A method for reinforcing the interior of a super-large hidden karst cave near a tunnel

Abstract

This invention discloses a method for reinforcing a large, concealed karst cave near a tunnel. The method includes: S1, drilling a hole leading to the karst cave on the tunnel structure near the cave, and installing a reinforcing component through the hole to form a reinforced structure supporting the rock and soil above the cave; S2, after the anchoring end of the reinforcing component enters the cave, adjusting the structure to ensure the anchoring end is in close contact with the cave wall, and filling with protective material to seal the gap between the anchoring end and the wall; S3, reinforcing the gap between the reinforcing component and the drill hole, and installing a monitoring device to monitor the stress state of the reinforcing component to ensure the stability of the reinforced structure during tunnel operation. This method for reinforcing a large, concealed karst cave near a tunnel further enhances the friction between the claw-shaped component and the cave wall, significantly improves the anti-slip capability of the anchoring end, and ensures the long-term stability of the supporting structure.

Description

Technical Field

[0001] This invention relates to the fields of tunnel engineering and soil and rock reinforcement technology, specifically to a method for reinforcing an ultra-large hidden karst cave near a tunnel. Background Technology

[0002] In the field of tunnel construction and operation, the complexity of the geological environment is one of the important factors affecting the safety and stability of tunnel projects. Influenced by regional climate and groundwater, karst caves often form inside mountains and underground, with concealed karst caves being particularly common. Concealed karst caves refer to cavities or karst landforms buried beneath the surface, usually formed by the long-term erosion of groundwater. These karst caves have high permeability and large spaces, potentially posing a threat to the construction and subsequent operation of tunnel projects.

[0003] Existing advanced geological forecasting technologies have limitations in identifying and locating hidden karst caves, particularly those outside the tunnel cross-section, making comprehensive detection and treatment difficult. Due to this inability to detect all caves, after tunnel completion and opening to traffic, heavy rainfall during the rainy season, or the effects of train vibrations and groundwater erosion, can lead to loosening, spalling, and even collapse of the cave's inner rock and soil. These changes affect the integrity of the rock mass, adversely impacting the long-term operational safety of the tunnel. Currently, treatment measures for karst caves mainly include backfilling, grouting, and reinforced support. During tunnel construction, backfilling with excavated material or simultaneous grouting is commonly used. However, when the tunnel is already built and the karst cave is large, these traditional methods face significant difficulties and high costs. Furthermore, these methods may not completely solve the stability problems of karst caves during tunnel operation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for reinforcing the interior of a large, concealed karst cave near a tunnel, thereby solving the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for reinforcing an ultra-large concealed karst cave near a tunnel, the method comprising:

[0006] S1. Drill holes leading to the karst cave on the structure of the tunnel near the karst cave, and install reinforcing components through the drill holes to form a reinforcing structure for supporting the rock and soil on the top surface of the karst cave;

[0007] S2. After the anchoring end of the reinforced component enters the karst cave, the anchoring end is made to fit tightly against the karst cave wall through structural adjustment, and protective material is filled to seal the gap between the anchoring end and the rock wall.

[0008] S3. Reinforce the gap between the reinforcement component and the borehole, and install a monitoring device to monitor the stress state of the reinforcement component to ensure the stability of the reinforcement structure during tunnel operation.

[0009] Preferably, the anchoring end includes a claw-shaped component with multiple openable branches. Each branch is equipped with a spring to control the claw-shaped component to change from a closed state to an open state and to fit tightly against the cave wall.

[0010] Preferably, the claw-shaped component is provided with a waterproof, corrosion-resistant and highly elastic protective membrane on its exterior. When the claw-shaped component is opened, the protective membrane completely seals the gaps between each branch and the cave wall.

[0011] Preferably, the reinforcement treatment includes filling the gap between the reinforcement component and the borehole by grouting, and the grouting material is a grout with anti-permeability and anti-corrosion properties.

[0012] Preferably, the grouting is completed through a pre-installed grouting pipe, the exposed part of which is connected to the drilling position, and the grouting port is sealed after grouting is completed.

[0013] Preferably, the monitoring device includes a stress monitoring sensor installed on the reinforced component, used to collect the stress data of the reinforced component in real time and transmit the data to the monitoring system for analysis.

