Hidden water stop and drainage system for TBM non-pressure water delivery tunnel and construction method thereof

Abstract

The invention provides a concealed water stop and drainage system of a TBM non-pressure water delivery tunnel and a construction method of the concealed water stop and drainage system, and relates to the technical field of hydraulic tunnel construction. The system comprises a prefabricated inverted arch, a cast-in-place side top arch, a water stop structure and a drainage structure. The water stop structure is composed of a side top arch water stop belt in the cast-in-place side top arch and a bottom plate water stop belt on the surface of the prefabricated inverted arch, the side top arch water stop belt and the bottom plate water stop belt are connected through vulcanization to form a continuous closed annular water stop system, joint water seepage is effectively prevented, and the overall waterproof performance is improved. The drainage structure comprises a reducing four-way pipe, an annular drainage pipe and a water outlet drainage pipe which are arranged at intervals in the axial direction of the tunnel, and the reducing four-way pipe, the annular drainage pipe and the water outlet drainage pipe are all pre-buried in cast-in-place edge top arch concrete and fixed through non-load-bearing steel bars, so that a drainage system is hidden. According to the arrangement, seepage leakage and seepage along the lining are avoided, the space regularity and attractiveness are improved, and the reliability and maintainability of the system are enhanced.

Description

Technical Field

[0001] This invention relates to the field of hydraulic tunnel construction technology, and in particular to a concealed drainage system for TBM-based unpressurized water conveyance tunnels and its construction method. Background Technology

[0002] In tunnel engineering using open-face TBMs (tunnel boring machines), the inability to pre-embed waterstops in the precast invert sections makes it difficult for the waterstops installed at the cast-in-place side arch sections to achieve continuous closure at the circumferential construction joints or structural joints, often resulting in interruptions at the precast invert joint connection point. This structural defect causes seepage channels to easily form at the bottom of the circumferential joints in the overall lining structure, leading to groundwater infiltration from the outside in, causing severe water accumulation in the tunnel chamber, and affecting operational safety and durability.

[0003] To address the aforementioned issues, existing technologies attempt to place the waterstop on the upper surface of the precast invert arch and achieve a circumferential closure, which is then compacted and sealed during the subsequent pouring of the joint concrete. However, this arrangement presents two key technical challenges: First, to ensure the integrity of the lining structure, the circumferential reinforcement between the precast invert arch and the cast-in-place side arch needs to be welded together to form a continuous load-bearing system. When the waterstop crosses this area, to avoid damaging the integrity of the waterproof layer, the design principle of the reinforcement avoiding the waterstop is often adopted, resulting in the circumferential reinforcement needing to be arranged around it. This weakens the continuity of the reinforcement skeleton, creating a localized stress concentration zone at the circumferential joint, becoming a weak point in the structure. Second, the bonding quality between the waterstop and the upper surface of the precast invert arch is difficult to guarantee. If the interface is not tightly bonded, voids or debonding may occur, thereby reducing the reliability and durability of the waterstop system and making it difficult to construct a stable and effective waterproof barrier.

[0004] Furthermore, the design level of the drainage system of unpressurized water conveyance tunnels, which are key water conveyance facilities in water conservancy projects, directly affects the actual groundwater pressure borne by the lining structure, further impacting the structure's safety, stability, and service life. Currently, commonly used drainage system layouts mainly include two types: one is to pre-embed longitudinal drainage pipes inside the reinforced concrete lining, introduce seepage water from the surrounding rock through boreholes, and insert drainage perforated pipes, with the gaps around the pipes sealed with cement mortar; the other is to install circumferential drainage pipes exposed in the tunnel wall, connecting them to the drainage perforated pipes via tee fittings. Although the above schemes have the advantages of convenient construction and short construction period, they still have significant drawbacks in practical application: on the one hand, external seepage water often drips into the tunnel chamber along the pipes or seeps along the lining surface, not only affecting the cleanliness of the tunnel environment but also posing a safety hazard to maintenance personnel; on the other hand, exposed pipes in the tunnel interior significantly reduce the spatial regularity and visual aesthetics of the tunnel interior, which is detrimental to the overall improvement of the quality of modern water conservancy engineering construction.

