Construction process and reinforcing system of pressure-relief and re-grouting composite support reinforcing system for soft rock tunnel

Abstract

The application relates to a construction process and a reinforcing system of a yielding and re-grouting composite support reinforcing system for a soft rock tunnel. In the reinforcing system, a yieldable and slippable grouting anchor rod is a primary lining, is punched into the surrounding rock, a BFRP mesh is closely arranged on the surrounding rock, a prefabricated modular bag is arranged below the BFRP mesh to support the surrounding rock, a support section arch is below the prefabricated modular bag to hold the whole system, and lining concrete is a secondary lining which is poured around the support section arch to support the whole system. The application realizes that the soft rock tunnel can orderly release deformation in the large deformation stage, avoids that the support rigidity is too large and the soft rock extrusion deformation is too large, and can timely strengthen the structural system after the deformation tends to be stable, so that safety, economy and construction convenience are considered.

Description

Technical Field

[0001] This invention relates to a construction process and reinforcement system for a pressure relief and re-grouting composite support system for soft rock tunnels, belonging to the field of tunnel and underground engineering technology, especially for the initial support and subsequent reinforcement technology of tunnels in fractured zones, expansive soft rock or high ground stress soft rock environments. Background Technology

[0002] my country's infrastructure construction, including transportation, water conservancy, and mining, is rapidly advancing into deeper and more complex geological areas. As a result, tunnel projects frequently need to traverse soft surrounding rock strata such as mudstone, carbonaceous shale, phyllite, and argillaceous sandstone. These soft rocks have low strength, well-developed joints, and significant rheological properties. After tunnel excavation, the stress in the surrounding rock is rapidly released, making them highly susceptible to continuous compression and large deformation.

[0003] Currently, soft rock tunnel engineering typically employs a combination of shotcrete, steel arches, and anchor bolts / cables, grouting, etc., primarily focusing on "strong support," which uses high-strength steel arches, large-tonnage prestressed anchor bolts, and thick layers of shotcrete to resist surrounding rock pressure. Under normal soft rock conditions, this type of support can control surrounding rock deformation to a certain extent. However, under conditions of high ground stress, strong rheology, and large deformation, the mismatch between traditional rigid support and the mechanical response of the surrounding rock becomes prominent. In particular, traditional anchor bolts are mostly rigid connections, and when the deformation of the surrounding rock exceeds the ultimate elongation rate of the anchor bolt material (usually 15%~20%), the anchor bolt will break or the support plate will fail, leading to the instantaneous collapse of the support system. To alleviate the problem of easy failure of rigid support, the industry has proposed various "pressure-yielding" anchor bolts. By adding pressure-yielding components, sliding mechanisms, or damping components, a certain relative displacement between the anchor bolt and the surrounding rock is allowed to release deformation pressure. However, existing pressure relief support has obvious limitations. For example, the pressure relief process is often sudden and uncontrollable, the support force fluctuates violently, and it is easy to cause secondary disturbance to the surrounding rock. In addition, conventional anchor bolts are mostly rigid connections, which reduces the degree of bonding with the surrounding rock and makes it difficult to restore a high-strength support state in the later stage.

[0004] In summary, existing soft rock tunnels lack a novel support technology that can achieve controllable pressure relief, adapt to large deformations of the surrounding rock, maintain stable support bearing capacity throughout the entire process, work collaboratively with the surrounding rock, and facilitate engineering implementation. Therefore, developing a soft rock tunnel support and reinforcement technology with a reasonable structure, stable mechanical properties, and the ability to deform collaboratively and bear continuous load is of significant engineering value and practical importance for solving the problem of controlling large deformations in high-stress soft rock tunnels and ensuring the long-term safety and stability of tunnel projects. Summary of the Invention

[0005] This invention provides a construction process and reinforcement system for a pressure relief and re-grouting composite support system for soft rock tunnels. It enables the orderly release of deformation during the large deformation stage of soft rock tunnels, avoiding excessive support stiffness and excessive soft rock compression deformation. After the deformation stabilizes, it can also strengthen the structural system in a timely manner, thus taking into account safety, economy and construction convenience.

