Soft rock waterproof layer construction method for tunnel at large deformation section of soft rock

Abstract

The invention discloses a soft rock waterproof layer construction method for a soft rock large-deformation section tunnel, and relates to the technical field of soft rock waterproof layer construction of the soft rock large-deformation section tunnel. The construction method of the soft rock waterproof layer for the tunnel at the large deformation section of the soft rock comprises the steps that a sprayed concrete layer is constructed, a full-ring-shaped steel arch frame is erected, system anchor rods are constructed, concrete is sprayed again after full-length grouting is conducted, and a primary supporting layer containing a grouting reinforcing ring is formed; locking anchor pipe grouting is carried out on the arch springing part to form a local reinforced waterproof bearing body; based on deformation monitoring data, dynamic judgment is carried out, and radial reinforcing grouting is carried out on the obvious deformation part; and after deformation is stable, a waterproof layer is laid, a secondary lining is poured, and a composite waterproof system is formed. The waterproof reliability and the structural durability of the soft rock waterproof layer of the tunnel at the large deformation section of the soft rock can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft rock waterproof layer construction of soft rock large deformation section tunnel, and particularly relates to a soft rock waterproof layer construction method for soft rock large deformation section tunnel. BACKGROUND

[0002] In the practice of soft rock tunnel engineering, the inherent characteristics of low strength, weak self-stability and softening when encountering water of surrounding rock make it prone to sustained large deformation after excavation. Such deformation not only causes cracking of the supporting structure, but also significantly aggravates the risk of water leakage, and in severe cases even induces tunnel collapse accidents, posing a serious challenge to construction safety and structural durability. To address this problem, the engineering community has gradually developed a technical path from single rigid support to flexible support, composite support, and current integrated comprehensive management of "support-grouting-waterproofing". Although the technical system is constantly improving, there are still systematic defects in the existing methods for constructing waterproof layers in soft rock large deformation sections.

[0003] The commonly used "primary support + waterproof board + secondary lining" composite structure first forms a preliminary bearing system by spraying concrete, steel arch and system anchor in the implementation process; after the deformation of the surrounding rock is basically stable, the waterproof board is laid on the inner surface of the primary support and the secondary lining is poured; although some projects add lock foot anchors or anchor pipes in the arch foot area to improve local strength, and take remedial measures such as additional bolting or radial grouting when deformation is abnormal, this phased construction mode exposes deep-seated problems. The waterproof performance of the primary support system is severely insufficient, grouting reinforcement only focuses on the surrounding rock body, and a continuous waterproof bearing layer inside the supporting structure cannot be constructed, resulting in continuous infiltration of groundwater along the construction gap between the sprayed layer and the surrounding rock. Deformation monitoring and reinforcement measures lack scientific quantitative criteria and dynamic response mechanisms, and engineering practice often relies on subjective experience, resulting in reinforcement measures often lagging behind the deformation development process and failing to effectively intervene in the early stages of deformation. The waterproof reinforcement measures at stress concentration points such as the arch foot are isolated and unsystematic, and the local weak links are disconnected from the overall support system, forming a high-probability leakage channel. The connection between the various waterproof procedures is loose, and the primary support, waterproof layer and secondary lining operate independently, and a composite waterproof system that works in coordination cannot be formed, making it difficult for the overall waterproof reliability to meet the complex working condition requirements of soft rock large deformation sections. SUMMARY

[0004] The main purpose of the present application is to provide a soft rock waterproof layer construction method for soft rock large deformation section tunnel, which aims to improve the waterproof reliability and structural durability of the soft rock waterproof layer of soft rock large deformation section tunnel.

[0005] To achieve the above-mentioned purpose, the soft rock waterproof layer construction method for soft rock large deformation section tunnel provided by the present application comprises: applying a shotcrete layer on the tunnel excavation profile, erecting a full-ring steel arch, applying system anchor rods and full-length grouting of the system anchor rods, and then applying a shotcrete layer to the designed thickness to form a primary support layer containing a grouting reinforced ring; applying a lock-foot anchor pipe at the arch foot of the primary support layer and injecting grout into the lock-foot anchor pipe to form a locally reinforced waterproof load-bearing body; monitoring the deformation of the primary support layer, and when the monitoring data meets a preset deformation anomaly criterion, drilling a radial grouting hole in the primary support layer at a significant deformation position and performing supplemental grouting of the radial grouting hole; after the deformation of the primary support layer is stable, laying a waterproof layer on the inner surface of the primary support layer, and pouring a reinforced concrete secondary lining on the inner side of the waterproof layer, so that the primary support layer and the secondary lining jointly form a composite waterproof system.

[0006] In an embodiment, the step of applying a shotcrete layer on the tunnel excavation profile, erecting a full-ring steel arch, applying system anchor rods and full-length grouting of the system anchor rods, and then applying a shotcrete layer to the designed thickness to form a primary support layer containing a grouting reinforced ring includes: immediately after excavation, spraying a first layer of concrete on the tunnel excavation profile to preliminarily close the rock surface; erecting the full-ring steel arch in a full-ring closed manner; installing hollow grouting anchor rods as the system anchor rods at the arch and sidewall positions; injecting cement grout through the hollow channels of the hollow grouting anchor rods, with a grouting pressure of 0.3 MPa to 0.8 MPa, and continuing grouting until grout returns at the orifice; laying a steel mesh on the outer side of the full-ring steel arch and binding and fixing the steel mesh to the full-ring steel arch; performing a second layer of shotcrete work to completely wrap the full-ring steel arch, the steel mesh, and the trays of the hollow grouting anchor rods, forming a dense primary support layer.

[0007] In an embodiment, before the step of injecting cement grout through the hollow channels of the hollow grouting anchor rods, with a grouting pressure of 0.3 MPa to 0.8 MPa, and continuing grouting until grout returns at the orifice, the soft rock waterproof layer construction method for a soft rock large deformation section tunnel further includes: applying an initial pre-tightening force to the hollow grouting anchor rods; wherein the initial pre-tightening force is not less than 60 kN.

[0008] In an embodiment, the step of applying a lock-foot anchor pipe at the arch foot of the primary support layer and injecting grout into the lock-foot anchor pipe to form a locally reinforced waterproof load-bearing body includes: Drilling an inclined borehole at a design position of the arch foot part; Inserting a seamless steel pipe with a slurry overflow hole into the inclined borehole; Connecting a grouting pipe through the seamless steel pipe and injecting cement slurry with a water-cement ratio of 0.35 to 0.4; Stopping grouting when the grouting pressure reaches 1.0 to 2.0 MPa and is stable for not less than 5 minutes.

[0009] In an embodiment, the preset deformation anomaly criterion is that the daily net convergence value is greater than 30 mm, or the cumulative convergence value reaches 70% of the design reserved deformation amount and the deformation rate does not show a downward trend; and the reinforcement grouting adopts cement-sodium silicate double-liquid slurry. The step of drilling a radial grouting hole in the primary support layer at a deformation significant position and performing reinforcement grouting on the radial grouting hole when the monitoring data meets the preset deformation anomaly criterion comprises: Performing the reinforcement grouting through the radial grouting hole with a depth of 3 to 5 meters, and the final grouting pressure is 0.5 to 1.5 MPa.

[0010] In an embodiment, the step of drilling a radial grouting hole in the primary support layer at a deformation significant position and performing reinforcement grouting on the radial grouting hole when the monitoring data meets the preset deformation anomaly criterion further comprises: Drilling first sequence grouting holes at intervals and performing grouting on the first sequence grouting holes; After the initial setting of the slurry in the first sequence grouting holes, drilling second sequence grouting holes in the middle of adjacent first sequence grouting holes and performing grouting on the second sequence grouting holes; wherein the entire grouting process adopts a skip-hole construction method.

[0011] In an embodiment, before the step of forming a primary support layer comprising a grouting reinforced ring by spraying a concrete layer on a tunnel excavation contour surface, erecting a full-ring steel arch, spraying a concrete layer on the system anchor and performing full-length grouting on the system anchor, and then spraying a concrete layer to a design thickness, the soft rock waterproof layer construction method for a soft rock large deformation section tunnel further comprises: Before the working face is excavated, spraying an advanced middle pipe shed along the tunnel arch and performing grouting on the advanced middle pipe shed to form a pre-reinforced arch shell outside the excavation contour.