[0005] In summary, there is an urgent need to propose a novel concealed drainage and waterproofing system suitable for unpressurized water conveyance tunnels constructed using the TBM method. This system effectively connects the side arch waterstop with the bottom slab waterstop to form a closed annular waterproofing system, achieving full circumferential closure of the waterstop structure at circumferential construction joints and structural joints. This fundamentally solves the problem of external water seepage in the bottom slab area of ​​the "precast invert arch + cast-in-place side arch" composite lining structure. Simultaneously, the circumferential drainage pipes and reducing four-way pipes are pre-embedded inside the side arch lining structure, satisfying both the functional requirement of orderly groundwater discharge and the concealed arrangement of drainage components, thus balancing engineering functionality and aesthetic requirements. Furthermore, by adopting a nested socket connection method between pipe fittings and a threaded interface design at the lower branch of the reducing four-way pipe, the anti-clogging capability of the drainage system can be effectively improved, providing convenient conditions for later inspection and maintenance, and significantly enhancing the reliability and maintainability of the system during long-term operation. Summary of the Invention

[0006] The purpose of this invention is to provide a concealed drainage system for TBM unpressurized water conveyance tunnels and its construction method, so as to alleviate the technical problem of circumferential construction joint seepage caused by the difficulty in continuously closing the waterstop at the joint between the precast invert arch and the cast-in-place side arch.

[0007] In a first aspect, the TBM unpressurized water conveyance tunnel concealed drainage system provided by the present invention includes: a precast invert arch, a cast-in-place side arch, a water-stopping structure, and a drainage structure. The water-stopping structure consists of a side-top arch water-stopping strip installed in the cast-in-place side-top arch and a bottom plate water-stopping strip installed on the surface of the precast invert arch. The side-top arch water-stopping strip and the bottom plate water-stopping strip are connected by vulcanization to form a continuous closed annular water-stopping system. The drainage structure includes multiple reducing four-way pipes, circumferential drainage pipes, and drainage pipes at the outlet holes, which are arranged at intervals along the tunnel axis. The reducing four-way pipes, the circumferential drainage pipes, and the drainage pipes at the outlet holes are all pre-embedded in the lining concrete of the cast-in-place side arch and fixed by non-stressed steel bars.

[0008] In conjunction with the first aspect, the present invention provides a first possible implementation of the first aspect, wherein the side arch waterstop is an embedded rubber waterstop with a thickness of 8-12 mm and a width of 350-450 mm, the bottom end of the side arch waterstop extends into the precast invert arch and is used for on-site vulcanization connection with the bottom plate waterstop.

[0009] In conjunction with the first aspect, the present invention provides a second possible implementation of the first aspect, wherein the edge arch waterstop is provided with a reserved steel bar hole for the circumferential reinforcing steel bar to pass through, and the gap between the reserved steel bar hole and the circumferential reinforcing steel bar is sealed by a steel ring edge and a leak-proof sealant.

[0010] In conjunction with the first aspect, the present invention provides a third possible implementation of the first aspect, wherein each of the circumferential drain pipes is provided with a plurality of the reducing four-way pipes spaced apart in the circumferential direction; The reducing four-way pipe has an upper branch pipe and a lower branch pipe. The upper branch pipe is connected to a radial drainage flower pipe, and the lower branch pipe is detachably connected to an external threaded cap.

[0011] In conjunction with the first aspect, the present invention provides a fourth possible implementation of the first aspect, wherein the bottom plate waterstop is pressed together by a stainless steel pressure plate connected to the precast invert arch.

[0012] In conjunction with the fourth possible implementation of the first aspect, the present invention provides a fifth possible implementation of the first aspect, wherein the precast invert arch, the bottom plate waterstop, and the stainless steel pressure plate are filled with jointed concrete; The surface of the jointed concrete is provided with a two-way cross slope.

[0013] Secondly, the construction method for the concealed drainage system in a TBM-based unpressurized water conveyance tunnel provided by this invention includes the following steps: A bottom plate waterstop is installed on the surface of the precast invert arch, and a side arch waterstop is installed inside the cast-in-place side arch. The edge arch waterstop and the bottom plate waterstop are connected by vulcanization to form a continuous closed ring waterstop system; Multiple reducing four-way pipes, circumferential drainage pipes, and drainage pipes at the water outlets are pre-embedded in the lining concrete of the cast-in-place side arch and fixed with non-stressed steel bars.

[0014] In conjunction with the second aspect, the present invention provides a first possible implementation of the second aspect, wherein the construction method of the concealed drainage system for the TBM unpressurized water conveyance tunnel further includes: Pre-reserved steel bar holes are provided on the edge arch waterstop for the circumferential reinforcing bars to pass through, and the edges are wrapped with steel rings and sealed with anti-leakage adhesive. Multiple reducing four-way pipes are arranged at circumferential intervals in each circumferential drainage pipe. Each reducing four-way pipe has an upper branch pipe and a lower branch pipe. The upper branch pipe is connected to the radial drainage flower pipe, and the lower branch pipe is detachably connected with an external threaded cap. The bottom plate waterstop is pressed onto the precast invert arch by a stainless steel pressure plate, and joint concrete is poured on the precast invert arch, the bottom plate waterstop and the stainless steel pressure plate. The surface of the joint concrete is provided with a two-way transverse slope.