[0006] The technical solution adopted by this invention to solve its technical problem is: A construction process for a pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels includes the following steps: Step S1: Excavate the soft rock tunnel to form a cavity inside the soft rock tunnel. Place several BFRP mesh sheets on the surface of the surrounding rock of the cavity. Embed the supporting profile arch frame into the soft rock tunnel cavity and form a space between the supporting profile arch frame and the several BFRP mesh sheets. Step S2: The yieldable sliding grouting anchor is driven into the surrounding rock from the inner cavity of the soft rock tunnel, embedding the inner core rod into the surrounding rock, and the deformation degree of the surrounding rock is monitored in real time by the force sensor installed at the end of the yieldable sliding grouting anchor. Step S3: Grouting is performed from the exposed end of the yieldable sliding grouting anchor into the surrounding rock to initially reinforce the soft rock tunnel. Step S4: Fill the prefabricated modular bag with gas. The gas is compressible and absorbs the initial convergence deformation of the surrounding rock. Then, place it in the space formed between the supporting profile arch and several BFRP mesh sheets, and fix it to the supporting profile arch with bolts. Displacement gauges are distributed on the surface of the prefabricated modular bag to monitor and obtain the convergence deformation of the surrounding rock in real time. Step S5: Continue to set up the inner formwork for the lining at the inner wall of the supporting profile arch frame. After the inner formwork is completed, pour the lining concrete and remove the inner formwork after curing to the standard age. Step S6: Monitor the real-time values ​​of the friction yield sleeve and force sensor of the yieldable sliding grouting anchor. As the soft surrounding rock deforms and slides, the tensile force on the yieldable sliding grouting anchor increases. When the real-time values ​​of the friction yield sleeve and force sensor exceed the preset values, the inner core rod of the yieldable sliding grouting anchor will quantitatively shrink and slide to achieve the purpose of releasing energy inside the surrounding rock and reducing pressure. Step S7: After the inner core rod has shrunk quantitatively, grouting continues from the exposed end of the yieldable sliding grouting anchor rod into the surrounding rock to perform secondary fixation on the soft rock tunnel. Step S8: Continue to monitor the real-time values ​​of the displacement gauge, friction yield sleeve, and force sensor until the convergence deformation tends to stabilize. Then, inject micro-expansion cement-based grout through the grouting port of the prefabricated modular bag to fill and harden the prefabricated modular bag, forming a support layer between the supporting profile arch and several BFRP meshes, thus completing the construction of the entire reinforcement system. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support reinforcement system for soft rock tunnels includes yieldable sliding grouting anchors, prefabricated modular bags, BFRP mesh, supporting profile arches, and lining concrete. The inner core of the yieldable sliding grouting anchor is directly inserted into the surrounding rock. Several BFRP meshes are attached to the surface of the surrounding rock in the soft rock tunnel cavity. The supporting profile arches are erected in the soft rock tunnel cavity. Prefabricated modular bags are set between the inner side of the supporting profile arches and the BFRP meshes. Lining concrete is poured on the outer side of the supporting profile arches.