[0012] In an embodiment, after the primary support layer is deformed stably, the step of laying a waterproof layer on the inner surface of the primary support layer and pouring a reinforced concrete secondary lining on the inner side of the waterproof layer so that the primary support layer and the secondary lining jointly constitute a composite waterproof system comprises: After the average value of the clearance convergence rate of the primary support layer for seven consecutive days is less than 2 mm per day, and there is no new obvious water leakage point on the surface of the primary support layer, the inner surface of the primary support layer is subjected to flatness treatment and the water leakage point is plugged or drained before the waterproof layer is laid.

[0013] In an embodiment, the waterproof layer is a high polymer waterproof board. After the primary support layer is deformed stably, a waterproof layer is laid on the inner surface of the primary support layer, and a reinforced concrete secondary lining is poured on the inner side of the waterproof layer, so that the primary support layer and the secondary lining jointly constitute a composite waterproof system, and the step further comprises: The high polymer waterproof board is fixed to the inner surface of the primary support layer by using a hot melt gasket, and the overlapping part of the high polymer waterproof board is welded by using double-welded hot welding. The reinforced concrete secondary lining is poured by using an integral formwork trolley, the thickness of the reinforced concrete secondary lining is 60-80 cm, and the pouring is performed by layering and symmetrical vibration.

[0014] In an embodiment, the primary support layer is deformed, and when the monitoring data meets the preset deformation anomaly criterion, a radial grouting hole is drilled in the primary support layer at a deformation significant position, and the radial grouting hole is subjected to reinforced grouting, and the step further comprises: When the cumulative convergence value reaches 80% of the design reserved deformation amount and the deformation rate is still greater than 5 mm per day, a temporary vertical steel support is additionally arranged at the springing position of the deformation significant section while the reinforced grouting is performed.

[0015] The technical scheme of the present application effectively prevents groundwater from seeping in and structural failure by systematically constructing a primary waterproof layer in a soft rock large deformation section tunnel, reinforcing key nodes, dynamically responding to deformation, and forming a final composite waterproof system, and has the advantages of improving the waterproof reliability and structural durability of the soft rock waterproof layer of the soft rock large deformation section tunnel. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below, and obviously, other drawings can be obtained from the structures shown in the drawings without creative labor for those skilled in the art.

[0017] Figure 1 The flowchart of an embodiment of the soft rock waterproof layer construction method for a soft rock large deformation section tunnel provided by the present application is shown.

[0018] The objectives, functional characteristics and advantages of the present application will be further described with reference to the embodiments in combination with the accompanying drawings. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0021] In addition, if the embodiments of the present application involve descriptions of "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B simultaneously satisfy the scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears to be contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0022] The existing soft rock large deformation tunnel waterproof layer construction method has deficiencies in the waterproof performance of the primary support system, and the grouting reinforcement cannot form an effective waterproof bearing ring layer, resulting in the infiltration of groundwater along the construction gap. At the same time, the deformation monitoring and reinforcement treatment lack clear quantitative criteria and dynamic response mechanisms, and the best reinforcement opportunity is easily missed. In addition, the waterproof reinforcement measures of stress concentration parts such as arch feet are not systematic, and local weak links are easy to become water seepage channels, and there is a lack of organic connection between each waterproof process, and the overall waterproof reliability needs to be improved.

[0023] In order to solve the technical problem, the present application provides a soft rock waterproof layer construction method for a soft rock large deformation tunnel.

[0024] Please refer to Figure 1In an embodiment of the present application, the method for constructing a waterproof layer for a soft rock large deformation tunnel comprises: S10, spraying a concrete layer on a tunnel excavation profile, erecting a full-ring steel arch, applying system anchor rods, full-length grouting of the system anchor rods, and then spraying concrete to a designed thickness to form an initial support layer containing a grouting reinforcement ring; S20, applying a lock foot anchor pipe at the springing of the initial support layer and injecting grout into the lock foot anchor pipe to form a locally reinforced waterproof load-bearing body; S30, monitoring deformation of the initial support layer, and when the monitoring data meet a preset deformation anomaly criterion, drilling a radial grouting hole in the initial support layer at a deformation significant position and performing reinforcement grouting on the radial grouting hole; S40, after the initial support layer is deformed stably, laying a waterproof layer on the inner surface of the initial support layer and pouring a reinforced concrete secondary lining on the inner side of the waterproof layer, so that the initial support layer and the secondary lining jointly form a composite waterproof system.

[0025] For ease of understanding, some key terms in the present embodiment are explained as follows: Soft rock large deformation tunnel: refers to a tunnel excavation area with low surrounding rock strength, poor self-stability, and easy softening when encountering water, which often exhibits persistent and significant deformation of surrounding rock after excavation.

[0026] Initial load-bearing waterproof layer construction: refers to forming a support structure with initial load-bearing capacity and certain waterproof function on the surface of surrounding rock through spraying concrete, steel arch, anchor rod, and grouting at the initial stage of tunnel excavation.

[0027] Initial support layer: refers to a temporary or semi-permanent support structure immediately applied after tunnel excavation, mainly composed of sprayed concrete, steel arch, anchor rod, and grouting reinforcement ring, etc., for controlling surrounding rock deformation and maintaining tunnel stability.

[0028] Grouting reinforcement ring: refers to a high-strength and low-permeability area formed by injecting grout into the surrounding rock or support structure, thereby improving the overall stability and waterproof performance of the surrounding rock or support structure.

[0029] Key node waterproof performance enhancement: refers to taking local waterproof and load-bearing measures for specific positions in the tunnel structure where stress concentration or water leakage is prone to occur, such as the springing.

[0030] Lock foot anchor pipe: refers to a tubular member arranged at key positions such as the springing of the tunnel, used for injecting grout to reinforce the surrounding rock or support structure and form a local waterproof load-bearing body.

[0031] Localized Reinforced Waterproof Carrier: Refers to the area formed by methods such as lock foot anchor pipe grouting at specific parts of the tunnel structure, which has higher bearing capacity and better waterproof performance.

[0032] Dynamic Waterproof Reinforcement Based on Deformation Data: Refers to taking measures such as grouting to reinforce and waterproof the deformation significant parts in time when the deformation reaches a certain criterion according to the deformation monitoring data of the primary support layer.

[0033] Pre-set Deformation Abnormality Criterion: Refers to the quantitative standard set in advance during tunnel design or construction to judge whether the deformation of the primary support layer exceeds the normal range or has potential risks.

[0034] Radial Grouting Hole: Refers to the hole drilled along the radial direction of the tunnel, used to inject grout into the surrounding rock or primary support layer for reinforcement or waterproof reinforcement.

[0035] Reinforcement Grouting: Refers to local reinforcement and waterproof treatment of surrounding rock or support structure by injecting grout into radial grouting holes when deformation abnormalities occur in the primary support layer.

[0036] Final Composite Waterproof Layer Formation: Refers to laying a waterproof layer on the inner surface of the primary support layer after the deformation stabilizes, and pouring secondary lining to form a whole structure with long-term waterproof and bearing functions.

[0037] Waterproof Layer: Refers to a layer of flexible or semi-flexible material laid between the primary support layer and the secondary lining to block the infiltration of groundwater into the tunnel.

[0038] Reinforced Concrete Secondary Lining: Refers to the permanent reinforced concrete structure poured inside the waterproof layer, which serves as the main bearing and waterproof component of the tunnel, and forms a composite waterproof system with the primary support layer.

[0039] Composite Waterproof System: Refers to a waterproof structure composed of multiple layers of primary support layer, waterproof layer, and secondary lining, which has multiple barriers and synergistic effects.

[0040] The present application provides a soft rock waterproof layer construction method for soft rock large deformation section tunnel, which aims to improve the overall waterproof performance and structural stability of soft rock tunnel through a series of steps.