[0015] In conjunction with the second aspect, the present invention provides a second possible implementation of the second aspect, wherein, before the installation of the base plate waterstop, the base surface of the precast invert arch is treated, and the treatment step includes: The bolt grooves and joint areas on the surface of the precast invert are cleaned and dried until they are saturated and dry. Then, acrylic emulsion mortar is used to backfill and smooth the surface. Apply two coats of interface agent to the surface of the precast invert arch, with an interval of ≥3 hours. After the surface is dry, apply SK hand-applied polyurea to form an adhesive layer.

[0016] In conjunction with the second possible implementation of the second aspect, the present invention provides a third possible implementation of the second aspect, wherein the base plate waterstop is laid on the adhesive layer; The edge arch waterstop and the bottom plate waterstop are connected by vulcanization to form a vulcanized waterstop connection part; The base plate waterstop and the vulcanized connection of the waterstop are hammered to make the base plate waterstop and the vulcanized connection of the waterstop adhere to the adhesive layer.

[0017] The embodiments of this invention bring the following beneficial effects: By vulcanizing the waterstop strip of the cast-in-place side arch to the bottom plate waterstop strip of the precast invert arch surface, a continuous closed ring-shaped waterstop system is formed, effectively solving the seepage problem at the joint between the precast invert arch and the cast-in-place side arch, and significantly improving the overall waterproof performance of the lining structure. Simultaneously, the reducing four-way pipe, circumferential drainage pipe, and drainage pipe at the outlet holes in the drainage structure are all pre-embedded in the lining concrete of the cast-in-place side arch and fixed by non-stressed steel bars, achieving a concealed layout of the drainage system. This not only avoids the problem of external seepage dripping into the cavern along the pipes or seeping along the lining surface, but also improves the spatial regularity and visual aesthetics of the cavern interior, and enhances the long-term reliability and maintainability of the system.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of the present invention, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional schematic diagram of the concealed drainage system for a TBM-based unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 2 This is a plan view of the prefabricated invert arch of the concealed drainage system for TBM unpressurized water conveyance tunnels provided in an embodiment of the present invention. Figure 3This is a cross-sectional view of the prefabricated invert arch of the concealed drainage system for TBM unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 4 Water-stop sample at the prefabricated invert arch of the concealed drainage system for TBM unpressurized water conveyance tunnel provided in this embodiment of the invention. Figure 1 ; Figure 5 Water-stop sample at the prefabricated invert arch of the concealed drainage system for TBM unpressurized water conveyance tunnel provided in this embodiment of the invention. Figure 2 ; Figure 6 A three-dimensional schematic diagram of the water-stopping arrangement at the prefabricated invert arch of the TBM unpressurized water conveyance tunnel concealed water-stopping and drainage system provided in an embodiment of the present invention. Figure 7 This is a cross-sectional view of the tunnel top drainage arrangement of the concealed drainage system for a TBM unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 8 This is a schematic diagram of the water outlet of the concealed drainage system for a TBM unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 9 This is a schematic diagram of the drainage hole of the concealed drainage system for a TBM unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of the reducing four-way pipe of the concealed drainage system for a TBM unpressurized water conveyance tunnel provided in an embodiment of the present invention. Figure 11 This is a schematic diagram of a concealed drainage system for a TBM-based unpressurized water conveyance tunnel provided in an embodiment of the present invention.