[0007] Furthermore, the yieldable sliding grouting anchor bolt is used for the initial lining, and is driven into the soft surrounding rock and grouted for fixation after the tunnel excavation is completed; The yieldable sliding grouting anchor bolt includes an outer sleeve, an inner core rod, a limiting ring, a friction yielding sleeve, a force sensor, a check valve, a grouting pipeline, and an exposed end of the yieldable sliding grouting anchor bolt. The inner core rod is fixed inside the outer sleeve by the friction yielding sleeve. A limiting ring is fitted on the end of the outer sleeve near the surrounding rock surface to prevent sliding. The force sensor is located at the end of the inner core rod to measure the tensile stress on the anchor bolt. The exposed end of the yieldable sliding grouting anchor bolt is connected to the grouting equipment through a reserved channel in the support system. The grouting pipeline is located inside the outer sleeve and the inner core rod, and the check valve is located on the grouting pipeline to prevent grout backflow and avoid clogging of the grouting pipeline. The friction yield sleeve and force sensor are connected to the computer via a wireless connection device to transmit monitoring data to the computer. At the same time, the computer can control the gripping force of the friction yield sleeve on the inner core rod to control the amount of contraction and slippage of the inner core rod. Furthermore, the main body of the yieldable sliding grouting anchor is made of basalt fiber reinforced composite material to ensure its sufficient durability and tensile strength; Furthermore, the prefabricated modular bag serves as the second lining support for soft rock surrounding rock, closely attached to the BFRP mesh, and fixed above the supporting profile arch frame by bolts; The prefabricated modular bag has a double-layer structure. The inner liner is made of thermoplastic polyurethane coated high-strength nylon cloth, and the outer liner is made of basalt fiber reinforced composite material. The inner liner ensures the airtightness and basic mechanical properties of the prefabricated modular bag, while the outer liner enhances the bag's stress performance and provides protection. The prefabricated modular bag has a grouting port and an air outlet, and the grouting port is connected to the grouting equipment through a reserved channel in the support system. The surface of the prefabricated modular bag is equipped with a displacement meter for monitoring the convergence deformation of the soft surrounding rock, and the displacement monitoring data is uploaded to the computer via a wireless connection device. Furthermore, the BFRP mesh is arranged and fixed close to the surrounding rock, and is made by binding basalt fiber reinforced composite reinforcement in a longitudinal and transverse manner. The basalt fiber reinforced composite reinforcement is obtained by pultruding and curing basalt fiber roving after soaking in epoxy resin curing agent. Furthermore, the supporting profile arch frame below the prefabricated modular bag plays an overall supporting role, and is completely wrapped and covered after the lining concrete is poured. The raw material used in the supporting profile arch frame is basalt fiber reinforced composite material, which is obtained by placing basalt fiber untwisted roving into a fixed mold, adding epoxy resin, and then extruding and curing. Furthermore, the lining concrete serves as the final lining support, pouring and encasing the entire supporting profile arch and the exposed surrounding rock surface; The lining concrete is made of high-ductility concrete.

[0008] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art: 1. The construction process of the pressure relief and grouting composite support and reinforcement system for soft rock tunnels provided by the present invention follows the core support principle of first controlling the shape, then reducing pressure, secondary reinforcement and then permanent curing. At the same time, it matches the purpose of temporary support, dynamic adjustment and permanent reinforcement of each support part. The components in the final reinforcement system work together to ensure long-term stability. 2. In the reinforcement system formed by the construction process of the pressure-yielding and re-grouting composite support and reinforcement system for soft rock tunnels provided by this invention, the yieldable sliding grouting anchor is a type of yieldable sliding anchor that can release deformation energy to achieve the "pressure yielding" effect, avoiding excessive support stiffness and cracking caused by hard squeezing of the surrounding rock; at the same time, after "pressure yielding", it can be reinforced and strengthened over time (re-grouting) to avoid secondary disturbance to the surrounding rock; and the grouting is more thorough and uniform (controlled by check valve), with no cross-flow, runoff, or backflow of grout; 3. In the reinforcement system formed by the construction process of the pressure-yielding and re-grouting composite support and reinforcement system for soft rock tunnels provided by the present invention, the prefabricated modular bags can be used to absorb the initial convergence deformation of the soft rock surrounding rock to achieve "pressure yielding". After the "pressure yielding" is completed, timely reinforcement is carried out to ensure that the support system can fully bear pressure and the long-term stability of the structure. At the same time, the bags are industrially prefabricated, which is convenient for on-site installation and has excellent mechanical properties and airtightness. 4. In the reinforcement system formed by the construction process of the pressure relief and re-grouting composite support reinforcement system for soft rock tunnels provided by the present invention, the combined support system of the supporting profile arch frame and the lining concrete provides sufficient support resistance while allowing the surrounding rock to undergo a certain amount of plastic deformation, thereby releasing the deformation energy of the surrounding rock; while achieving "pressure relief" support, it ensures that the support system has sufficient support force and durability. Attached Figure Description