[0041] Specifically, the method includes initial waterproof layer construction. At the tunnel excavation profile, a layer of shotcrete can be applied first to preliminarily seal the rock surface. Subsequently, a steel arch can be erected, which can be installed in segments to form an open support structure. Then, systematic anchor rods, such as ordinary mortar anchor rods, can be applied and locally grouted to enhance the stability of the surrounding rock. On this basis, shotcrete can be applied again to the designed thickness to form an initial support layer. During the formation of the initial support layer, a certain range of grouting reinforcement rings can be formed inside the surrounding rock through grouting, thereby improving the overall strength and impermeability of the surrounding rock.

[0042] Further, the method includes key node waterproofing enhancement. At the arch foot of the initial support layer, a foot-locked anchor pipe can be applied. The foot-locked anchor pipe can be inserted and fixed after drilling with ordinary steel pipes. Subsequently, the foot-locked anchor pipe can be injected with grout, such as ordinary cement grout, through simple pumping to diffuse and solidify the grout, thereby forming a locally reinforced waterproof load-bearing body at the arch foot. This local reinforcement aims to improve the load-bearing capacity and impermeability of the arch foot area.

[0043] In addition, the method also includes dynamic waterproof reinforcement based on deformation data. Deformation monitoring of the initial support layer can be observed by manual inspection or simple displacement meters. When the monitoring data indicates that the deformation meets the preset abnormal criteria, for example, when obvious cracks or deformation to a certain extent are observed on the surface of the initial support layer, it is considered that the abnormal criteria are met. At this time, a radial grouting hole is drilled in the initial support layer at the deformation site, which can be constructed using conventional drilling equipment. Subsequently, the radial grouting hole is reinforced and grouted, such as using single-component cement grout, which is injected by a conventional grouting pump to reinforce and waterproof the surrounding rock or the initial support layer.

[0044] Finally, the method includes the formation of the final composite waterproof layer. After the deformation of the initial support layer stabilizes, such as when the deformation rate is observed to slow down significantly, a waterproof layer can be laid on the inner surface of the initial support layer. The waterproof layer can be made of conventional polyethylene film or asphalt roll, which is laid by lapping or bonding. Subsequently, a reinforced concrete secondary lining is poured on the inner side of the waterproof layer. The secondary lining can be poured in segments using conventional forms and concrete pumps. In this way, the initial support layer and the secondary lining together form a composite waterproof system, which aims to provide long-term structural stability and waterproof function.

[0045] The application builds a multi-level and dynamic response waterproof system through initial waterproof layer construction, key node waterproof enhancement, dynamic waterproof reinforcement based on deformation data, and final composite waterproof layer formation. This method effectively solves the problems of insufficient waterproof performance of initial support in soft rock large deformation section tunnel, lagging response of deformation monitoring, key node leakage, and poor connection of each waterproof process, thereby improving the overall waterproof reliability and long-term stability of soft rock tunnel.

[0046] In the embodiment of the application, the step of applying a shotcrete layer on the tunnel excavation profile, erecting a full-ring steel arch, applying system anchor rods and full-length grouting of the system anchor rods, and then applying shotcrete to the design thickness to form an initial support layer including a grouting reinforced ring, comprises: S11, immediately spraying a first layer of concrete on the tunnel excavation profile after excavation to preliminarily close the rock surface; S12, erecting the full-ring closed full-ring steel arch; S13, installing hollow grouting anchor rods as the system anchor rods at the arch and side wall parts; S14, injecting cement slurry through the hollow channel of the hollow grouting anchor rod, the grouting pressure being 0.3-0.8 MPa, and the grouting being continued until the hole returns the slurry; S15, laying a steel mesh on the outside of the full-ring steel arch and binding and fixing the steel mesh with the full-ring steel arch; S16, performing a second layer of shotcrete operation to completely wrap the full-ring steel arch, the steel mesh and the tray of the hollow grouting anchor rod, forming a dense initial support layer.

[0047] Specifically, immediately spraying a first layer of concrete on the tunnel excavation profile after excavation to preliminarily close the rock surface, which aims to quickly cover the freshly exposed rock surface, effectively prevent early relaxation, weathering and deformation of the surrounding rock, and provide a relatively stable working surface for the installation of subsequent support structures. The first layer of concrete usually uses wet or dry spraying process, and the thickness can be controlled within 5-10 cm, and its immediate application is crucial for the initial stability of soft rock surrounding rock.

[0048] Subsequently, the full-ring closed full-ring steel arch is erected. The full-ring steel arch serves as the main load-bearing component of the initial support, and its full-ring closed structure can ensure the continuous transmission of load in the entire circumferential direction of the tunnel, effectively resist radial and tangential pressure from the soft rock surrounding rock, and avoid local stress concentration. The steel arch can adopt the form of I-beam, H-beam or grid steel frame, and is achieved by welding, bolt connection or special connecting pieces.

[0049] Next, hollow grouting anchor rods, which serve as the system anchor rods, are installed at the arch and sidewall parts. The hollow grouting anchor rod is a self-drilling anchor rod, and its hollow channel inside allows grouting while drilling, thereby simplifying the construction process and ensuring the full combination of the anchor rod with the surrounding rock. The installation position and density of the hollow grouting anchor rod are determined according to the geological conditions of the surrounding rock and design requirements to achieve effective reinforcement of the surrounding rock.

[0050] Cement slurry is injected through the hollow channel of the hollow grouting anchor rod, and the grouting pressure is 0.3 MPa to 0.8 MPa, and the grouting is continued until the slurry returns at the orifice. This step aims to tightly combine the anchor rod with the surrounding rock through grouting, form a grouting reinforcement ring, and improve the overall strength and stability of the surrounding rock. The accurate control of the grouting pressure (0.3 MPa to 0.8 MPa) ensures that the slurry can fully penetrate the cracks of the surrounding rock, and the continuous grouting until the slurry returns at the orifice marks that the surrounding rock in the grouting range has reached a saturated state, thereby forming a dense reinforcement area.

[0051] On this basis, a steel mesh is laid on the outside of the full-ring steel arch and is fixed by being tied with the full-ring steel arch. The steel mesh provides tensile strength for the shotcrete layer, effectively preventing concrete spalling and cracking, and enhancing its integrity and ductility. The steel mesh is tied and fixed with the steel arch to ensure that the two bear forces together and form a composite load-bearing structure.

[0052] Finally, a second layer of shotcrete is performed to completely wrap the full-ring steel arch, the steel mesh, and the tray of the hollow grouting anchor rod, forming a dense primary support layer. The second layer of shotcrete completely covers all support components (steel arch, steel mesh, anchor rod tray), forming a primary support structure with strong integrity and high density. This not only protects the internal steel structure from corrosion, but also enables the components to collectively resist the pressure of the surrounding rock as a whole, ensuring the long-term stability and load-bearing capacity of the primary support layer.

[0053] Through the technical scheme, the application provides a fine and systematic primary support layer construction method, effectively solves the problems of insufficient surrounding rock cooperation and poor deformation control effect of the primary support of the soft rock large deformation section tunnel. The immediate spraying of the first layer of concrete can quickly close the rock surface, effectively inhibiting the early relaxation and deformation of the surrounding rock; the full-ring closed steel arch and the steel mesh together form a solid framework, providing strong structural bearing capacity; the hollow grouting anchor rod realizes deep reinforcement of the surrounding rock through an accurately controlled grouting process, forms a dense grouting reinforcement ring, significantly improves the overall strength and stability of the surrounding rock, and enhances the cooperation between the support structure and the surrounding rock. Finally, through the overall wrapping of the second layer of sprayed concrete, a dense and highly integrated primary support layer is formed, laying a solid foundation for the long-term stability of the tunnel and the effective laying of the subsequent waterproof layer, thereby ensuring the reliability of the entire composite waterproof system.

[0054] In the embodiment of the application, before the step of injecting cement slurry through the hollow channel of the hollow grouting anchor rod, the grouting pressure being 0.3 MPa to 0.8 MPa, and continuously grouting until the slurry returns at the orifice, the soft rock waterproof layer construction method for a soft rock large deformation section tunnel further comprises: S141, an initial pre-tightening force is applied to the hollow grouting anchor rod; wherein the initial pre-tightening force is not less than 60 kN.

