Grouting reinforcement and transboundary anchoring method for tunnel crossing loose and broken fault zone

Abstract

The invention discloses a grouting reinforcement and transboundary anchoring method for a tunnel crossing a loose and broken fault zone, and belongs to the technical field of tunnel supporting. According to the method, a loose and broken fault zone is divided into relatively complete rock masses on the two sides and a broken fault zone in the middle; grouting is conducted in the middle broken fault zone through the first guide pipe; grouting is conducted on the interface of the middle broken fault zone and the complete surrounding rock on the side away from the tunnel face through a second guide pipe; a plurality of evenly-distributed drill holes are constructed in the rock mass in front of the tunnel face, and a flexible anchor cable is arranged in each drill hole; the first guide pipe and the second guide pipe are used for improving the physical and mechanical properties of the loose and broken fault zone, the self-bearing capacity of the loose and broken fault zone is effectively exerted, the flexible anchor cable penetrates through the loose and broken fault zone and is anchored into complete surrounding rock, and the flexible anchor cable is anchored into the loose and broken fault zone. Diastrophism of a fault zone can be prevented, and therefore the purpose of cross-boundary anchoring is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel support, and in particular to a grouting reinforcement and cross-boundary anchoring method for a tunnel passing through a loose and broken fault zone. Background Art

[0002] As an important part of the highway network, mountain tunnels often encounter unfavorable geological conditions such as weak and broken surrounding rocks, fault fracture zones, and unconformity contact surfaces during construction, which can easily cause engineering disasters such as landslides. At present, the application of advanced support and pre-reinforcement measures, including advanced small guide tubes, advanced anchors, and advanced pipe sheds, has to some extent solved the adverse effects of adverse geological conditions.

[0003] During the construction of mountain tunnels, it is often necessary to cross loose and broken fault zones with a width of more than 10m. Traditional advance support and pre-reinforcement measures cannot effectively control the stability of such a large range of rock mass. The diffusion radius of the slurry injected by the advance small pipe is small, and the reinforcement effect is not ideal. The anchoring area of ​​the advance anchor rod is limited because it does not penetrate into the complete surrounding rock, so the range of action is limited. The construction of the advance pipe shed is also limited by space. Therefore, the above measures are taken, and the stability problem of the gravel in the loose and broken fault zone is not fundamentally solved. There is still a risk of landslide during the construction process, which in turn affects the construction progress. At the same time, there are major safety hazards. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art and to provide a method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone, which can effectively improve the integrity and stability of the loose and broken fault zone, ensure construction progress, and reduce safety risks.

[0005] The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone provided by the present invention comprises the following steps: obtaining the bandwidth and inclination of the loose and broken fault zone through geological survey, dividing the loose and broken fault zone into relatively complete rock masses on both sides and a broken fault zone in the middle;

[0006] Inserting a plurality of first conduits into the rock mass in front of the tunnel face, wherein the insertion ends of the plurality of first conduits are located in the middle broken fault zone, and injecting grout into the middle broken fault zone through the first conduits;

[0007] Insert multiple second conduits in the rock mass in front of the tunnel face, the length of the second conduits being greater than that of the first conduits, and inject grout into the interface between the middle broken fault zone and the intact surrounding rock on the side away from the tunnel face through the second conduits, the second conduits being arranged between two adjacent first conduits, forming a grouting anchoring mode in which the first conduits and the second conduits are arranged at intervals;

[0008] A plurality of evenly distributed boreholes are constructed in the rock mass in front of the tunnel face, each borehole passes through the broken fault zone in the middle from the tunnel face and enters into the intact surrounding rock on the side of the loose broken fault zone away from the tunnel face, each borehole is built with a flexible anchor cable, the length of which is greater than the length of the second guide tube; the flexible anchor cable is anchored at one end of the borehole passing through the broken fault zone in the middle by means of rotary grouting.

[0009] As a preferred embodiment, the first conduit has a diameter of Φ40 mm to Φ55 mm and a length of 3 m to 5 m. The multiple first conduits are arranged in a plum blossom shape with an annular spacing of 0.3 to 0.5 m, an external insertion angle of 10 to 15°, and a grouting pressure of 1 to 2 MPa.

[0010] Grouting holes are set on the pipe wall near the front end of the first pipe, with a hole diameter of 6 to 8 mm and a hole spacing of 15 cm. The front end is processed into a cone shape. Grouting in the first pipe is used to reinforce the broken rock mass in front of the face and control its stability.

[0011] As a preferred embodiment, the second conduit has a diameter of Φ40mm to Φ55mm and a length of 5m to 10m. Multiple second conduits are arranged in a plum blossom shape with an annular spacing of 0.3 to 0.5m, an external insertion angle of 10 to 15°, and a grouting pressure of 1 to 2MPa.