[0009] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0010] Figure 1 This is a construction process flow diagram of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels provided by the present invention; Figure 2 This is a three-dimensional structural schematic diagram of a preferred embodiment of the reinforcement system provided by the present invention; Figure 3 This is a schematic diagram of the cross-sectional structure of a preferred embodiment of the reinforcement system provided by the present invention; Figure 4 This is a diagram illustrating the structure and grouting principle of a yieldable sliding grouting anchor in a preferred embodiment of the reinforcement system provided by this invention. Figure 5 This is a schematic diagram of the shrinkage and sliding principle of the inner core rod of the yieldable sliding grouting anchor rod in a preferred embodiment of the reinforcement system provided by the present invention; Figure 6 This is a schematic diagram of the grouting expansion and hardening principle of the prefabricated modular bag in a preferred embodiment of the reinforcement system provided by the present invention; Figure 7 This is a three-dimensional structural diagram of the supporting profile arch frame in a preferred embodiment of the reinforcement system provided by the present invention.

[0011] In the diagram: 1 is a yieldable sliding grouting anchor bolt, 1-1 is the outer sleeve, 1-2 is the inner core rod, 1-3 is the limiting ring, 1-4 is the friction yielding sleeve, 1-5 is the force sensor, 1-6 is the check valve, 1-7 is the grouting pipeline, and 1-8 is the exposed end of the yieldable sliding grouting anchor bolt. 2 represents the prefabricated modular bag; 2-1 represents the inner liner layer; 2-2 represents the outer liner layer; 2-3 represents the grouting port; 2-4 represents the air outlet; and 2-5 represents the displacement gauge. 3 is BFRP mesh, 4 is supporting profile arch frame, 5 is lining concrete, 6 is surrounding rock, 7 is grouting equipment, 8 is wireless connection equipment, and 9 is computer terminal. Detailed Implementation

[0012] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0013] As described in the background section, existing tunnel engineering technologies for soft rock tunnels suffer from common defects such as rigid support being prone to brittle fracture, pressure-yielding support being unstable, and anchoring performance being difficult to sustain. Therefore, soft rock surroundings are highly susceptible to continuous large-scale compression deformation after excavation, leading to the destruction of existing support structures. To address these challenges, this application provides a construction process for a pressure-yielding and re-grouting composite support reinforcement system for soft rock tunnels. The entire construction process progresses through three core stages of soft rock tunnel support: Initially, multi-level collaborative rapid shape control prevents collapse and quickly constrains instantaneous deformation of the soft rock, providing a safe foundation for subsequent procedures; in the middle stage, dynamic pressure yielding releases stress, followed by secondary grouting via anchor bolts to achieve a balance between stress release and support force recovery, avoiding stress concentration that could damage the support system; in the later stage, solidification and reinforcement transforms temporary flexible supports into permanent rigid supports, forming a closed-loop support system that integrates the reinforcement system with the surrounding rock, ensuring long-term stability.

[0014] The following section details the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels, such as... Figure 1 As shown, it includes the following steps: Step S1 involves excavating the soft rock tunnel to create a cavity inside. Several BFRP mesh sheets 3 are then laid on the surface of the surrounding rock 6 within the cavity. A supporting arch frame 4 is embedded into the soft rock tunnel cavity, with space created between the supporting arch frame and the BFRP mesh sheets. The core function of the BFRP mesh sheets is to adhere to the surrounding rock surface, preventing fragments from detaching or falling off. The supporting arch frame provides overall support, while the space between the supporting arch frame and the BFRP mesh sheets allows for subsequent anchor bolt driving and bag installation.