[0055] Specifically, applying an initial pre-tightening force means that after the anchor rod is installed and preliminarily fixed, an external device (such as a hydraulic jack or a special tensioning device) is used to apply a pre-set tensile force to the anchor rod body. The tensile force is transmitted to the surrounding rock through the pressure plate at the head of the anchor rod, so that the anchor rod is in a stressed state before grouting and consolidation, thereby actively applying radial pressure to the surrounding rock, improving the stress state of the surrounding rock, and limiting the initial deformation of the surrounding rock. The application of this pre-tightening force aims to make the anchor rod work before the deformation of the surrounding rock occurs, improving the timeliness and effectiveness of the support. The initial pre-tightening force not less than 60 kN means that the pre-tension applied to the hollow grouting anchor rod should reach or exceed the value of 60 kN. This value is a lower limit value determined comprehensively according to factors such as the surrounding rock characteristics of the soft rock large deformation section tunnel, the tunnel size, the expected deformation, and the design bearing capacity of the anchor rod. Setting this minimum pre-tightening force is to ensure that the anchor rod can provide sufficient initial active support force, effectively inhibit the early deformation of the soft rock, and create favorable conditions for subsequent grouting reinforcement, preventing the anchor support effect from being not obvious due to insufficient pre-tightening force.

[0056] By the technical scheme, the initial pre-tightening force of no less than 60 kN is applied to the hollow grouting anchor rod before grouting, so that the anchor rod can actively apply pre-stress to the surrounding rock in the early stage of installation, effectively inhibiting the early deformation of soft rock. This active support can significantly improve the stress state of the surrounding rock and improve the self-bearing capacity of the surrounding rock, thereby reducing the deformation of the initial support layer. At the same time, the pre-tightening force ensures closer contact between the anchor rod body and the surrounding rock, providing better consolidation conditions for subsequent cement slurry injection, so that the grouting reinforcement effect is more ideal. Therefore, the scheme not only enhances the overall stability and bearing capacity of the initial support layer, but also provides a more stable foundation for the laying of the subsequent waterproof layer, thereby improving the reliability of the entire composite waterproof system.

[0057] In the embodiment of the present application, the step of forming a locally reinforced waterproof load-bearing body by applying a lock foot anchor pipe at the springing position of the initial support layer and injecting slurry into the lock foot anchor pipe comprises: S21, drilling an inclined borehole at the designed position of the springing position; S22, inserting a seamless steel pipe with slurry overflow holes into the inclined borehole; S23, connecting a grouting pipe through the seamless steel pipe and injecting cement slurry with a water-cement ratio of 0.35 to 0.4; S24, stopping grouting when the grouting pressure reaches 1.0 MPa to 2.0 MPa and the pressure is stable for no less than 5 minutes.

[0058] Specifically, an inclined borehole is drilled at the designed position of the springing position to provide an accurate channel for subsequent grouting operations. The setting of the inclined borehole can guide the slurry to penetrate the rock mass in the preset direction, effectively avoiding the existing initial support structure, and according to the stress characteristics and geological conditions of the springing position, the diffusion range and reinforcement effect of the slurry are optimized. The drilling equipment can be selected as a hydraulic or pneumatic drill, and the drilling angle and depth need to be accurately controlled according to the actual situation and design requirements on site to ensure that the slurry can effectively cover the target reinforcement area.

[0059] Subsequently, a seamless steel pipe with slurry overflow holes is inserted into the inclined borehole. The seamless steel pipe serves as a carrier for slurry, and the evenly distributed slurry overflow holes on the pipe wall are the key to achieving uniform diffusion of slurry in the borehole. These slurry overflow holes ensure that the slurry can overflow from multiple points of the steel pipe, rather than just the pipe end, thereby significantly improving the uniformity of slurry penetration in soft rock fissures and cavities, avoiding local accumulation or insufficient penetration of slurry. The material and strength of the seamless steel pipe ensure its structural integrity under high grouting pressure, and the size and spacing of the slurry overflow holes need to be optimized according to the viscosity of the slurry, the grouting pressure and the target reinforcement range.

[0060] On this basis, the cement slurry with a water-cement ratio of 0.35 to 0.4 is injected through the seamless steel pipe connected with the grouting pipeline. The accurate control of the water-cement ratio makes the prepared cement slurry have suitable fluidity and setting performance. A higher water-cement ratio may result in insufficient strength of the slurry, and a lower water-cement ratio may reduce the fluidity of the slurry, making it difficult to effectively penetrate the fine cracks. Therefore, the selection of the water-cement ratio of 0.35 to 0.4 can ensure the good permeability of the slurry while ensuring the strength and compactness of the slurry after solidification, thereby effectively filling the cracks and cavities in the rock mass and forming a solidified body. The preparation of the slurry should use high-speed stirring equipment to ensure that the slurry is uniform and free of lumps.

[0061] Finally, when the grouting pressure reaches 1.0 to 2.0 MPa and the pressure is stable for not less than 5 minutes, the grouting is stopped. The accurate control of the grouting pressure is the driving force to ensure the effective penetration and diffusion of the slurry. Raising the pressure to the range of 1.0 to 2.0 MPa can overcome the resistance inside the rock mass, making the slurry fully enter and fill the cracks. And the pressure being stable for not less than 5 minutes provides sufficient time for the slurry to penetrate and diffuse, and ensures that the slurry is fully solidified in the target area to form a dense reinforcement ring. During the grouting process, the grouting pressure is monitored in real time through the pressure gauge, and adjustments are made according to the actual situation to achieve the best grouting effect.

[0062] Through the above technical solutions, the grouting process at the arch foot of the primary support layer is significantly optimized. The use of inclined drilling and seamless steel pipes with overflow holes ensures that the slurry can be accurately and uniformly injected into the key stress area and potential water seepage channel at the arch foot. This injection method avoids local oversaturation or uneven penetration caused by concentrated injection of the slurry, greatly improving the diffusion efficiency and uniformity of the slurry in soft rock cracks and cavities. At the same time, by strictly controlling the cement slurry with a water-cement ratio of 0.35 to 0.4 and accurately setting the grouting pressure between 1.0 and 2.0 MPa and stable for not less than 5 minutes, it is ensured that the slurry can fully penetrate, diffuse and eventually form a high-strength, low-permeability solidified body. This fine grouting control not only effectively improves the compactness and bearing capacity of the rock mass at the arch foot, significantly enhances the waterproof performance of this area, but also avoids local weak links caused by insufficient or uneven grouting, thereby effectively solving the problems of water leakage and insufficient bearing capacity that may exist at the arch foot of the primary support layer, providing a solid foundation for the entire composite waterproof system, and significantly improving the long-term stability and waterproof reliability of the soft rock large deformation section tunnel.

[0063] In the embodiment of the present application, the preset deformation anomaly criterion is that the daily net clearance convergence value is greater than 30 mm, or the cumulative convergence value reaches 70% of the design reserved deformation amount and the deformation rate does not show a downward trend; the reinforcement grouting adopts cement-silicate double liquid slurry; The step of drilling a radial grouting hole in the primary support layer at a position where deformation is significant and performing reinforced grouting in the radial grouting hole comprises: S31, performing the reinforced grouting through the radial grouting hole with a depth of 3-5 meters, and the final pressure of the grouting is 0.5-1.5 MPa.