[0012] As a preferred embodiment, a grouting hole is provided on the wall of the second conduit near the front end, with a hole diameter of 6-8 mm and a hole spacing of 15 cm, and the front end of the first conduit is processed into a cone.

[0013] The second conduit reinforces the broken rock mass above the tunnel face and improves the anti-slip capacity at the interface between intact and broken surrounding rock.

[0014] As a preferred embodiment, the length of the second conduit needs to be calculated according to the width and inclination of the loose fractured fault zone, so that the end of the second conduit passes through the middle fractured fault zone and reaches the interface position with the complete surrounding rock on the side away from the tunnel face.

[0015] As a preferred embodiment, the first conduit and the second conduit are both steel pipes.

[0016] As a preferred embodiment, the first conduit and the second conduit are arranged at intervals within a range of 120° on the tunnel vault.

[0017] As a preferred embodiment, the flexible anchor cable is made of steel strands, and the total length is the sum of the exposed length, the length of crossing the loose broken fault zone and the length of the anchoring section anchored in the complete surrounding rock, forming a cross-boundary anchoring.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: after geological survey, the present invention divides the loose and broken fault zone into relatively complete rock masses on both sides and a broken fault zone in the middle, and injects grout into the broken fault zone in the middle through the first conduit; injects grout into the interface between the broken fault zone in the middle and the complete surrounding rock on the side away from the tunnel face through the second conduit, and the end of the flexible anchor cable crosses the broken fault zone in the middle and is anchored in the complete surrounding rock on the side away from the tunnel face through drilling and grouting. The present invention can improve the mechanical properties of the rock mass and improve the stability of the rock mass in front of the tunnel face by grouting with the first and second conduits; grouting at the interface through the second conduit can form a self-bearing structure to stabilize the loose and broken rock mass above the tunnel face; the flexible anchor cable passes through the loose and broken fault zone and is anchored in the complete surrounding rock, which can prevent the fault zone from moving, thereby achieving the goal of cross-border anchoring, and can fundamentally solve the problem of gravel stability in the loose and broken fault zone, and realize safe construction across the loose and broken fault zone with a width of more than 10m. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0020] Figure 2 This is a distribution diagram of the tunnel face structure according to an embodiment of the present invention.

[0021] Description of reference numerals:

[0022] 1. First conduit, 2. Second conduit, 3. Flexible anchor cable. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0024] Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with ordinary skills in the field to which the present disclosure belongs. "First", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of "including" or "comprising" cover the elements or objects listed after "including" or "comprising" and their equivalents, and do not exclude other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone provided by the present invention comprises the following steps: obtaining the bandwidth and inclination of the loose and broken fault zone through geological survey, dividing the loose and broken fault zone into relatively complete rock masses on both sides and a broken fault zone in the middle;

[0026] Inserting a plurality of first conduits 1 into the rock mass in front of the tunnel face, the insertion ends of the plurality of first conduits 1 are located in the middle broken fault zone, and grouting is injected into the middle broken fault zone through the first conduits 1;

[0027] Insert multiple second conduits 2 in the rock mass in front of the tunnel face, wherein the length of the second conduits 2 is greater than that of the first conduits 1, and inject grout into the interface between the middle broken fault zone and the intact surrounding rock on the side away from the tunnel face through the second conduits 2. The second conduits 2 are arranged between two adjacent first conduits 1, forming a grouting anchoring mode in which the first conduits 1 and the second conduits 2 are arranged at intervals.

[0028] A plurality of evenly distributed boreholes are constructed in the rock mass in front of the face, each borehole passes through the broken fault zone in the middle from the face and enters into the intact surrounding rock on the side of the loose broken fault zone away from the face, each borehole is built with a flexible anchor cable 3, the length of the flexible anchor cable 3 is greater than the length of the second guide tube 2; the flexible anchor cable 3 is anchored at one end of the borehole passing through the broken fault zone in the middle by means of rotary grouting.

[0029] As a preferred embodiment, the first conduit 1 has a diameter of Φ40mm~Φ55mm and a length of 3m~5m. Multiple first conduits 1 are arranged in a plum blossom shape with an annular spacing of 0.3~0.5m, an external insertion angle of 10~15°, a grouting pressure of 1~2MPa, and a grouting hole is set at the front of the first conduit 1 with a hole diameter of 6~8mm and a hole spacing of 15cm. The front end is processed into a cone. Grouting of the first conduit 1 is used to reinforce the broken rock mass in front of the tunnel face and control its stability.