[0015] This application also provides a method for manufacturing BFRP mesh, which is made by binding basalt fiber reinforced composite ribs (BFRP ribs) in a longitudinal and transverse distribution. Preferably, the raw material used for the supporting arch frame is also made of basalt fiber reinforced composite material. The aforementioned basalt fiber reinforced composite ribs (BFRP ribs) are obtained by placing untwisted basalt fiber rovings into a fixed mold, adding epoxy resin, and then extruding and curing them, resulting in excellent mechanical properties and durability.

[0016] Step S2: The yieldable sliding grouting anchor 1 is driven into the surrounding rock from the inner cavity of the soft rock tunnel, the inner core rod 1-2 is embedded in the surrounding rock, and the deformation degree of the surrounding rock is monitored in real time by the force sensor 1-5 installed at the end of the yieldable sliding grouting anchor. Step S3 involves grouting from the exposed end of the yieldable sliding grouting anchor into the surrounding rock to provide initial reinforcement for the soft rock tunnel. The yieldable sliding grouting anchor serves as the initial lining. After the tunnel excavation is completed, the yieldable sliding grouting anchor is driven into the soft rock surrounding rock and then initially fixed by grouting. To ensure that the anchor has sufficient durability and tensile strength, the main body of the yieldable sliding grouting anchor is made of basalt fiber reinforced composite material.

[0017] Meanwhile, yieldable sliding grouting anchors must meet the requirements of yieldable sliding grouting. This application provides preferred options for yieldable sliding grouting anchors. Figure 4 As shown, the yieldable sliding grouting anchor bolt includes an outer sleeve 1-1, an inner core rod, a limiting ring 1-3, a friction yielding sleeve 1-4, a force sensor, a check valve 1-6, a grouting pipeline 1-7, and an exposed end 1-8 of the yieldable sliding grouting anchor bolt. A force sensor is installed at one end of the inner core rod to measure the tensile stress on the anchor bolt. This end is inserted into the surrounding rock. The other end of the inner core rod is coaxially connected to the inside of the outer sleeve through the friction yielding sleeve. A limiting ring is fitted on the end of the outer sleeve near the surrounding rock surface to prevent the outer sleeve from sliding. A through grouting pipeline is set at the central axis position where the inner core rod and the outer sleeve communicate. The grouting pipeline is located at the inlet of the exposed end of the yieldable sliding grouting anchor bolt and is connected to the grouting equipment 7. At the same time, a check valve is installed on the grouting pipeline to prevent grout backflow and avoid clogging of the grouting pipeline. The aforementioned friction yield sleeve and force sensor are connected to the computer terminal 9 via wireless connection device 8, so that the monitoring data can be transmitted to the computer terminal in real time. The computer terminal can control the gripping force of the friction yield sleeve on the inner core rod to control the amount of contraction and slippage of the inner core rod.

[0018] Step S4: The prefabricated modular bag 2 is filled with gas, which is compressible and absorbs the initial convergence deformation of the surrounding rock. It is then placed in the space formed between the supporting arch frame and several BFRP mesh sheets, and fixed to the supporting arch frame with bolts. The prefabricated modular bag, as the second lining support for the soft rock surrounding rock, is tightly attached to the BFRP mesh sheets. Figures 1-2 From a mid-range perspective, the BFRP mesh is located on top of the prefabricated modular bag, which in turn is on top of the supporting arch frame and secured with bolts. The prefabricated modular bag includes an inner liner layer 2-1 and an outer layer 2-2, with the outer layer covering the inner liner. The inner liner is made of thermoplastic polyurethane (TPU) coated high-strength nylon fabric, while the outer layer is made of basalt fiber reinforced composite material (BFRP). The inner liner ensures the airtightness and basic mechanical properties of the prefabricated modular bag, while the outer layer enhances the bag's load-bearing capacity and provides protection. Grouting ports 2-3 and air outlets 2-4 are provided on the prefabricated modular bag, with the grouting ports connected to the grouting equipment via a pre-reserved channel in the reinforcement system.