[0064] Specifically, the preset deformation anomaly criterion is an index for determining whether the deformation of the primary support layer reaches a critical state requiring intervention for reinforced grouting. The criterion includes two cases: one is that when the net clearance convergence value of the primary support layer monitored in a single day is greater than 30 mm, it indicates that the deformation rate is fast, and immediate reinforcement measures need to be taken; the other is that when the cumulative convergence value reaches 70% of the design reserved deformation and the deformation rate does not show a downward trend, it indicates that the primary support layer has approached its design deformation limit, and the deformation is still developing, which also requires reinforcement. These explicit quantitative indicators avoid subjective judgment and ensure the timeliness and necessity of reinforced grouting. The reinforced grouting uses cement-sodium silicate double-liquid slurry, which is a grouting material formed by mixing cement slurry and sodium silicate slurry in a certain proportion. During grouting, the two slurries are mixed in the hole or at the hole, and the rapid setting property of sodium silicate is used to accelerate the setting of cement slurry, thereby improving the early strength and water stopping effect. This double-liquid slurry has good permeability, controllable setting speed, and high early strength for soft rock strata, can quickly fill cracks and consolidate broken rock mass, effectively stop water and improve the bearing capacity of the stratum. The reinforced grouting is performed through the radial grouting hole with a depth of 3-5 meters, which aims to ensure that the grouting range can cover the soft surrounding rock behind the primary support layer to a certain depth, forming an effective reinforcement ring to control deep deformation. Too shallow grouting depth may not achieve the expected reinforcement effect, while too deep grouting may increase construction difficulty and cost. The final pressure of the grouting is 0.5-1.5 MPa, which is the final pressure at the end of the grouting operation, and its role is to control the diffusion range and density of the grouting slurry in the surrounding rock. Lower final pressure may result in non-dense grouting and poor reinforcement effect, while too high final pressure may cause surrounding rock splitting, causing unnecessary damage or slurry loss. This pressure range aims to ensure that the slurry can effectively fill and compact the surrounding rock to form a stable reinforced body.

[0065] By the technical scheme, the application can accurately determine when the primary support layer needs to be reinforced by grouting by setting clear deformation anomaly criteria, i.e., the single-day net empty convergence value is greater than 30 mm, or the cumulative convergence value reaches 70% of the designed reserved deformation and the deformation rate does not show a downward trend, thereby avoiding the uncertainty caused by subjective judgment and ensuring the timeliness and effectiveness of the reinforcement measures. The cement-sodium silicate double-liquid slurry is used for reinforcement grouting, and the characteristics of rapid setting and high early strength can quickly consolidate the soft surrounding rock and effectively control the continuous deformation and form a dense waterproof barrier. At the same time, by controlling the depth of the radial grouting hole to be 3-5 meters and the final grouting pressure to be 0.5-1.5 MPa, it is ensured that the slurry can fully penetrate and densify the surrounding rock to form a deep and uniform reinforced circle, thereby significantly improving the overall stability and waterproof performance of the primary support layer and effectively dealing with the challenges of soft rock large deformation.

[0066] In the embodiments of the application, the deformation of the primary support layer is monitored, and when the monitoring data meets the preset deformation anomaly criterion, the step of drilling radial grouting holes in the primary support layer at the deformation significant position and reinforcing the radial grouting holes by grouting further comprises: S32, interval drilling first sequence grouting holes and grouting the first sequence grouting holes; S33, after the slurry in the first sequence grouting holes is initially set, drilling second sequence grouting holes in the middle of adjacent first sequence grouting holes and grouting the second sequence grouting holes; wherein the entire grouting process adopts skip-hole construction.

[0067] Specifically, drilling the first sequence of grouting holes with intervals refers to first drilling and grouting a batch of holes in the area that needs to be reinforced by grouting. These holes are not arranged continuously and closely, but with a certain interval. For example, the first batch of grouting holes can be drilled along the tunnel axis or in the ring direction with an interval of 1-3 meters in the area where deformation is significant. This is done to avoid excessive concentration of grouting pressure in local areas, to provide space for the diffusion of grout, and to allow a portion of the area to be reinforced first. After the grout in the first sequence of grouting holes has initial set, that is, the initial setting process of the cement grout from liquid to plastic state is completed, it is ensured that the grout has lost its fluidity but has not completely hardened. The initial setting of the grout is a critical time node for subsequent construction. By waiting for the initial setting of the grout, it can be ensured that the reinforced ring formed by the first sequence of grouting has a certain strength and stability, which can effectively block the short-circuit flow of subsequent grouting grout and provide a relatively stable grouting environment for the second sequence of grouting. Subsequently, the second sequence of grouting holes is drilled between adjacent first sequence of grouting holes and grouting is performed. After the initial setting of the grout in the first sequence of grouting holes and the formation of the initial reinforced zone, the second sequence of grouting holes is drilled in the gap area between adjacent first sequence of grouting holes and grouting is performed. In this way, the reinforced ring formed by the first sequence of grouting can be used as a "partition wall" to guide the diffusion of the grout of the second sequence of grouting to the unreinforced area, thereby achieving a more uniform and more comprehensive reinforcement effect. The entire grouting process uses a skip-hole construction method, which is a grouting construction method that is performed in sequences, stages, and intervals, aiming to avoid the concentration of grouting pressure and the short-circuiting of grout, and to improve the grouting effect and construction safety. It emphasizes the non-continuous arrangement of grouting holes and the staged grouting, which can effectively control the grouting range and pressure, avoid stress concentration and stratum disturbance caused by one-time large-scale grouting, and ensure the uniformity and effectiveness of grouting reinforcement.

[0068] Through the above technical solution, the first sequence of grouting holes is drilled with intervals and grouting is performed, and after the grout in the first sequence of grouting holes has initial set, the second sequence of grouting holes is drilled between adjacent first sequence of grouting holes and grouting is performed, and the grouting process is combined with skip-hole construction. This effectively avoids the excessive concentration of grouting pressure in local areas and reduces the risk of secondary damage to the initial support layer. The initial reinforced ring formed by the first sequence of grouting can effectively guide the diffusion direction of the second sequence of grouting grout, ensuring that the grout can penetrate more uniformly into the deformation area, thereby significantly improving the uniformity and density of the reinforcement grouting, enhancing the overall bearing capacity and waterproof performance of the initial support layer, and providing more reliable protection for the long-term stable operation of the tunnel.

[0069] In the embodiment of the present application, before the step of applying a shotcrete layer on the tunnel excavation contour surface, erecting a full-ring steel arch, applying system anchor rods and performing full-length grouting on the system anchor rods, and then applying shotcrete to the designed thickness to form an initial support layer containing a grouting reinforced ring, the method for constructing a soft rock waterproof layer of a tunnel in a soft rock large deformation section further comprises: S101, before the working face excavation, a forepoling is constructed along the arch of the tunnel and grouting is performed on the forepoling, thereby forming a pre-reinforced arch shell outside the excavation contour.

[0070] Specifically, the forepoling is a common forepoling technique, which is usually composed of drill holes drilled forwardly along the axial direction of the tunnel and steel pipes inserted into the drill holes. The steel pipes can be seamless steel pipes or steel pipes with grouting holes, which function to form a pre-reinforced annular or arch structure in front of the working face to limit the loosening and deformation of the surrounding rock before excavation. The length, diameter, spacing and inclination angle of the forepoling are designed according to the surrounding rock conditions and the size of the tunnel. The grouting of the forepoling refers to injecting slurry into the surrounding rock through the steel pipes in the forepoling. The slurry can be cement slurry, cement-silicate slurry or other composite slurry. The purpose of grouting is to make the slurry penetrate, fill or compact the cracks, pores and loose areas in the surrounding rock, thereby improving the integrity, strength and stability of the surrounding rock. The grouting pressure and grouting amount need to be controlled according to the permeability of the surrounding rock, the properties of the slurry and the expected reinforcement effect. By constructing the forepoling and performing grouting, a pre-reinforced arch shell with a certain thickness and strength can be formed in the surrounding rock outside the tunnel excavation contour. This pre-reinforced arch shell can effectively redistribute the stress of the surrounding rock near the excavation face and provide additional bearing capacity, thereby restraining and supporting the surrounding rock before tunnel excavation, significantly reducing the initial deformation of the surrounding rock after excavation.

[0071] Through the above technical solution, before the working face excavation, a forepoling is constructed along the arch of the tunnel and grouting is performed on the forepoling, thereby forming a pre-reinforced arch shell outside the excavation contour. The application can effectively pre-reinforce and stabilize the surrounding rock before tunnel excavation. This pre-reinforced arch shell can bear part of the surrounding rock pressure in advance, limit the initial loosening and deformation of the surrounding rock after excavation, thereby significantly reducing the convergence amount and convergence rate of the surrounding rock after tunnel excavation. This not only provides a more stable working face for the subsequent construction of the primary support layer, reducing the construction risk, but also effectively controls the overall deformation of the tunnel in the soft rock large deformation section, laying a solid foundation for the long-term stable operation of the waterproof layer and the secondary lining, improving the reliability and durability of the entire composite waterproof system.