[0021] Icons: 1-Side arch waterstop; 2-Circumferential reinforcing steel; 3-Bottom slab waterstop; 4-Waterstop strip; 5-Stainless steel pressure plate; 6-Reserved reinforcing steel hole; 7-Cast-in-place side arch; 8-Precast invert arch; 9-Waterstop vulcanized connection; 10-Bolt groove; 11-Road spike hole; 12-Jointed concrete; 13-Interface agent and hand-scraped polyurea surface layer; 14-Circumferential drainage pipe; 15-Reducing four-way pipe; 16-Radial drainage flower pipe; 17-Tunnel initial support; 18-Drainage pipe at water outlet; 19-Drainage borehole; 20-Sealing sleeve; 21-External thread cap; 22-Distribution reinforcing steel. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only to describe differences in name and should not be construed as indicating or implying relative importance. Physical quantities in formulas, unless otherwise specified, should be understood as basic quantities in the International System of Units (SI), or derived quantities derived from basic quantities through mathematical operations such as multiplication, division, differentiation, or integration.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] like Figures 1 to 11 As shown, this embodiment provides a concealed drainage system and its construction method suitable for TBM-based construction of unpressurized water conveyance tunnels using a "precast invert arch + cast-in-place side-top arch" lining structure. This system aims to solve the problem of interrupted waterproofing at the bottom of the circumferential construction joint caused by the inability to pre-embed a waterstop in the precast invert arch in traditional construction methods. It also overcomes the shortcomings of existing drainage systems, such as exposed leakage, space encroachment, and maintenance difficulties, achieving an integrated design of full-circumference closed waterproofing and concealed drainage.

[0026] The concealed drainage and waterproofing system for the TBM unpressurized water conveyance tunnel provided in this embodiment includes: a precast invert arch 8, a cast-in-place side arch 7, a water-stopping structure, and a drainage structure. The water-stopping structure consists of a side arch water-stopping strip 1 installed inside the cast-in-place side arch 7 and a bottom plate water-stopping strip 3 laid on the upper surface of the precast invert arch 8. The cast-in-place side arch 7 is located inside the tunnel's initial support 17. The side arch water-stopping strip 1 extends downwards from the top along both sides, with a reserved length at its bottom extending into the precast invert arch area; the bottom plate water-stopping strip 3 is laid circumferentially at the joint between two adjacent precast invert arches. The two are connected by on-site vulcanization to form a continuous closed annular water-stopping system, thereby achieving full-section waterproof sealing at the circumferential construction joint or structural joint, effectively blocking the channel for groundwater to seep into the tunnel from the bottom of the annular joint.

[0027] The drainage structure includes multiple reducing four-way pipes 15 spaced along the tunnel axis, circumferential drainage pipes 14, and drainage pipes 18 at the outlet holes. All of the above drainage components are pre-embedded in the lining concrete of the cast-in-place side arch 7 and fixed with non-stressed steel bars to ensure no displacement during the pouring process. This design achieves a completely concealed layout of the drainage system, avoiding the leakage risks and visual interference of exposed pipes, and improving the overall aesthetics and operational safety of the project.

[0028] The edge arch waterstop 1 adopts a centrally embedded rubber waterstop, preferably made of EPDM or natural rubber composite material with excellent aging resistance and tear resistance. In this embodiment, the waterstop is 10mm thick and 400mm wide, meeting the strength and deformation adaptability requirements for long-term service under high-pressure water environment.

[0029] The waterstop is longitudinally positioned at the midpoint of the cast-in-place side arch 7, forming a U-shape around the perimeter in cross-section. Both ends extend downwards to near the top surface of the precast invert arch, with approximately 10cm reserved for on-site vulcanization connection with the base slab waterstop 3. This design ensures a seamless connection between the upper and lower sections of the waterstop at the joint, forming a complete and sealed waterproof ring. Furthermore, a waterstop strip 4 is installed within the joint between the cast-in-place side arch 7 and the precast invert arch 8.

[0030] Furthermore, to avoid affecting the overall load-bearing performance of the lining structure, the present invention provides multiple pre-reserved steel bar holes 6 on the edge arch waterstop 1, allowing the circumferential load-bearing steel bars 2 to pass directly through. The pre-reserved steel bar holes 6 are located inside the distribution steel bars 22, which are spaced apart along the circumference of the tunnel and are all parallel to the tunnel axis. This design allows the circumferential steel bars to pass continuously, avoiding the stress concentration problem caused by the steel bars going around in the traditional method, and significantly enhancing the structural continuity and load-bearing capacity of the circumferential joint area.

[0031] To address the potential leakage path caused by the gap between the reserved rebar hole 6 and the circumferential reinforcing bar 2, this invention employs a dual protective measure of "steel ring edging + leak-proof adhesive sealing": a metal steel ring is fitted around the rebar hole, and the gap around the hole is completely filled and sealed with high-performance polyurethane or epoxy-based leak-proof adhesive. This treatment method ensures both physical isolation between the rebar and the waterstop and reliable waterproofing at the interface, preventing moisture from penetrating along the rebar.

[0032] The bottom slab waterstop 3 is a flat rubber waterstop with a width of 400mm, laid above the joint area between the two precast invert arches 8. Its main function is to continue the waterproofing from the side arch waterstop 1 and achieve a full-ring closure through vulcanization.