[0019] Displacement gauges 2-5 are distributed on the surface of the prefabricated modular bag, and are also connected to the computer via wireless connection devices to monitor and obtain the convergence deformation of the surrounding rock in real time.

[0020] Steps S1-S4 above belong to the initial stage of surrounding rock control in the entire construction process. BFRP mesh is the most basic surface protection. Yieldable sliding grouting anchors connect the surface soft rock with the internal stable rock mass. Then, the first grouting is carried out to form an integrated structure of mortar, surrounding rock, and anchor body, achieving effective anchoring. In step S4, air-filled bags are used as temporary supports, which can both conform to the surrounding rock and form flexible supports, providing internal working space for subsequent lining.

[0021] Step S5, as the forming stage of the lining structure, continues to erect the inner formwork of the lining at the inner wall of the supporting profile arch frame. After the inner formwork is completed, lining concrete 5 is poured, and the inner formwork is removed after curing to the standard age. After the lining concrete is poured, it serves as the final lining support, which is the core of the permanent support and the core component for achieving "pressure yielding". It completely wraps and covers the supporting profile arch frame and the prefabricated modular bag, further restricting the deformation of the surrounding rock and providing a rigid bearing foundation for subsequent pressure yielding and secondary grouting operations. The material used for the lining concrete is high ductility concrete (HDC). The advantage of choosing this material is that soft surrounding rock often undergoes significant inward convergence deformation after excavation. The high ductility of HDC allows it to deform in tandem with the surrounding rock without fracturing. While providing sufficient support resistance, it allows the surrounding rock to undergo a certain amount of plastic deformation, thereby releasing the deformation energy of the surrounding rock and further achieving "pressure yielding" support.

[0022] Step S6 involves monitoring the real-time values ​​of the friction yield sleeve and force sensor of the yieldable sliding grouting anchor. As the soft surrounding rock deforms and slides, the tensile force on the yieldable sliding grouting anchor increases. When the real-time values ​​of the friction yield sleeve and force sensor exceed preset values, the inner core rod of the yieldable sliding grouting anchor contracts and slides quantitatively, achieving the purpose of releasing energy and reducing pressure within the surrounding rock. This is a dynamic pressure reduction adjustment stage implemented after the lining concrete has hardened. Through the quantitative contraction of the yieldable sliding grouting anchor, the deformation energy of the soft surrounding rock is released, preventing the support system from being destroyed due to stress concentration. This step cannot be advanced or delayed; otherwise, the support system will fail prematurely due to insufficient rigidity, and the anchor contraction will lead to the collapse of the surrounding rock.

[0023] Step S7: After the inner core rod has shrunk quantitatively, grouting continues from the exposed end of the yieldable sliding grouting anchor rod into the surrounding rock to perform secondary fixation of the soft rock tunnel.

[0024] Further explanation of this step is that the yieldable sliding grouting anchor bolt, as a crucial core component for achieving "pressure relief," provides support after initial reinforcement in step S3. Since this application targets soft surrounding rock, it will continuously deform and slide, thereby increasing the tensile force on the anchor bolt. When the yield force of the friction yield sleeve is reached or the stress value measured by the force sensor exceeds the set value, the inner core rod will quantitatively contract and slide within the outer sleeve to achieve the "pressure relief" effect. Figure 5 As shown in the diagram, the principle is "first bearing, then yielding"; the inner core rod "yields" by contracting and sliding, which releases some of the stress in the surrounding rock. However, if the anchor rod continues to slide, its anchoring effect will decrease. Therefore, in step S7, grouting is performed again using grouting equipment to fix the anchor rod a second time. This second grouting operation prevents the anchor rod from breaking or pulling out due to excessive rigidity during large deformations in soft rock. It can release deformation, delay cracking, and maintain continuous support force.

