0028] Figure 9 This is a cross-sectional view of the convergent deformation area after the steel arch frame replacement is completed.

[0029] Figure 10 This is a front view of the anchor bolt.

[0030] In the diagram: 1. Core soil; 2. Tunnel face; 3. Convergence deformation zone; 4. Shotcrete; 5. Self-advancing anchor; 6. Steel arch; 7. Locking anchor; 8. Steel plate; 9. Through hole; 10. Tunnel initial support. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The purpose of this invention is to provide a method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock, so as to solve the problems existing in the prior art, reduce the subsequent deformation in the convergence deformation area, reduce the construction risk, and provide a safe and reliable method for treating the initial support convergence deformation of tunnel sidewalls.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] This invention provides a method for treating the initial support convergence deformation of a tunnel sidewall under high ground stress surrounding rock; comprising the following steps:

[0035] S1: By backfilling and compacting sand and gravel in the convergence deformation zone 3 of the tunnel's initial support 10, a core soil 1 is constructed, such as... Figure 3 The biased surrounding rock in the convergence deformation zone 3 is subjected to a lateral pressure, which temporarily resists the deformation of the surrounding rock in the collapsed cavity. Shotcrete 4 is used to seal the tunnel face 2, core soil 1 and the exposed rock surface of the collapsed cavity to prevent further convergence deformation of the tunnel outline. Only after fully demonstrating the stability of the surrounding rock in the sidewall convergence deformation zone 3 can the next construction procedure be carried out.

[0036] S2. Construction of self-propelled anchor bolts 5

[0037] (1) In this treatment method, the self-advancing anchor 5 includes an anchor body, a nut, an arched pad, a grout stopper, an alloy drill bit, and an anchor connecting sleeve. The nut can concentrate the stress of the surrounding rock to the pad, the arched pad can withstand greater stress of the surrounding rock, the grout stopper keeps the grout injection at a certain pressure to fully fill the voids in the surrounding rock, and the alloy drill bit has extremely strong penetrating power, enabling the anchor to penetrate various types of rocks.

[0038] (2) Mark the hole positions according to the design requirements, such as Figure 5Once everything is ready, align the anchor drill bit with the marked hole position and begin drilling. Drilling should be carried out with more rotations and less impact to avoid drilling debris clogging the water holes of the rock drill.

[0039] (3) After drilling to the designed depth, clean the hole with water or high-pressure air. After confirming that it is unobstructed, remove the drill rod connecting sleeve and keep the exposed length of the anchor rod 10-15cm.

[0040] (4) Use the hole cap assembly to drive the grout stop plug into the hole about 30cm through the exposed end of the self-advancing anchor rod 5.

[0041] (5) If the self-drilling anchor bolt 5 needs to be lengthened, use the anchor bolt connecting sleeve to connect the driven anchor bolt body to the anchor bolt body to be connected, and then continue drilling until the designed depth.

[0042] (6) After all self-propelled anchor bolts 5 are installed, grouting operations shall begin. To ensure uninterrupted grouting, the condition of the grouting pump and the completeness of accessories shall be carefully checked before grouting. The raw materials for grout preparation shall also be checked for completeness and quality to avoid affecting subsequent grouting operations. 425 ordinary Portland cement shall be used for grouting. The cement mortar shall contain a mixture of cement, bentonite, and water in a mass ratio of 1047kg:52kg:628kg:21kg. The grouting pressure shall be controlled at 10 Bar (0.3-1.0 MPa).

[0043] (7) Quickly connect the anchor rod, grouting hose and grouting pump with quick connectors.

[0044] (8) Start the grouting pump to grout until the grout overflows from the periphery of the hole or the pressure gauge reaches the design pressure value. Each anchor rod must be completed in one go.

[0045] (9) After a self-propelled anchor rod 5 is completed, quickly remove the grouting hose and anchor rod joint, clean it and move it to the next anchor rod. If the pump stop time is long, the residual grout in the grouting pipe should be drained before grouting the next self-propelled anchor rod 5.

[0046] S3. Replace steel arch frame 6

[0047] (1) Excavation can only begin after all the above-mentioned anchor bolts have been installed, grouted and reached the design strength. The entire excavation and arch replacement operation should be carried out in accordance with the principle of "short advance, strong support, quick closure and frequent measurement". The arch should be replaced once every two arches. The exposed length of the self-advancing anchor bolt 5 should be cut off. After the arch replacement is completed, spray concrete 4 should be applied in time to seal it. The next two arches should be excavated after the initial support concrete strength reaches 70% of the design strength.

[0048] (2) Repeat the above steps until the entire convergent deformation area 3 steel arch 6 is replaced.

[0049] S4. Installation and grouting of anchor bolt 7

[0050] According to S3, such as Figure 7 When replacing 6 steel arch frames 6, anchor bolts 7 should be installed in a timely manner. The anchor bolt holes should be marked out according to the design requirements and drilled using a pneumatic rock drill. To ensure that the steel frame has better self-supporting capacity, the drilling angle should be 15° to 35° with the horizontal direction, the drilling diameter should be 15mm larger than the anchor bolt diameter, the anchor bolt drilling depth should be 10cm greater than the anchor bolt design length, and the anchor bolt depth error should be less than ±50cm.