[0033] Before installation, the base surface of the precast invert arch 8 must be strictly treated: 1. Clean the bolt grooves 10 and the area of ​​the invert joint on the surface of the precast invert 8, removing debris, dust, and oil stains; 2. After rinsing with high-pressure water, dry evenly until the substrate reaches a "saturated surface dry" state; 3. Use acrylic emulsion mortar to backfill and smooth the sunken areas, ensuring a smooth and flat surface free of bubbles, cracks, and sagging. 4. Apply two coats of the special interface agent to the treated substrate (each coat is approximately 600mm wide), with an interval of at least 3 hours between coats to ensure full curing; 5. After the interface agent has dried to the touch, apply a layer of SK hand-applied polyurea waterproof adhesive layer with a thickness of about 3mm (width about 500mm). The working environment should be kept clean to prevent dust and water droplets from affecting the bonding effect.

[0034] After completing the above-mentioned base surface treatment, the bottom plate waterstop 3 is accurately laid on the polyurea adhesive layer. Subsequently, the reserved end of the edge arch waterstop 1 is vulcanized and connected to the bottom plate waterstop 3 on site to form the vulcanized joint 9 of the waterstop. The vulcanization process uses portable hot melt welding equipment, controlling the temperature between 140 and 160°C, with moderate pressure, and a time of not less than 15 minutes to ensure that the joint strength is not less than 80% of the base material.

[0035] After the connection is completed, use a rubber hammer or a special compaction tool to repeatedly pound and compact the bottom plate waterstop 3 and the vulcanized connection part 9 of the waterstop, so that it can fully adhere to the polyurea layer below, remove air between the interfaces, and improve the bonding density.

[0036] To further enhance the anchoring stability of the waterstop, a stainless steel pressure plate 5 is used for mechanical clamping. The stainless steel pressure plate 5 is prefabricated into an arc shape according to the curvature of the precast invert arch, and holes are drilled on-site to match the bolt positions to avoid jamming during installation. During installation, the stainless steel nuts on both sides are tightened simultaneously. The stainless steel nuts fit into the spike holes 11 on the precast invert arch 8 to ensure uniform pressure distribution and prevent local voids.

[0037] Finally, joint concrete 12 is poured within the area jointly covered by the precast invert arch 8, the bottom slab waterstop 3, and the stainless steel pressure plate 5. This concrete not only further compacts the waterstop but also participates in structural force transmission, improving the overall integrity of the joint. To facilitate drainage, the surface of the joint concrete 12 is provided with a two-way cross slope, preferably 1% to 2%, so that any water accumulation that may occur during construction or maintenance can drain to both sides of the centerline, avoiding stagnation that could affect civilized construction.

[0038] The drainage structure includes a set of drainage components arranged at regular intervals along the tunnel axis. Each set includes a circumferential drainage pipe 14, multiple reducing four-way pipes 15, and a drainage pipe 18 at the outlet.

[0039] Among them, the circumferential drainage pipe 14 is laid along the circumference of the tunnel inside the side arch. It is made of high-density polyethylene (HDPE) PE pipe with a diameter of φ75mm, which has good flexibility and corrosion resistance. The pipe is firmly tied to the non-load-bearing steel bars to prevent displacement during concrete vibration.

[0040] On the circumferential drainage pipe 14, a reducing four-way pipe 15 is installed at approximately 40° intervals along the circumference, for a total of 4 pipes per ring, evenly distributed in the arch crown and the two sides of the arch waist area. The four-way pipe is made of PVC material and is pre-embedded in the cast-in-place side arch 7 concrete.

[0041] The reducing four-way pipe 15 has two functional branches: Upper branch pipe: φ100mm outer diameter, 5mm wall thickness, used to connect to the drainage borehole 19 on the surrounding rock side, with a radial drainage perforated pipe 16 inserted inside. During construction, a φ90mm drainage hole is drilled outward through this branch pipe to the designed depth, and a φ75mm radial PVC drainage perforated pipe wrapped with 300g / m² geotextile is inserted. The annular gap between the two is sealed by a nested φ90mm PVC sealing sleeve 20, achieving good water stoppage and structural support.

[0042] Lower branch pipe: outer diameter φ110mm, wall thickness 5mm, pipe diameter larger than upper branch pipe to facilitate smooth passage of the sealing sleeve. The lower branch pipe has a 5cm long internal thread section at the end, fitted with a φ100mm PVC external thread cap 21 for temporary sealing.