[0025] Step S8 is the permanent curing reinforcement stage. The real-time values ​​of the displacement gauge, friction yield sleeve, and force sensor continue to be monitored until the convergence deformation stabilizes. Then, micro-expansion cement-based grout is injected through the grouting port of the prefabricated modular bag, causing the prefabricated modular bag to fill and harden. The hardening principle is as follows: Figure 7 As shown, a support layer is formed between the supporting profile arch frame and several BFRP mesh panels, completing the construction of the entire reinforcement system.

[0026] In the initial stage, the prefabricated modular bag is an inflatable flexible support that adapts to the dynamic process of surrounding rock deformation. When the computer monitors that the surrounding rock convergence deformation tends to stabilize, it means that the deformation energy of the surrounding rock has been basically released and the internal stress has basically reached a state of equilibrium. Only then can the bag, surrounding rock, BFRP mesh and supporting profile arch form a permanent rigid support.

[0027] Finally, through the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels provided above, a system is formed. Figures 2-3 The reinforcement system shown features a yieldable sliding grouting anchor with its inner core directly inserted into the surrounding rock. Several BFRP mesh sheets are attached to the surface of the soft rock tunnel cavity. A supporting arch frame is erected in the soft rock tunnel cavity. A prefabricated modular bladder is installed between the inner side of the supporting arch frame and the BFRP mesh sheets. The supporting arch frame supports the entire reinforcement system. Concrete lining is poured on the outer side of the supporting arch frame as a secondary lining, providing the final fixed support for the reinforcement system.

[0028] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0029] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0030] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A construction process for a pressure-relief and re-grouting composite support and reinforcement system for soft rock tunnels, characterized in that: Includes the following steps: Step S1: Excavate the soft rock tunnel, form a cavity inside the soft rock tunnel, lay several BFRP meshes (3) on the surface of the surrounding rock (6) of the inner cavity, embed the supporting profile arch frame (4) into the inner cavity of the soft rock tunnel, and form a space between the supporting profile arch frame and several BFRP meshes. Step S2, the yieldable sliding grouting anchor (1) is driven into the surrounding rock from the inner cavity of the soft rock tunnel, the inner core rod is embedded in the surrounding rock, and the deformation degree of the surrounding rock is monitored in real time by the force sensor installed at the end of the yieldable sliding grouting anchor. Step S3: Grouting is performed from the exposed end of the yieldable sliding grouting anchor into the surrounding rock to initially reinforce the soft rock tunnel. Step S4: Fill the prefabricated modular bag (2) with gas. The gas is compressible and absorbs the initial convergence deformation of the surrounding rock. Then place it in the space formed between the supporting profile arch and several BFRP mesh sheets, and fix it to the supporting profile arch with bolts. Displacement gauges (2-5) are distributed on the surface of the prefabricated modular bag to monitor and obtain the convergence deformation of the surrounding rock in real time. Step S5: Continue to set up the inner formwork for the lining at the inner wall of the supporting profile arch frame. After the inner formwork is completed, pour the lining concrete (5). Remove the inner formwork after curing to the standard age. Step S6: Monitor the real-time values ​​of the friction yield sleeve and force sensor of the yieldable sliding grouting anchor. As the soft surrounding rock deforms and slides, the tensile force on the yieldable sliding grouting anchor increases. When the real-time values ​​of the friction yield sleeve and force sensor exceed the preset values, the inner core rod of the yieldable sliding grouting anchor will quantitatively shrink and slide to achieve the purpose of releasing energy inside the surrounding rock and reducing pressure. Step S7: After the inner core rod has shrunk quantitatively, grouting continues from the exposed end of the yieldable sliding grouting anchor rod into the surrounding rock to perform secondary fixation on the soft rock tunnel. Step S8: Continue to monitor the real-time values ​​of the displacement gauge, friction yield sleeve, and force sensor until the convergence deformation tends to stabilize. Then, inject micro-expansion cement-based grout through the grouting port of the prefabricated modular bag to fill and harden the prefabricated modular bag, forming a support layer between the supporting profile arch and several BFRP meshes, thus completing the construction of the entire reinforcement system.

2. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 1, characterized in that: The structure includes yieldable sliding grouting anchors, prefabricated modular bags, BFRP mesh, supporting profile arches, and lining concrete. The inner core of the yieldable sliding grouting anchor is directly inserted into the surrounding rock. Several BFRP meshes are attached to the surface of the surrounding rock in the soft rock tunnel cavity. The supporting profile arches are erected in the soft rock tunnel cavity. Prefabricated modular bags are set between the inner side of the supporting profile arches and the BFRP meshes. Lining concrete is poured on the outer side of the supporting profile arches.

3. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 2, characterized in that: The yieldable sliding grouting anchor is used for the initial lining. After the tunnel excavation is completed, it is driven into the soft surrounding rock and grouted to fix it. The yieldable sliding grouting anchor bolt includes an outer sleeve (1-1), an inner core rod (1-2), a limiting ring (1-3), a friction yield sleeve (1-4), a force sensor (1-5), a check valve (1-6), a grouting pipeline (1-7), and an exposed end (1-8) of the yieldable sliding grouting anchor bolt. The inner core rod is fixed inside the outer sleeve by the friction yield sleeve. A limiting ring is fitted on the end of the outer sleeve near the surrounding rock surface to prevent sliding. The force sensor is located at the end of the inner core rod to measure the tensile stress on the anchor bolt. The exposed end (1-8) of the yieldable sliding grouting anchor bolt is connected to the grouting equipment through a reserved channel in the support system. The grouting pipeline (1-7) is located inside the outer sleeve and the inner core rod. The check valve (1-6) is located on the grouting pipeline to prevent grout backflow and avoid clogging of the grouting pipeline. The friction yield sleeve and force sensor are connected to a computer via a wireless connection device to transmit monitoring data to the computer. At the same time, the computer can control the gripping force of the friction yield sleeve on the inner core rod to control the amount of contraction and slippage of the inner core rod.

4. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 3, characterized in that: The main body of the yieldable sliding grouting anchor is made of basalt fiber reinforced composite material to ensure its sufficient durability and tensile strength.

5. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 2, characterized in that: The prefabricated modular bag is the second lining support for soft rock surrounding rock, closely attached to the BFRP mesh, and fixed above the supporting profile arch frame by bolts; The prefabricated modular bag has a double-layer structure. The inner liner is made of thermoplastic polyurethane coated high-strength nylon cloth, and the outer liner is made of basalt fiber reinforced composite material. The inner liner ensures the airtightness and basic mechanical properties of the prefabricated modular bag, while the outer liner enhances the bag's stress performance and provides protection. The prefabricated modular bag has a grouting port and an air outlet, and the grouting port is connected to the grouting equipment through a reserved channel in the support system. The surface of the prefabricated modular bag is equipped with a displacement gauge to monitor the convergence deformation of the soft surrounding rock, and the displacement monitoring data is uploaded to the computer via a wireless connection device.

6. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 5, characterized in that: The BFRP mesh is arranged and fixed close to the surrounding rock. It is made by binding basalt fiber reinforced composite reinforcement in both directions. The basalt fiber reinforced composite reinforcement is obtained by pultruding and curing basalt fiber roving after soaking in epoxy resin curing agent.

7. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 2, characterized in that: The supporting profile arch frame is located below the prefabricated modular bag and provides overall support. After the lining concrete is poured, it completely covers and encloses the bag. The raw material used in the supporting profile arch frame is basalt fiber reinforced composite material, which is obtained by placing basalt fiber roving into a fixed mold, adding epoxy resin, and then extruding and curing.

8. The reinforcement system formed by the construction process of the pressure relief and re-grouting composite support and reinforcement system for soft rock tunnels according to claim 2, characterized in that: The lining concrete serves as the final lining support, pouring and enclosing the entire supporting profile arch frame and the exposed surrounding rock surface. The lining concrete is made of high-ductility concrete.

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