[0030] As another preferred embodiment, the second conduit 1 has a diameter of Φ40mm~Φ55mm and a length of 5m~10m. Multiple second conduits 2 are arranged in a plum blossom shape with an annular spacing of 0.3~0.5m, an external insertion angle of 10~15°, a grouting pressure of 1~2MPa, and a grouting hole with a hole diameter of 6~8mm and a hole spacing of 15cm. The front end is processed into a cone. The second conduit 2 reinforces the broken rock mass above the tunnel face and improves the anti-slip ability at the interface between the intact and broken surrounding rock.

[0031] As another preferred embodiment, the first conduit 1 and the second conduit 2 are arranged at intervals within a range of 120° on the tunnel vault.

[0032] As another preferred embodiment, the flexible anchor cable 3 is made of steel strands, and the total length is the sum of the exposed length, the length of crossing the loose broken fault zone and the length of the anchoring section anchored in the complete surrounding rock, forming a cross-boundary anchoring.

[0033] In the construction of a tunnel crossing a loose and broken fault zone, the two sides of the fault zone are defined as relatively intact rock masses, and the middle is a broken fault zone. In order to enhance the stability of the rock mass in front of the tunnel face, cement slurry is injected using a first conduit to improve the mechanical properties of the rock mass. For the loose and broken rock mass above the face, a second conduit is set, and the length of the second conduit is sufficient to reach the interface between the broken fault zone in the middle and the intact rock mass on the side away from the face, and cement slurry is injected through the second conduit to form a self-supporting structure near the interface between the broken fault zone in the middle and the intact rock mass on the side away from the face, thereby improving the physical and mechanical properties of the rock mass. In addition, in order to suppress the slippage of the fault zone and form a self-supporting structure, flexible anchor cables are used. These flexible anchor cables pass through the loose and broken fault zone and are anchored into the intact surrounding rock to prevent the dislocation of the loose and broken fault zone, thereby achieving the goal of cross-border anchoring. The present invention improves the stability of the rock mass through the grouting technology of the first conduit (short conduit) and the second conduit (long conduit) and the flexible anchor cables to ensure the safety and reliability of tunnel construction.

[0034] The first conduit used in this embodiment uses ordinary steel pipes in the range of Φ40mm to Φ55mm to meet the needs of different projects. The length is between 3m and 5m, and can be flexibly adjusted according to actual conditions to ensure that the first conduit can reach the required grouting depth. Multiple first conduits are divided into multiple groups, each of which is arranged in a plum blossom shape. Among the multiple first conduits arranged in a plum blossom shape, the circumferential spacing is controlled at 0.3m to 0.5m, which helps to be evenly arranged in front of the face to improve the uniformity of grouting. The external insertion angle is set between 10° and 15° to reduce the resistance of passing through the rock mass, so that the first conduit can pass through the stratum more smoothly. The grouting pressure is controlled at 1MPa to 2MPa to ensure that the cement slurry can fully penetrate and fill the rock mass cracks, thereby enhancing the overall stability of the rock mass. The design of the grouting hole adopts a plum blossom shape, with a hole diameter of 6mm to 8mm and a hole spacing of 15cm. The front end of the first conduit is tapered, which helps to pass through the rock formation more smoothly. The last 100cm of the tail is not drilled to form a grouting stop section to avoid excessive grouting and ensure that the grouting effect can achieve the expected effect.

[0035] Furthermore, the length of the second conduit needs to be calculated based on the width and inclination of the loose broken fault zone. The length of the second conduit is preferably to cross the middle broken fault zone and reach the interface position with the intact surrounding rock on the side away from the tunnel face, and reach the position of the intact-broken surrounding rock interface. Other parameters are the same as the first conduit. The purpose of the second conduit is to reinforce the broken rock mass above the tunnel face, improve the mechanical properties of the interface between the middle broken fault zone and the intact surrounding rock on the side away from the tunnel face, prevent slippage, and enhance the stability of the entire interface area.

[0036] Furthermore, the first conduit and the second conduit are arranged within 120° of the tunnel vault and arranged in a plum blossom-shaped interval. The flexible anchor cable is made of steel strands, and the total length is the sum of the exposed length, the length of the fault zone crossed and the length of the anchor section anchored in the complete surrounding rock, forming a cross-border anchor to prevent the fault zone from slipping.

[0037] Figure 1 A structural schematic diagram of a preferred embodiment of the present invention is shown.

[0038] Grouting reinforcement and cross-boundary anchoring method for tunnels crossing loose and broken fault zones Before tunnel construction, a detailed geological survey is first carried out, with special attention paid to the geological characteristics of the loose and broken fault zone, including bandwidth and inclination. At the same time, the loose and broken fault zone is divided into relatively intact rock masses on both sides and a broken fault zone in the middle.