[0072] In the embodiment of the application, after the primary support layer is deformed and stabilized, the step of laying a waterproof layer on the inner surface of the primary support layer and pouring a reinforced concrete secondary lining on the inner side of the waterproof layer, so that the primary support layer and the secondary lining jointly constitute a composite waterproof system, comprises: S41, after the average net clearance convergence rate of the initial support layer is less than 2 mm per day for seven consecutive days, and there are no new obvious leakage points on the surface of the initial support layer, before laying the waterproof layer, the inner surface of the initial support layer is treated for flatness and the leakage points are sealed or drained.

[0073] Specifically, the condition that the average net clearance convergence rate of the initial support layer is less than 2 mm per day for seven consecutive days is intended to ensure that the initial support layer has achieved sufficient structural stability. Net clearance convergence rate refers to the rate of change of the tunnel's internal net clearance dimensions over time. An average of less than 2 mm per day for seven consecutive days indicates that the main deformation stage of the initial support layer has essentially ended, with minimal residual deformation and a stable structure. This indicator can be monitored by setting convergence measurement points and using equipment such as convergence meters or total stations to perform daily measurements and calculate the average value. Simultaneously, the condition that there are no new obvious seepage points on the surface of the initial support layer is intended to ensure that the initial support layer is in a hydrogeologically stable state. No new obvious seepage points mean that there are no new, visible, continuous water flows or drips on the surface of the initial support layer, indicating that groundwater activity in the surrounding rock has slowed down or has been effectively controlled through the drainage measures of the initial support layer. This indicator is mainly judged through on-site inspections and visual checks.

[0074] Based on this, before laying the waterproof layer, the inner surface of the initial support layer is treated for smoothness. Smoothness treatment refers to trimming the inner surface of the initial support layer to eliminate local protrusions and fill depressions, ensuring its surface meets the smoothness requirements for laying the waterproof layer. Specific treatment methods may include chiseling away high points, smoothing low points with mortar, or locally spraying a thin layer of concrete to provide a smooth, uniform base surface, preventing stress concentration or damage to the waterproof layer due to uneven base surface. In addition, seepage points need to be sealed or drained. Sealing refers to completely preventing water from entering the tunnel from the seepage point through grouting, caulking, or applying quick-setting sealing materials. Drainage refers to the organized diversion of seepage to the tunnel drainage system for seepage points with large volumes of water or those difficult to completely seal, using measures such as setting up drainage pipes, drainage channels, or drainage boards, preventing water from directly contacting the waterproof layer or accumulating behind it.

[0075] Through the aforementioned technical solution, the structural and hydrological stability of the initial support layer was rigorously quantitatively and qualitatively assessed before laying the waterproof layer and pouring the secondary lining, and the surface of the initial support layer underwent meticulous treatment. This not only ensured that the initial support layer possessed sufficient load-bearing capacity and deformation stability, preventing damage to the subsequent waterproof layer and secondary lining due to continuous ground deformation, but also eliminated surface defects through smoothing treatment, providing an ideal bonding interface for the waterproof layer and effectively preventing its damage. Simultaneously, the sealing or drainage of seepage points completely resolved the water hazard problem, preventing long-term erosion and damage to the waterproof layer by water pressure. Therefore, this solution significantly improves the overall reliability, durability, and waterproofing performance of the composite waterproofing system, effectively extending the tunnel's service life and reducing subsequent operation and maintenance costs.

[0076] In an embodiment of the present invention, the waterproof layer is a polymer waterproof board; After the initial support layer has stabilized due to deformation, a waterproof layer is laid on the inner surface of the initial support layer, and a reinforced concrete secondary lining is poured on the inner side of the waterproof layer, so that the initial support layer and the secondary lining together constitute a composite waterproof system. The steps also include: S42, the polymer waterproof membrane is fixed to the inner surface of the initial support layer using hot melt washers, and the overlapping parts of the polymer waterproof membrane are heat-sealed with double welds. S43, the reinforced concrete secondary lining is poured using an integral formwork trolley, and the thickness of the reinforced concrete secondary lining is 60 cm to 80 cm. During pouring, it is vibrated symmetrically in layers.

[0077] The polymer waterproof membrane is a flexible waterproof material made primarily of polymers. It possesses excellent tensile strength, puncture resistance, corrosion resistance, and aging resistance. Its flexibility allows it to better adapt to the minor deformations of the initial support layer, preventing cracking and maintaining waterproof integrity. During the installation of the waterproof layer, hot-melt washers are used to fix the polymer waterproof membrane to the inner surface of the initial support layer. These washers are typically made of a polymer compatible with the polymer waterproof membrane and are fused to the membrane using a hot air welding gun. A hole is located in the center of the washer, allowing fixing nails to pass through and secure the waterproof membrane to the initial support layer. This fixing method avoids damage or stress concentration to the waterproof membrane that may occur with traditional mechanical fixing, improving the waterproof performance and tear resistance of the fixing points. Furthermore, the overlapping parts of the polymer waterproof membrane are heat-sealed with double welds. Double-seam heat-sealing welding refers to forming two parallel and independent welds in the overlapping area of ​​two polymer waterproof membranes using specialized heat-sealing welding equipment. An inspection channel is usually left between the two welds, and the weld quality can be non-destructively tested using gas filling or vacuum testing methods to ensure the tightness and continuity of the welds, significantly improving the waterproof reliability of the overlapping area.

[0078] Furthermore, the reinforced concrete secondary lining is cast using an integral formwork trolley. An integral formwork trolley is a large, mobile steel formwork system capable of erecting long sections of lining formwork and pouring concrete in one go. Its advantages include ensuring smooth lining alignment and accurate dimensions, reducing construction joints, and improving the overall structural strength and crack resistance of the lining. The thickness of the reinforced concrete secondary lining is 60 to 80 centimeters. This thickness range is determined comprehensively based on surrounding rock conditions, tunnel span, design load, and waterproofing requirements. A thicker lining provides greater compressive and flexural stiffness, effectively resisting the deformation pressure of the surrounding rock and providing more stable protection for the waterproofing layer. Layered symmetrical vibration is performed during pouring. Layered vibration refers to the practice of not making each layer of concrete too thick during pouring, and then pouring the next layer only after the previous layer has been poured and compacted. Symmetrical vibration refers to the practice of arranging vibrators evenly on both sides or around the lining, and vibrating simultaneously or alternately to ensure that the concrete is uniformly compacted throughout the entire cross-section, eliminating air bubbles and improving the strength, durability and impermeability of the lining.

[0079] The above technical solution utilizes a polymer waterproof membrane as the waterproof layer. Its inherent flexibility and excellent impermeability allow it to better adapt to the deformation of the initial support layer in soft rock sections with large deformation, effectively maintaining the integrity of the waterproof layer. The hot-melt gasket fixing method avoids the puncture damage to the waterproof membrane caused by traditional mechanical fixing, ensuring the reliability of the waterproofing at the fixing points and ensuring a tight fit between the waterproof membrane and the initial support layer. Simultaneously, the overlapping parts of the polymer waterproof membrane are heat-sealed with double welds, providing double waterproofing protection. The weld quality can be effectively controlled through inspection channels, significantly improving the overall sealing and long-term impermeability of the waterproof layer. Furthermore, the reinforced concrete secondary lining is poured using an integral formwork trolley, ensuring the integrity, alignment, and dimensional accuracy of the lining, reducing construction joints, and improving structural strength. A lining thickness of 60 to 80 centimeters provides sufficient load-bearing capacity and an impermeable barrier, while layered symmetrical vibration ensures the concrete is dense and uniform, further enhancing the strength, durability, and impermeability of the lining. These measures work together to significantly enhance the overall waterproofing effect and structural stability of the composite waterproofing system, effectively addressing the complex geological conditions of the tunnel in the soft rock large deformation section and ensuring the long-term safe operation of the tunnel.