[0043] The key advantage of this design is that when poor drainage or leakage is found during operation, the external threaded cap 21 can be easily removed to open the maintenance channel from below and dredge and clean the internal drainage pipe. This effectively addresses the blockage caused by siltation or calcium deposits, greatly improving the maintainability and long-term operational reliability of the system.

[0044] In addition, the drainage pipes 18 at the bottom of the water outlets on both sides of the lining structure are also embedded in the concrete. The pipe material has been changed from conventional PE to a more rigid PVC material (φ75mm) to resist the deformation under the weight during the concrete pouring process and ensure that the water outlet channel is unobstructed and stable.

[0045] In an optional implementation, in order to meet the deformation adaptation requirements under complex working conditions such as high water head, dynamic load and uneven settlement, the present invention provides a gradient modulus composite waterstop as a preferred structure for the side arch waterstop 1 and / or the bottom plate waterstop 3.

[0046] The composite waterstop is composed of three layers: the middle layer is made of high-elasticity ethylene propylene diene monomer (EPDM) rubber, 6mm thick, with a Shore A hardness of 60A, used to absorb joint opening and shear displacement; the two outer layers are made of tear-resistant reinforced neoprene rubber (CR) + fiber fabric interlayer, each 2mm thick, with a Shore A hardness of 75A, significantly improving puncture resistance and fatigue fracture resistance; the layers are integrally formed by hot-pressing vulcanization, with an interfacial shear strength ≥1.2MPa. Compared with single-material waterstops, this composite structure has a service life increased by more than 40% in cyclic tensile and compressive tests, and still maintains complete waterproof function when the joint opening reaches 30mm.

[0047] In an optional implementation, the adaptive sealing sleeve includes: an external rigid sleeve: pre-embedded around the pre-drilled holes in the waterstop, made of Q235B galvanized steel pipe, with an inner diameter slightly larger than the diameter of the circumferential reinforcing bar 2 (e.g., a φ28mm reinforcing bar with a φ32mm sleeve); an internal elastic seal: a built-in double-lip rubber sealing ring, clamped to the surface of the reinforcing bar, with the lips facing the opposite direction of water flow to form a bidirectional water-stop barrier; and an intermediate filling layer: injected with low-shrinkage epoxy resin, which, after curing, forms an integral bond with the reinforcing bar, sleeve, and waterstop. This component can be prefabricated and installed on the edge arch waterstop 1 in the factory, and on-site positioning and sealing can be completed simply by inserting the reinforcing bar, greatly reducing the risk of construction errors.

[0048] In addition, based on the original reducing four-way pipe 15, its functions have been expanded to include drainage, grouting repair and health monitoring, thus creating a comprehensive operation and maintenance channel with "one pipe for multiple uses".

[0049] (1) Grouting Repair Mode: When local voids or leaks are detected behind the lining, the external threaded cap 21 can be removed, a high-pressure grouting pump can be connected, and the modified epoxy grout or ultrafine cement grout can be injected into the surrounding rock fissures or concrete voids through the lower branch pipe → reducing four-way body → upper branch pipe to achieve trenchless rapid repair. Supported pressure range: 0.5 to 3.0 MPa; maximum grouting depth can reach 15m.

[0050] (2) Health monitoring interface: A φ10mm central through hole is reserved inside the reducing four-way pipe 15, through which the upper and lower branch pipes pass, for later insertion of distributed fiber optic sensors (DTS / DSS), miniature water pressure gauges or acoustic emission probes, to realize long-term online monitoring of groundwater pressure, temperature changes and structural micro-fracture signals. The monitoring equipment can be deployed by temporary insertion or permanent fixing, and supports plug and play.

[0051] In an optional embodiment, to enhance the functional versatility of the jointed concrete 12, C40 early-strength sulfoaluminate cement concrete can be used, with 0.9% polypropylene fiber and 1.2% steel fiber (13mm in length) added by volume, to achieve: initial setting time ≤45 minutes, 6-hour strength reaching 70% of the design value; crack resistance index increased by 60%, effectively suppressing early plastic shrinkage cracks; and bond strength with SK polyurea layer ≥1.5MPa.

[0052] In addition, crushed stone aggregate with a particle size of 5 to 10 mm can be used, and ecological cementitious agent (geocolitica + lime powder) can be selected as the cementing material. The porosity is controlled at 18% to 22%, and honeycomb grooves are set on the surface.