[0039] The first conduit is a common steel pipe with a diameter between Φ40mm and Φ55mm and a length between 3m and 5m, and is processed according to the design requirements. The first conduit is arranged within 120° of the tunnel vault in a plum blossom pattern to ensure uniform spacing. Grouting is performed using the first conduit, and the grouting pressure is adjusted between 1MPa and 2MPa to ensure that the cement slurry fully penetrates and fills the rock cracks and improves the mechanical properties of the rock mass. According to the real-time monitoring results, the layout and grouting parameters of the first conduit are adjusted to ensure that the construction effect meets the design requirements.

[0040] The length of the second conduit is calculated according to the width and inclination of the broken zone to ensure that it can reach the interface between the middle broken fault zone and the intact surrounding rock on the side away from the face. The second conduit is arranged in a plum blossom shape within 120° of the tunnel vault to ensure full coverage. The second conduit is used for grouting. This embodiment adopts a plum blossom arrangement to form a self-bearing structure and improve the physical and mechanical properties. After the second conduit is arranged, a borehole is constructed, and a flexible anchor cable is installed in the borehole. One end of the flexible anchor cable passes through the middle broken fault zone and anchors into the intact surrounding rock to form a cross-border anchor to prevent the dislocation of the fault zone. The grouting pipes used in this embodiment are all ordinary steel pipes, which are easy to process and low in cost; the flexible anchor cables used in this embodiment are simple to construct and occupy a small space. The use of long and short conduits improves the physical and mechanical properties of the loose broken fault zone and effectively exerts the self-bearing capacity of the loose broken fault zone.

[0041] Figure 2 This is a distribution diagram of the tunnel face structure of an embodiment.

[0042] Real-time monitoring is required during the construction process, including the grouting effect, the fixing of the conduit and the flexible anchor cable, etc. The layout of the conduit and the grouting parameters are adjusted according to the monitoring results to ensure the construction effect and the stability of the rock mass at the tunnel face ahead.

[0043] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone, characterized in that: The following steps are involved: After geological survey, the loose and broken fault zone is divided into relatively intact rock masses on both sides and a broken fault zone in the middle; Inserting a plurality of first conduits into the rock mass in front of the tunnel face, wherein the insertion ends of the plurality of first conduits are located in the middle broken fault zone, and injecting grout into the middle broken fault zone through the first conduits; Insert multiple second conduits in the rock mass in front of the tunnel face, the length of the second conduits being greater than that of the first conduits, and inject grout into the interface between the middle broken fault zone and the intact surrounding rock on the side away from the tunnel face through the second conduits, the second conduits being arranged between two adjacent first conduits, forming a grouting anchoring mode in which the first conduits and the second conduits are arranged at intervals; A plurality of evenly distributed boreholes are constructed in the rock mass in front of the face, each borehole passes through the broken fault zone in the middle from the face into the intact rock mass on the side of the broken fault zone in the middle away from the face, each borehole is built with a flexible anchor cable, the length of which is greater than the length of the second guide tube; the flexible anchor cable is anchored at one end of the borehole passing through the broken fault zone in the middle by means of drilling grouting.

2. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The first conduit has a diameter of Φ40mm to Φ55mm and a length of 3m to 5m. Multiple first conduits are arranged in a plum blossom shape with an annular spacing of 0.3m to 0.5m, an external insertion angle of 10° to 15°, and a grouting pressure of 1MPa to 2MPa.

3. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 2, characterized in that: Grouting holes are arranged on the conduit wall near the front end of the first conduit, with a hole diameter of 6-8 mm and a hole spacing of 15 cm. The front end of the first conduit is processed into a cone.

4. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The second conduit has a diameter of Φ40mm to Φ55mm and a length of 5m to 10m. Multiple second conduits are arranged in a plum blossom shape with an annular spacing of 0.3m to 0.5m, an external insertion angle of 10° to 15°, and a grouting pressure of 1MPa to 2MPa.

5. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: Grouting holes are arranged on the conduit wall near the front end of the second conduit, with a hole diameter of 6mm to 8mm and a hole spacing of 15cm. The front end of the second conduit is processed into a cone.

6. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The length of the second conduit needs to be calculated according to the width and inclination of the loose fractured fault zone, so that the end of the second conduit passes through the middle fractured fault zone and reaches the interface between the middle fractured fault zone and the intact rock mass on the side away from the tunnel face.

7. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The first conduit and the second conduit are both steel pipes.

8. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The first conduit and the second conduit are arranged at intervals within a range of 120° of the tunnel vault.

9. The method for grouting reinforcement and cross-boundary anchoring of a tunnel passing through a loose and broken fault zone as claimed in claim 1, characterized in that: The flexible anchor cable is made of steel strands, and its total length is the sum of the exposed length, the length of crossing the loose broken fault zone and the length of the anchoring section anchored in the complete surrounding rock, so as to form cross-boundary anchoring.

Images