[0014] Preferably, the direction and angle of the drilling are determined based on the location of the karst cave using geological survey data before construction, to ensure that the reinforcement components can effectively support the rock and soil on the top surface of the karst cave.

[0015] Preferably, when the claw-shaped component at the anchoring end is in the open state, the opening angle of each branch is adjusted by the elastic force of the spring to adapt to different shapes of the cave wall.

[0016] Preferably, each branch surface of the claw-shaped component is provided with an anti-slip toothed structure to increase the contact stability between the claw-shaped component and the cave wall.

[0017] Preferably, the protective film is made of a high-molecular polymer material, which has high strength and durability and can resist long-term erosion by groundwater.

[0018] As can be seen from the above technical solution, the present invention has the following beneficial effects:

[0019] The reinforcement method for a super-large hidden karst cave near the tunnel, through scientific and reasonable reinforcement construction steps, improved the overall stability of the karst cave area and provided an important guarantee for the safe operation of the tunnel. By using spring-controlled branches to open and tightly adhere to the karst cave wall, a stable support structure is formed. This not only increases the contact area between the anchor end and the karst cave wall but also improves the reliability of the support effect. A waterproof, corrosion-resistant, and highly elastic protective membrane, when open, completely seals the gap between the anchor end and the rock wall, effectively preventing leakage of grouting material and enhancing the durability of the anchor end. Suitable for complex underground environments, the method further improves the overall strength and deformation resistance of the reinforced structure by filling the gap between the reinforced component and the borehole using a grout with anti-seepage and anti-corrosion properties, meeting long-term operational needs. Grouting is carried out through grouting pipes, facilitating precise control of the flow direction and amount of grouting material during construction. After grouting, the grouting port is sealed to further prevent material loss or environmental pollution. Monitoring devices collect data in real time. The stress data of the anchoring components, analyzed through a monitoring system, provides a basis for long-term condition monitoring and maintenance of the karst cave area. This helps to identify potential problems early and take countermeasures. The design of the drilling direction and angle based on geological exploration data ensures that the reinforcement components can fully cover the support requirements of the karst cave roof rock and soil, improving the construction accuracy and effectiveness of the reinforcement structure. By adjusting the opening angle of the claw-shaped component branches with springs, it can adapt to different karst cave rock wall shapes, enhancing the adaptability of the support system and providing a reliable technical solution for construction under complex geological conditions. By setting anti-slip toothed structures on the surface of the claw-shaped components, the friction between the claw-shaped components and the karst cave rock wall is further enhanced, significantly improving the anti-slip capability of the anchoring end and ensuring the long-term stability of the support structure. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention;

[0021] Figure 2 This is a diagram showing the arrangement of the anchor cable support structure of the present invention between the tunnel and the karst cave;

[0022] Figure 3 This is a schematic diagram of the claw-shaped component of the anchor cable of the present invention;

[0023] Figure 4 This is another schematic diagram of the claw-shaped component of the anchor cable of the present invention;

[0024] Figure 5 This is a schematic diagram of the anchor cable of the present invention.

[0025] In the diagram: 1. Claw-shaped component; 2. Spring; 3. Protective membrane; 4. Grouting pipe. Detailed Implementation

[0026] 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.

[0027] like Figures 1-5 As shown, a method for reinforcing a super-large hidden karst cave near a tunnel is described, the method comprising:

[0028] S1. Drill holes leading to the karst cave on the structure of the tunnel near the karst cave, and install reinforcing components through the drill holes to form a reinforcing structure for supporting the rock and soil on the top surface of the karst cave;

[0029] S2. After the anchoring end of the reinforced component enters the karst cave, the anchoring end is made to fit tightly against the karst cave wall through structural adjustment, and protective material is filled to seal the gap between the anchoring end and the rock wall.

[0030] S3. Reinforce the gap between the reinforcement component and the borehole, and install a monitoring device to monitor the stress state of the reinforcement component to ensure the stability of the reinforcement structure during tunnel operation.

[0031] In this embodiment, drilling allows the reinforcing components to act directly on the rock and soil above the cave, transferring external forces to the stable rock wall. This disperses and reduces stress concentration at the cave top, preventing collapse of the rock and soil. The anchoring ends are tightly fitted to the cave wall and filled with protective material to ensure sealing and stability at the connection. Gap treatment between the reinforcing components and the borehole further improves the overall shear and tensile strength. Real-time monitoring provides long-term assurance of the structure's stability after construction. The reinforced structure significantly enhances the support capacity of the rock and soil above the cave, preventing risks caused by geological instability in the tunnel area. Sealing and gap reinforcement effectively prevent external factors from affecting the reinforced structure, such as groundwater seepage and chemical erosion. The real-time monitoring system ensures the structural stability of the tunnel during long-term operation, enabling timely detection and handling of potential problems.