[0053] During operation, a small amount of seepage water can slowly permeate through the pores to the bottom water collection tank, preventing water accumulation; at the same time, shade-tolerant mosses can be planted on the surface to achieve visual softening and micro-ecological regulation, improving the comfort of personnel during inspections.

[0054] The complete construction process of this system is as follows: 1. Prefabricate the invert arch 8 in the factory, transport it to the construction site and install it in place; 2. Treat the base surface of the prefabricated invert arch joint area: clean, dry, level with acrylic emulsion mortar, apply interface agent, and scrape SK hand-applied polyurea to form an interface agent and hand-applied polyurea surface layer 13; 3. Lay the bottom plate waterstop 3 and fix it initially with stainless steel pressure plate 5; 4. Install the cast-in-place side arch formwork system, with the side arch waterstop 1 built in, and make holes on it for the circumferential reinforcing steel 2 to pass through; 5. Apply steel ring edging to the reserved reinforcing steel hole 6 and inject anti-leakage glue for sealing; 6. Connect the bottom end of the side arch waterstop 1 to the bottom plate waterstop 3 on site by vulcanization to form a closed waterproof ring; 7. Check and compact the waterstop connection area, and pound it to make it fit the base layer; 8. Pre-embed the reducing four-way pipe 15, circumferential drainage pipe 14, and drainage pipe 18 at the water outlet, and tie them to the non-reinforcing steel; 9. 12. Pour and join the concrete, and set a two-way cross slope as designed; 10. Finally, complete the pouring of the whole ring lining structure and enter the curing stage.

[0055] In operation, external groundwater, rainwater infiltration, and surrounding rock fissure water first enter the system through a φ90mm borehole. After being filtered by the reverse filter geotextile to remove fine particles, the water flows sequentially through: a φ75mm radial PVC drainage pipe → a reducing four-way pipe 15 → a φ75mm circumferential PE drainage pipe → a φ75mm PVC outlet drainage pipe → and is discharged to the drainage ditch outside the tunnel. The entire drainage path is completely enclosed within the lining structure, with no exposed leaks, realizing the design concept of external water drainage within the structure and concealing the pipes within the structure, taking into account functionality, safety, and aesthetic quality.

[0056] This invention has achieved significant technological progress through the following innovative design: 1. Achieved full circumferential closure of the circumferential waterstop: Through on-site vulcanization connection of the waterstop between the side arch and the bottom plate, the problem of waterstop interruption at the joint of the precast invert arch was completely solved, eliminating the bottom leakage channel; 2. Ensures structural continuity: By utilizing pre-reserved rebar holes and sealing treatment, the circumferential reinforcing bars do not need to be routed around, thus avoiding stress concentration and improving the mechanical properties of the joint area; 3. Improved bonding reliability of waterstop: Through multi-layer interface treatment (acrylic emulsion mortar + interface agent + SK polyurea), the bonding strength and durability between the base plate waterstop and the substrate are greatly enhanced; 4. The drainage system is concealed and maintainable: all drainage components are embedded, resulting in a neat appearance; the reducing four-way pipe is equipped with a threaded inspection port to support later dredging and maintenance. 5. The drainage system inside the tunnel has been optimized: the jointed concrete is designed with a two-way cross slope to effectively divert local water accumulation and improve the construction and operation environment.

[0057] In summary, the TBM-based concealed drainage system for unpressurized water conveyance tunnels proposed in this invention successfully integrates multiple requirements such as structural safety, reliable waterproofing, efficient drainage, and convenient operation and maintenance. It is particularly suitable for high-standard underground engineering construction scenarios such as long and deep-buried hydraulic tunnels and rail transit tunnels, and has broad prospects for promotion and application.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A concealed drainage and sealing system for a TBM-based unpressurized water conveyance tunnel, characterized in that: include: Precast invert arch (8), cast-in-place side arch (7), water-stop structure and drainage structure; The water-stopping structure consists of a side-top arch water-stopping strip (1) set in the cast-in-place side-top arch (7) and a bottom plate water-stopping strip (3) set on the surface of the precast invert arch (8). The side-top arch water-stopping strip (1) and the bottom plate water-stopping strip (3) are connected by vulcanization to form a continuous closed ring water-stopping system. The drainage structure includes multiple eccentric four-way pipes (15), circumferential drainage pipes (14), and drainage pipes (18) at the outlet holes, which are arranged at intervals along the tunnel axis. The eccentric four-way pipes (15), the circumferential drainage pipes (14), and the drainage pipes (18) at the outlet holes are all pre-embedded in the lining concrete of the cast-in-place side arch (7) and fixed by non-stressed steel bars.