[0051] (2) Use high-pressure air to clean the hole, and check the hole diameter, hole depth and hole inclination after cleaning.

[0052] (3) Ordinary Portland cement of grade PO42.5 is used for grouting. The cement mortar contains cement, bentonite, water and a mixture with a mass ratio of 1047kg:52kg:628kg:21kg. The grouting pressure is controlled at 10 Bar (0.3-1.0 MPa). The grouting pipe is inserted to the bottom of the hole 50-100mm. After the grouting starts, the grouting pipe is repeatedly pushed to the bottom of the hole so that the cement mortar squeezes the excess water in the hole out of the hole. The grouting pipe is slowly and evenly pulled out as the mortar is injected. The grouting pressure is less than 0.4 MPa.

[0053] (4) Insert the anchor bolt 7 according to the design requirements. If no mortar overflows from the hole during the installation process, grout should be added. The allowable deviation of the anchor bolt hole depth is ±50mm. Figure 10 The anchor rods 7 are arranged on the left and right sides of the straight leg section of the steel arch frame 6, and then connected with 2cm thick steel plates 8. The anchor rods 7 passing through the through holes 9 are tightened and fixed with nuts.

[0054] S6: As Figure 8 Excavation of the working face 2 can only begin after all the anchor bolts 7 have been installed. The excavation advance should not exceed 1.2m. Excavation should be carried out by blasting, and blasting is prohibited to avoid secondary disturbance to the surrounding rock.

[0055] S7: Timely follow-up on the construction of the invert arch and secondary lining, and quickly close the initial support arch frame into a ring to enhance the support force of the tunnel arch and greatly reduce construction safety hazards.

[0056] Strengthen process monitoring and measurement, and analyze and provide timely feedback on measurement results to guide treatment construction and formulate emergency response strategies.

[0057] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for treating the initial support convergence deformation of a tunnel sidewall under high ground stress surrounding rock, characterized in that: Includes the following steps: S1. Backfill the convergent deformation area with sand and gravel, and compact the backfilled sand and gravel within the convergent deformation area to form core soil. The core soil is used to form a lateral pressure on the convergent deformation area to resist the deformation of the surrounding rock in the convergent deformation area. S2. Shotcrete is sprayed to seal the tunnel face and the convergence deformation area; S3. Install self-drilling anchor bolts in the convergent deformation area and grout and solidify the self-drilling anchor bolts to stabilize the surrounding rock in the convergent deformation area; S4. Replace the steel arch frames in the convergence deformation area according to the principle of "short advance, strong support, quick closure, and frequent measurement". When a certain number of steel arch frames are replaced, install anchor bolts and grout them in time to reinforce them. S4 also includes replacing the steel arch frame every two spans of excavation, cutting off the exposed length of the self-advancing anchor rods, and promptly sealing it with shotcrete after the arch replacement is completed. The next two spans are excavated only after the initial support concrete reaches 70% of its design strength. This process is repeated until the entire convergence deformation area of ​​the steel arch frame is replaced. The locking anchor rods are made of Φ20 steel bars, with a downward angle of 15°~35°, and are embedded deep into the hard rock layer. The locking anchor rods are arranged on both the left and right sides of the straight leg portion of the steel arch frame, and are also present on the upper and lower sides. The locking anchor rods on both sides of the straight leg portion of the steel arch frame at the same location are fixedly connected to the steel arch frame by steel plates. The steel plates are welded to the steel arch frame, and through holes are provided on both sides of the steel arch frame. The protruding end of the locking anchor rod is provided with a threaded end, which is threadedly connected to the threaded end of the locking anchor rod protruding from the through hole by a nut to fix the locking anchor rod to the steel plate.

2. The method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock according to claim 1, characterized in that: The backfill length and backfill height of the sand and gravel in step S1 are determined by the convergence deformation zone or based on the convergence of the convergence deformation zone, and the backfill width of the sand and gravel is the initial support net width of the tunnel.

3. The method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock according to claim 1, characterized in that: Step S2 also includes sealing the backfilled sand and gravel shotcrete, and the thickness of the shotcrete is 10cm.

4. The method for treating the initial support convergence deformation of tunnel sidewalls under high-stress surrounding rock according to claim 1, characterized in that: Step S3 also includes determining the length of the self-advancing anchor bolt: conducting advanced radar detection on the geological conditions of the surrounding rock behind the convergence deformation area to determine the depth of the hard rock layer, and then drilling anchor bolt holes to determine the length of the self-advancing anchor bolt.

5. The method for treating the initial support convergence deformation of tunnel sidewalls under high ground stress surrounding rock according to claim 4, characterized in that: The self-drilling anchor bolts of the straight leg section of the steel arch frame should be drilled from the core soil at a horizontal downward angle of 30°~50°, with a longitudinal spacing of 1.5m and a transverse spacing of 1m; the circumferential spacing at the waist and crown of the steel arch frame is 150mm.

6. The method for treating the initial support convergence deformation of tunnel sidewalls under high-stress surrounding rock according to claim 1, characterized in that: The diameter of the mounting hole for the anchor bolt should be 25mm larger than the diameter of the anchor bolt. The anchor bolt is centered in the mounting hole and sealed with a grout stop plug at the opening of the mounting hole.

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