[0080] In an embodiment of the present invention, the step of monitoring the deformation of the initial support layer, and when the monitoring data meets the preset deformation anomaly criteria, drilling radial grouting holes in the initial support layer at the significantly deformed location and reinforcing the radial grouting holes with grouting further includes: S301, when the cumulative convergence value reaches 80% of the design reserved deformation and the deformation rate is still greater than 5 mm per day, while implementing the reinforcement grouting, temporary vertical steel supports are added to the arch foot part in the significantly deformed section.

[0081] The cumulative convergence value refers to the total deformation of the initial support structure into the tunnel over a period of time after excavation. The design allowance deformation is the maximum allowable deformation range preset for the tunnel structure based on engineering geological conditions and design experience. When the cumulative convergence value reaches 80% of the design allowance deformation, it indicates that the deformation of the tunnel surrounding rock has entered a highly active state and is close to the design limit. Simultaneously, if the deformation rate is still greater than 5 mm per day, it further indicates that the surrounding rock deformation is still developing rapidly and has not shown a convergence trend, suggesting a potential risk of structural instability. This criterion is designed to identify extreme deformation situations requiring stronger and more urgent support measures.

[0082] "While implementing the aforementioned reinforcing grouting" refers to simultaneously employing other support measures while radial grouting of the initial support layer is carried out to improve the mechanical properties and water-stopping effect of the surrounding rock. This simultaneous construction strategy aims to maximize the use of the construction window, and during the critical period of continuous deformation development, rapidly improve the overall bearing capacity and stability of the support structure through the synergistic effect of multiple measures, avoiding the delayed response or insufficient effect of a single measure.

[0083] Temporary vertical steel supports are flexible or semi-flexible support structures, typically made of H-beams, I-beams, or other steel profiles. These supports are formed by welding or bolting and are vertically installed at the tunnel arch foot. The arch foot is a critical stress point for the tunnel structure, bearing the loads from the superstructure and lateral compressive forces, and is also one of the areas most prone to deformation concentration. Adding temporary vertical steel supports directly provides additional vertical load-bearing capacity, effectively resisting rock subsidence and lateral compression, limiting deformation at the arch foot, and thus enhancing the overall stability and load-bearing capacity of the initial support structure. Their "temporary" nature indicates that their primary function is to provide short-term, rapid support during periods of severe rock deformation. They can be removed or retained as needed once the rock deformation has stabilized or after secondary lining construction is completed.

[0084] Through the above technical solution, when the deformation reaches 80% of the cumulative convergence value and the deformation rate is still greater than the extreme criterion of 5 mm / day, this application can effectively cope with the abnormally severe and rapid deformation of the surrounding rock in tunnel sections with large deformation in soft rock. Reinforcing grouting can improve the overall mechanical properties and water-stopping effect of the surrounding rock, while temporary vertical steel supports can provide immediate and significant structural bearing capacity for the arch foot, a key stress-bearing component, directly resisting the rapid compression and settlement of the surrounding rock. This dual, synchronous support measure avoids the response lag or insufficient effect of a single grouting measure under extreme deformation conditions, can quickly curb the continuous rapid deformation of the initial support structure, effectively control further instability of the surrounding rock, and thus significantly improve the overall stability and safety of the initial tunnel support, creating favorable conditions for subsequent construction.

[0085] The following example will provide a more detailed explanation of the above technical solution: A tunnel project's construction section is located in a typical soft rock area with large deformation. This area has low surrounding rock strength, poor self-stabilizing capacity, and abundant groundwater, easily leading to continuous large deformation and water leakage after tunnel excavation. Traditional tunnel waterproofing layer construction methods often face challenges under similar geological conditions, including insufficient initial support waterproofing performance, delayed deformation monitoring and reinforcement response, weak waterproofing at critical locations such as the arch foot, and loose connections between various waterproofing processes. To effectively address these issues, this method was adopted for soft rock waterproofing layer construction.

[0086] First, before excavation at the tunnel face, an advanced central pipe roof is constructed along the tunnel arch and grouting is performed on the advanced central pipe roof to form a pre-reinforced arch shell outside the excavation outline. This is intended to stabilize the surrounding rock in advance, provide a relatively stable environment for subsequent excavation, and initially suppress the initial deformation of the surrounding rock.

[0087] Subsequently, the initial load-bearing and waterproofing layer construction phase commenced. Immediately after tunnel excavation to the designed outline, the first layer of concrete, approximately 5 cm thick, was sprayed to initially seal the rock surface and prevent loosening and weathering of the surrounding rock. Following this, a fully enclosed steel arch frame, model H200, spaced 1 meter apart, was erected as the main load-bearing skeleton for the initial support. Hollow grouting anchors, 6 meters long and spaced 1.5 meters apart, were installed as system anchors at the arch and sidewall locations. Before grouting the hollow grouting anchors, an initial preload of no less than 60 kN was applied to actively control surrounding rock deformation. Cement grout with a water-cement ratio of 0.5 was injected through the hollow channels of the hollow grouting anchors, with the grouting pressure controlled between 0.3 MPa and 0.8 MPa, and grouting continued until grout returned to the borehole opening. This full-length grouting not only reinforces the surrounding rock, but more importantly, it forms a dense grouting reinforcement ring within the initial support layer. This significantly enhances the integrity and waterproofing performance of the support structure, effectively solving the problems of insufficient waterproofing performance and groundwater seepage along construction joints in traditional initial supports. Reinforcing mesh is laid on the outside of the steel arch frame and tied to it. Finally, a second layer of shotcrete is applied, completely encasing the steel arch frame, reinforcing mesh, and the trays of the hollow grouting anchors, forming a dense initial support layer with a designed thickness of 25 cm.

[0088] After the initial support layer is constructed, waterproofing is enhanced at key points. Locking anchor pipes are installed at the arch foot of the initial support layer, a stress concentration area. Specifically, at the designed location at the arch foot, an inclined borehole 8 meters deep is drilled at a 30-degree angle along the tunnel axis. A seamless steel pipe with overflow holes in its wall is inserted into the inclined borehole. A grouting pipeline is connected to the seamless steel pipe, and cement grout with a water-cement ratio of 0.35 to 0.4 is injected. Grouting is stopped when the grouting pressure reaches 1.0 MPa to 2.0 MPa and is maintained for at least 5 minutes. This creates a locally reinforced waterproof bearing structure at the arch foot, effectively solving the problem of insufficient and unsystematic waterproofing reinforcement measures at stress concentration areas such as the arch foot, which easily become channels for water leakage in existing technologies.

[0089] During tunnel construction, continuous deformation monitoring of the initial support layer is conducted. Monitoring data, including clearance convergence and crown settlement, is uploaded to a data platform in real time. When the monitoring data meets preset deformation anomaly criteria—for example, a single-day clearance convergence value greater than 30 mm, or a cumulative convergence value reaching 70% of the designed allowable deformation and the deformation rate not showing a decreasing trend—a dynamic waterproofing and reinforcement program based on deformation data is immediately initiated. Radial grouting holes with a depth of 3 to 5 meters are drilled in the initial support layer at locations with significant deformation, and cement-water glass dual-liquid grout is used for reinforcement grouting. The final grouting pressure is controlled between 0.5 MPa and 1.5 MPa. The entire grouting process employs a skip-hole construction method: first, first-sequence grouting holes are drilled at intervals and grouting is performed; after the grout in the first-sequence grouting holes has initially set, second-sequence grouting holes are drilled between adjacent first-sequence grouting holes and grouting is performed. This dynamic response mechanism, combined with clear quantitative criteria and a sequential skip-hole grouting method, solves the problem of untimely reinforcement caused by the lack of clear quantitative criteria and dynamic response mechanisms in deformation monitoring and reinforcement treatment in existing technologies. Furthermore, when the cumulative convergence value reaches 80% of the design-reserved deformation and the deformation rate is still greater than 5 mm per day, temporary vertical steel supports are added at the arch foot of the significantly deformed section while reinforcing grouting is being implemented to provide additional temporary support and prevent further deformation deterioration.