[0032] In one possible implementation, the anchoring end includes a claw-shaped component 1 with multiple openable branches. Each branch is equipped with a spring 2 to control the claw-shaped component 1 from a closed state to an open state, ensuring close contact with the cave wall. Through the elastic force of the spring mechanism, the branches of the claw-shaped component automatically open after entering the cave, ensuring a tight fit with the cave wall. The spring provides independent adjustment force for each branch, allowing it to flexibly adapt to different cave wall shapes and avoiding instability caused by shape differences during construction. This provides a flexible anchoring method, ensuring the stability of the reinforced component. The spring-opening design is highly adaptable, suitable for complex cave shapes, reducing the workload of secondary adjustments. It increases the contact area between the anchoring end and the cave wall, enhancing the overall support effect.

[0033] In one possible implementation, the claw-shaped component 1 is externally provided with a waterproof, corrosion-resistant, and highly elastic protective membrane 3. When the claw-shaped component 1 opens, the protective membrane 3 completely seals the gaps between each branch and the cave wall. The protective membrane 3 expands synchronously with the opening of the claw-shaped component, and its high elasticity ensures that it can cover all gaps between the branches and the rock wall, thus forming a continuous sealing layer. This sealing layer can prevent long-term damage to the reinforced structure from groundwater and corrosive substances. The sealing structure effectively prevents the influence of external environmental factors on the reinforced component, improving durability. It provides additional protection against wear or displacement that may result from direct contact between the anchoring end and the rock wall. It enhances the overall environmental adaptability of the reinforced structure and extends its service life.

[0034] In one possible implementation, the reinforcement treatment includes filling the gap between the reinforcing member and the borehole by grouting, using a grouting material with impermeability and corrosion resistance. By injecting a grout with a specific ratio into the gap between the reinforcing member and the borehole, the grout can diffuse and fill the narrow void, eventually solidifying to form a filling layer with high strength and stability. The impermeability ensures that the filling layer effectively blocks groundwater infiltration, while the corrosion resistance protects the reinforcing member and the borehole wall from chemical erosion. This improves the connection strength and stability between the reinforcing member and the borehole, reducing the risk of displacement or shear failure. The use of an impermeable and corrosion-resistant grout enhances the durability of the entire structure, particularly its adaptability to humid or corrosive environments. Construction efficiency is optimized; the grouting process is simple and easy to implement, suitable for complex geological conditions on site.

[0035] In one possible implementation, grouting is accomplished via a pre-installed grouting pipe 4, the exposed portion of which connects to the borehole location, and the grouting port is sealed after grouting is completed. The grouting pipe 4 serves as a grout delivery channel, and its exposed portion facilitates connection to grouting equipment. During construction, by controlling the grouting volume and pressure, the grout is evenly distributed within the gap between the reinforced component and the borehole. Sealing the grouting port after grouting prevents grout backflow or intrusion of external contaminants. The use of the grouting pipe facilitates construction operations and improves grouting efficiency and accuracy. Sealing the grouting port further enhances the integrity of the reinforcement treatment, preventing the impact of subsequent environmental changes on the reinforced structure. The flexible grouting pipe design can adapt to boreholes of different lengths and shapes.

[0036] In one possible implementation, the monitoring device includes a stress monitoring sensor mounted on the reinforced component to collect stress data of the component in real time and transmit the data to the monitoring system for analysis. The stress monitoring sensor uses precision measurement technology to sense stress changes borne by the reinforced component in real time and transmits this data to the monitoring system as signals. The monitoring system can record, analyze, and display the data, helping construction personnel to promptly grasp the stress state of the reinforced component and assess the stability and safety of the structure. Real-time monitoring can effectively provide early warning of potential structural problems, offering data support for maintenance and repair. Through long-term monitoring, a large amount of construction data can be accumulated, providing experience and parameter basis for similar projects. Data-driven management improves the accuracy and reliability of monitoring and reduces the workload of manual inspections.