2. The concealed drainage and sealing system for TBM unpressurized water conveyance tunnels according to claim 1, characterized in that, The side arch waterstop (1) is a centrally embedded rubber waterstop with a thickness of 8-12mm and a width of 350-450mm. The bottom end of the side arch waterstop (1) extends into the precast invert arch (8) and is used to connect with the bottom plate waterstop (3) on site by vulcanization.

3. The concealed drainage and sealing system for TBM unpressurized water conveyance tunnels according to claim 1, characterized in that, The edge arch waterstop (1) is provided with a reserved steel bar hole (6) for the circumferential reinforcing steel bar (2) to pass through. The gap between the reserved steel bar hole (6) and the circumferential reinforcing steel bar (2) is sealed by wrapping with a steel ring and using anti-leakage glue.

4. The concealed drainage and sealing system for TBM unpressurized water conveyance tunnels according to claim 1, characterized in that, Each of the circumferential drainage pipes (14) is provided with multiple reducing cross pipes (15) at circumferential intervals. The reducing four-way pipe (15) has an upper branch pipe and a lower branch pipe. The upper branch pipe is connected to the radial drainage flower pipe (16), and the lower branch pipe is detachably connected to an external threaded cap (21).

5. The concealed drainage and sealing system for TBM unpressurized water conveyance tunnels according to claim 1, characterized in that, The bottom plate waterstop (3) is pressed by the stainless steel pressure plate (5) connected to the precast invert arch (8).

6. The concealed drainage and sealing system for TBM unpressurized water conveyance tunnels according to claim 5, characterized in that, The precast invert arch (8), the bottom plate waterstop (3) and the stainless steel pressure plate (5) are filled with jointed concrete (12). The surface of the jointed concrete (12) is provided with a two-way cross slope.

7. A construction method for a concealed drainage and sealing system in a TBM-based unpressurized water conveyance tunnel, characterized in that, Includes the following steps: A bottom plate waterstop (3) is installed on the surface of the precast invert arch (8), and a side arch waterstop (1) is installed inside the cast-in-place side arch (7). The edge arch waterstop (1) and the bottom plate waterstop (3) are connected by vulcanization to form a continuous closed ring waterstop system; Multiple eccentric four-way pipes (15), circumferential drainage pipes (14) and drainage pipes (18) at the water outlet are pre-embedded in the lining concrete of the cast-in-place side arch (7) along the tunnel axis and fixed by non-stressed steel bars.

8. The construction method for the concealed drainage and sealing system of a TBM unpressurized water conveyance tunnel according to claim 7, characterized in that, Also includes: A pre-reserved steel bar hole (6) is provided on the edge arch waterstop (1) for the circumferential reinforcing steel bar (2) to pass through, and is sealed by wrapping with a steel ring and using anti-leakage glue. Multiple reducing four-way pipes (15) are arranged circumferentially in each circumferential drainage pipe (14). Each reducing four-way pipe (15) has an upper branch pipe and a lower branch pipe. The upper branch pipe is connected to the radial drainage flower pipe (16), and the lower branch pipe is detachably connected to an external thread cap (21). The bottom plate waterstop (3) is pressed onto the precast invert (8) by a stainless steel pressure plate (5), and joint concrete (12) is poured on the precast invert (8), the bottom plate waterstop (3) and the stainless steel pressure plate (5), with a two-way cross slope on the surface of the joint concrete (12).

9. The construction method of the concealed drainage system for a TBM-based unpressurized water conveyance tunnel according to claim 7, characterized in that, Before the installation of the bottom plate waterstop (3), the base surface of the precast invert arch (8) is treated. The treatment steps include: The bolt grooves and invert joint areas on the surface of the precast invert (8) are cleaned and dried until they are saturated and dry. Then, acrylic emulsion mortar is used to backfill and smooth the surface. Apply two coats of interface agent to the surface of the precast invert (8) with an interval of ≥3h. After the surface is dry, apply SK hand-scraped polyurea to form an adhesive layer.

10. The construction method of the concealed drainage system for a TBM-based unpressurized water conveyance tunnel according to claim 9, characterized in that, The bottom plate waterstop (3) is laid on the adhesive layer; The waterstop strip (1) on the top arch and the waterstop strip (3) on the bottom plate are connected by vulcanization to form a vulcanized connection part (9) of the waterstop strip. The bottom plate waterstop (3) and the vulcanized connection part (9) of the waterstop are hammered to make the bottom plate waterstop (3) and the vulcanized connection part (9) of the waterstop adhere to the adhesive layer.

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