[0090] Finally, after the initial support layer has stabilized, the final composite waterproof layer is formed. The criteria for stable deformation are: the average net clearance convergence rate is less than 2 mm per day for seven consecutive days, and there are no new obvious leakage points on the surface of the initial support layer. Before laying the waterproof layer, the inner surface of the initial support layer is leveled, and all seepage points are sealed or drained to ensure the basic conditions for waterproof layer construction. A 2 mm thick polymer waterproof membrane is laid on the inner surface of the initial support layer. Hot-melt gaskets are used to fix the polymer waterproof membrane to the inner surface of the initial support layer, and the overlapping parts of the polymer waterproof membrane are heat-sealed with double welds to ensure the integrity and reliability of the waterproof layer. A reinforced concrete secondary lining is poured inside the waterproof layer. The secondary lining is poured using an integral formwork trolley, with a thickness of 60 cm to 80 cm. During pouring, symmetrical vibration is performed in layers to ensure the compactness and strength of the concrete. Through the above steps, the initial support layer and the secondary lining together constitute a composite waterproof system. Unlike existing technologies where the various waterproofing processes lack organic integration and operate independently, this method forms a truly composite waterproofing system through the synergistic effect of the grouting reinforcement ring inside the initial support, the local reinforcement of the waterproofing bearing body at the arch foot, dynamic reinforcement grouting, and the final waterproofing membrane and secondary lining. This significantly improves the overall waterproofing reliability and long-term stability of the tunnel.

[0091] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for constructing a waterproof layer for soft rock sections of tunnels with large deformation, characterized in that, The method for constructing a waterproof layer for soft rock sections of tunnels with large deformation includes: A shotcrete layer is applied to the tunnel excavation profile, a full-ring steel arch is erected, a system of anchor bolts is installed and the entire length of the system of anchor bolts is grouted, and then shotcrete is applied to the design thickness to form an initial support layer including a grouted reinforcement ring. Locking anchor pipes are installed at the arch foot of the initial support layer, and grout is injected into the locking anchor pipes to form a locally reinforced waterproof load-bearing body; Deformation monitoring is performed on the initial support layer. When the monitoring data meets the preset abnormal deformation criteria, radial grouting holes are drilled in the initial support layer at the location of significant deformation, and the radial grouting holes are reinforced with grout. After the initial support layer has stabilized due to deformation, a waterproof layer is laid on the inner surface of the initial support layer, and a reinforced concrete secondary lining is poured on the inner side of the waterproof layer, so that the initial support layer and the secondary lining together form a composite waterproof system.

2. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, The steps of applying a shotcrete layer to the tunnel excavation profile, erecting a full-ring steel arch frame, installing a system of anchor bolts and grouting the entire length of the anchor bolts, and then re-shotcreting with concrete to the designed thickness to form an initial support layer including a grouting reinforcement ring include: Immediately after excavation, the first layer of concrete is sprayed onto the tunnel excavation profile to initially seal the rock surface. Erect the fully enclosed ring-shaped steel arch frame; Hollow grouting anchors are installed at the arch and sidewall sections to serve as anchors for the system. Cement grout is injected through the hollow channel of the hollow grouting anchor rod at a pressure of 0.3 MPa to 0.8 MPa, and grouting continues until grout returns to the borehole. A steel mesh is laid on the outside of the full-ring steel arch frame and the steel mesh is tied and fixed to the full-ring steel arch frame; The second layer of shotcrete is then applied to completely enclose the trays of the full-ring steel arch, the steel mesh, and the hollow grouting anchor rods, forming a dense initial support layer.

3. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 2, characterized in that, Before the step of injecting cement grout through the hollow channel of the hollow grouting anchor at a grouting pressure of 0.3 MPa to 0.8 MPa and continuing grouting until grout returns to the borehole, the method for constructing a soft rock waterproof layer for tunnels with large deformation in soft rock sections further includes: An initial preload is applied to the hollow grouting anchor rod; wherein the initial preload is not less than 60 kN.

4. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, The steps of installing anchor pipes at the arch foot of the initial support layer and injecting grout into the anchor pipes to form a locally reinforced waterproof load-bearing body include: An inclined borehole is drilled at the designed location of the arch foot; A seamless steel pipe with overflow holes in its wall is inserted into the inclined borehole; The seamless steel pipe is connected to the grouting pipeline, and cement grout with a water-cement ratio of 0.35 to 0.4 is injected. Grouting should be stopped when the grouting pressure reaches 1.0 MPa to 2.0 MPa and is stabilized for at least 5 minutes.

5. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, The preset abnormal deformation criteria are: the daily net clearance convergence value is greater than 30 mm, or the cumulative convergence value reaches 70% of the designed reserved deformation amount and the deformation rate does not show a downward trend; the reinforcement grouting adopts cement-water glass dual-liquid grout. The deformation monitoring of the initial support layer, and the step of drilling radial grouting holes in the initial support layer at the significantly deformed location and reinforcing the radial grouting holes when the monitoring data meets the preset deformation anomaly criteria, includes: The reinforcing grouting is performed through radial grouting holes with a depth of 3 to 5 meters, and the final grouting pressure is 0.5 MPa to 1.5 MPa.

6. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 5, characterized in that, The deformation monitoring of the initial support layer, and the step of drilling radial grouting holes in the initial support layer at the significantly deformed location and reinforcing the radial grouting holes when the monitoring data meets the preset deformation anomaly criteria, further includes: The first grouting holes are drilled at intervals and grout is injected into the first grouting holes; After the grout in the first grouting hole has initially set, a second grouting hole is drilled between adjacent first grouting holes and grout is injected into the second grouting hole; wherein, the entire grouting process adopts skip-hole construction.

7. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, Before the steps of applying a shotcrete layer to the tunnel excavation profile, erecting a full-ring steel arch frame, installing system anchors and grouting the entire length of the system anchors, and then re-shotcreting concrete to the designed thickness to form an initial support layer including a grouting reinforcement ring, the method for constructing a soft rock waterproof layer for tunnels with large deformation in soft rock sections further includes: Before excavation at the tunnel face, an advanced central pipe roof is constructed along the tunnel arch and grouting is performed on the advanced central pipe roof to form a pre-reinforced arch shell outside the excavation outline.

8. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, After the initial support layer has stabilized due to deformation, a waterproof layer is laid on the inner surface of the initial support layer, and a reinforced concrete secondary lining is poured inside the waterproof layer, so that the initial support layer and the secondary lining together constitute a composite waterproof system. The steps include: After the average net clearance convergence rate of the initial support layer is less than 2 mm per day for seven consecutive days, and there are no new obvious water leakage points on the surface of the initial support layer, the inner surface of the initial support layer is treated for flatness and water leakage points are sealed or drained before the waterproof layer is laid.

9. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in claim 1, characterized in that, The waterproof layer is a polymer waterproof board; After the initial support layer has stabilized due to deformation, a waterproof layer is laid on the inner surface of the initial support layer, and a reinforced concrete secondary lining is poured on the inner side of the waterproof layer, so that the initial support layer and the secondary lining together constitute a composite waterproof system. The steps also include: The polymer waterproof membrane is fixed to the inner surface of the initial support layer using hot melt washers, and the overlapping parts of the polymer waterproof membrane are heat-sealed with double welds. The reinforced concrete secondary lining is poured using an integral formwork trolley. The thickness of the reinforced concrete secondary lining is 60 cm to 80 cm, and it is vibrated symmetrically in layers during pouring.

10. The method for constructing a waterproof layer for soft rock tunnels with large deformation sections as described in any one of claims 1 to 9, characterized in that, The deformation monitoring of the initial support layer, and the step of drilling radial grouting holes in the initial support layer at the significantly deformed location and reinforcing the radial grouting holes when the monitoring data meets the preset deformation anomaly criteria, further includes: When the cumulative convergence value reaches 80% of the designed reserved deformation and the deformation rate is still greater than 5 mm per day, while implementing the reinforcement grouting, temporary vertical steel supports are added to the arch foot of the significantly deformed section.

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