[0037] In one possible implementation, the direction and angle of the borehole are determined based on geological survey data obtained before construction, according to the location of the karst cave, to ensure that the reinforced components can effectively support the soil and rock mass above the cave. Geological survey methods, such as ground-penetrating radar or drilling sampling, are used to obtain data on the spatial location, shape, and soil and rock properties of the karst cave. The direction and angle of the borehole are designed based on this data to precisely penetrate the area above the cave that needs support, ensuring the uniformity and stability of the reinforced components under stress. Drilling design guided by geological data improves the targeting and effectiveness of construction, reducing the possibility of ineffective drilling. Precise borehole positioning maximizes the supporting effect of the reinforced structure, helping to extend its service life. It also reduces the need for secondary drilling or rework due to construction errors, improving project efficiency.

[0038] In one possible implementation, when the claw-shaped component 1 at the anchoring end is in the open state, the opening angle of each branch is adjusted by the elastic force of the spring 2 to adapt to different shapes of the cave wall. The branches of the claw-shaped component 1 adjust their opening angles according to the shape of the cave wall, ensuring that each branch can make close contact with the wall. The elastic coefficient of the spring is optimized based on the rock wall strength and anchoring requirements, ensuring both branch flexibility and support stability. The adaptive adjustment function significantly improves the anchoring effect of the claw-shaped component in complex terrain, reducing support defects caused by irregular rock wall shapes. The spring adjustment provides a stable opening force, allowing the claw-shaped component to maintain reliable fit in various environments. This design simplifies the anchoring construction process, eliminating the need for additional manual adjustment of branch angles and improving construction efficiency.

[0039] In one possible implementation, each branch surface of the claw-shaped component 1 is provided with an anti-slip serrated structure to increase the contact stability between the claw-shaped component 1 and the cave wall. The anti-slip serrated structure on the branch surface of the claw-shaped component 1 increases friction through physical embedding when in contact with the rock wall, thereby improving the stability of the anchorage. The shape and arrangement of the serrations are designed according to the characteristics of the rock wall material to maximize the anchorage effect and reduce the risk of slippage. The anti-slip serrations enhance the shear resistance of the anchorage end, improving the overall deformation resistance of the structure. This design further reduces the risk of the claw-shaped component detaching from the rock wall due to uneven stress, improving construction safety. It also reduces reliance on external fixing measures, optimizing the construction process and cost.

[0040] In one possible implementation, the protective membrane 3 is made of a high-molecular polymer material, possessing high strength and durability, and capable of resisting long-term groundwater erosion. The protective membrane 3, made of a high-molecular polymer material, provides excellent mechanical strength and durability through its polymer chain structure. This material is treated for waterproofing and chemical resistance, effectively resisting corrosive ions and microbial attack in groundwater, ensuring the stability and integrity of the protective membrane in complex underground environments over extended periods. The high-molecular polymer material enhances the service life of the protective membrane, reducing replacement and maintenance costs. Its resistance to groundwater erosion ensures long-term effective sealing between the anchoring end and the rock wall. It provides an additional physical protective layer, preventing mechanical damage to the anchoring end from the external environment.

[0041] Work process: Step 1: First, remove the existing secondary lining structure of the tunnel. Find a good angle on the sidewall and arch bottom of the existing tunnel near the cave and carry out drilling operations until the top of the cave below. Drive anchor cables through the drilling to form an anchor cable support structure between the existing tunnel and the top of the cave to support and reinforce the rock wall of the cave top.

[0042] Step 2: After the anchor cable is driven into the borehole and the anchor end passes through the borehole, tighten the anchor cable rear end fastening head so that the springs 2 on each branch of the claw-shaped component 1 at the anchor end are stressed. The claw-shaped component (1) changes from the closed state when it is pierced to the open state and is tightly attached to the cave wall. The protective film attached to the claw-shaped component 1 tightly wraps the gap between each branch and the rock wall as the claw-shaped component 1 opens.

[0043] Step 3: Grout the gap between the anchor cable and the borehole. After grouting and reinforcement, leave a space after the steel shim 5 at the anchor cable fastening end to install the anchor cable stress monitoring device to monitor the stress state of the subsequent anchor cable. Finally, re-apply the secondary lining.

[0044] like Figure 2 As shown, there is a super-large karst cave near the tunnel. The overall shape of the cave cavity is higher on the left and lower on the right (in the direction of the tunnel's movement), and narrower at the top and wider at the bottom. The reinforcement structure for the super-large hidden karst cave is mainly an anchor cable support structure, located between the tunnel sidewall and arch bottom and the cave ceiling. Drilling operations are carried out from the existing tunnel sidewall and arch bottom downwards to the cave ceiling, and anchor cables are driven in.

[0045] like Figure 3 and Figure 4 As shown, the anchoring end of the anchor cable is a claw-shaped component 1, and each branch of the claw-shaped component 1 has a spring 2. The claw-shaped component 1 is in a closed state when not under stress. When the anchoring section of the anchor cable passes through the borehole, the anchoring head is tightened to force the spring 2. The spring 2 controls the branches to spread out and adhere tightly to the cave wall to form a relatively stable support structure.

[0046] like Figure 3 and Figure 4 As shown, the claw-shaped component 1 has a protective membrane 3 on its outside, which is made of a material with waterproof, corrosion-resistant, and highly elastic properties. When the claw-shaped component 1 opens, it completely wraps around each of the opened branches and adheres tightly to the cave wall. The protective membrane 3 completely seals the gap between the anchoring end and the cave wall, preventing leakage of subsequent grouting liquid.

[0047] like Figure 5 As shown, the anchor cable support structure includes an anchor cable anchoring end (claw-shaped component), an anchor cable free section, and an anchor cable fastening end (steel washer and nut). The grouting treatment is carried out through a PE grouting pipe 4. After the anchor cable is installed, the PE pipe is inserted as a grouting pipe, with about 10cm of the grouting pipe 4 exposed. The steel washer 5 is installed, and the nut 6 is locked before grout is injected.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reinforcing a large, concealed karst cave near a tunnel, characterized in that, The method includes: S1. Drill holes leading to the karst cave on the structure of the tunnel near the karst cave, and install reinforcing components through the drill holes to form a reinforcing structure for supporting the rock and soil on the top surface of the karst cave; S2. After the anchoring end of the reinforced component enters the karst cave, the anchoring end is made to fit tightly against the karst cave wall through structural adjustment, and protective material is filled to seal the gap between the anchoring end and the rock wall. S3. Reinforce the gap between the reinforcement component and the borehole, and install a monitoring device to monitor the stress state of the reinforcement component to ensure the stability of the reinforcement structure during tunnel operation. The anchoring end includes a claw-shaped component (1), which has multiple openable branches. Each branch is provided with a spring (2) to control the claw-shaped component (1) to change from a closed state to an open state and to fit tightly against the cave wall. The claw-shaped component (1) is provided with a waterproof, corrosion-resistant and highly elastic protective membrane (3) on the outside. When the claw-shaped component (1) is opened, the protective membrane (3) completely seals the gap between each branch and the cave wall. The reinforcement treatment includes filling the gap between the reinforcement component and the borehole by grouting, and the grouting material is a grout with anti-seepage and anti-corrosion properties; The monitoring device includes a stress monitoring sensor installed on the reinforced component, which is used to collect the stress data of the reinforced component in real time and transmit the data to the monitoring system for analysis; Each branch surface of the claw-shaped component (1) is provided with an anti-slip toothed structure to increase the contact stability between the claw-shaped component (1) and the cave wall.

2. The method for reinforcing a super-large hidden karst cave near a tunnel according to claim 1, characterized in that: The grouting is completed through a pre-installed grouting pipe (4), the exposed part of which is connected to the drilling position, and the grouting port is sealed after the grouting is completed.

3. The method for reinforcing a large, concealed karst cave near a tunnel according to claim 1, characterized in that: The direction and angle of the borehole are determined based on geological survey data before construction, according to the location of the karst cave, to ensure that the reinforcement components can effectively support the rock and soil on the top surface of the karst cave.

4. The method for reinforcing a large, concealed karst cave near a tunnel according to claim 1, characterized in that: When the claw-shaped component (1) at the anchoring end is in the open state, the opening angle of each branch is adjusted by the elastic force of the spring (2) to adapt to different shapes of the cave wall.

5. The method for reinforcing a large, concealed karst cave near a tunnel according to claim 1, characterized in that: The protective membrane (3) is made of polymer materials, has high strength and durability, and can resist long-term erosion by groundwater.

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