High-water-pressure tunnel lining back osmometer mounting device, mounting method and maintenance method

Abstract

The invention relates to the technical field of operation high-water-pressure tunnel lining water pressure monitoring systems, and particularly discloses a high-water-pressure tunnel lining back osmometer installation device, an installation method and a maintenance method. The hollow screw in the pile casing integrates five core functions of installation and positioning, drainage and pressure relief, water injection and moisture retention, cleaning and maintenance and equipment replacement, and is matched with a rubber plug, a guide rail strip and a counter-force plate at the hole opening of a drill hole to form a rigid fixing system, and water pressure in the hole is stably conducted into a tunnel lining structure. The osmometer and the rubber plug are effectively prevented from being flushed off due to overhigh water pressure in the hole, and the risk of sealing failure is reduced. According to the overall scheme, the construction safety, the sealing reliability after installation and the maintenance convenience of osmometer installation under the high-water-pressure stratum environment are remarkably improved, and excellent adaptability is shown under the complex geological conditions of high water pressure, high mud content, high calcium content and the like.

Description

Technical Field

[0001] This invention relates to the technical field of water pressure monitoring systems for high water pressure tunnel linings, and more specifically, to an installation device, installation method, and maintenance method for a piezometer installed behind a high water pressure tunnel lining. Background Technology

[0002] In tunnels operating under high water pressure, the groundwater pressure behind the lining is a core load threatening structural safety. Prolonged exposure to high water pressure can easily lead to lining cracking, steel reinforcement corrosion, and accelerated leakage, directly endangering tunnel operational safety. Existing technology utilizes piezometers to monitor water pressure changes in real time, triggering early warnings in cases of abnormal pressure increases and providing crucial data support for emergency response.

[0003] However, the installation of piezometers behind the secondary lining of high-water-pressure tunnels faces multiple technical and safety challenges, including the risk of water jetting, defects in the sealing process, and inconvenience in disassembly and maintenance. Firstly, defects in the sealing process lead to distorted monitoring data: when using early-strength cement to seal the installation holes, the continuous full-water state causes the orifice seal to fail, and the piezometer, under long-term water pressure, is prone to forming seepage channels with the surrounding rock, failing to accurately reflect the stress state of the lining. Secondly, if the area behind the lining is water-rich, high-pressure water jetting can easily occur during drilling or maintenance, not only interfering with normal tunnel operation but also posing a direct threat to construction personnel. Furthermore, existing devices lack maintainability design; after a piezometer malfunctions, the entire device must be removed and replaced, resulting in high maintenance costs and requiring secondary drilling that damages the structure. In addition, piezometers need to operate in a wet environment for extended periods. If changes in the tunnel environment cause the piezometer area to become dry, the piezometer test data can easily show negative pressure, leading to instrument damage. Manual water injection is required to maintain the sensor's moisture, but current traditional installation methods cannot meet this maintenance requirement, necessitating the development of a water injection maintenance function.

[0004] More significantly, installing piezometers in tunnels in the karst region of Southwest China presents unique technical challenges. During drilling, calcareous groundwater reacts with the borehole wall to form calcium carbonate deposits. The rough surface of the inner wall of traditional steel / PVC casings accelerates deposit adhesion, leading to probe entrapment, channel blockage, and instrument damage. Simultaneously, groundwater with high mud content can easily enter the system through the casing's inlet, covering the piezometer's sensing components and causing data anomalies. Existing technologies lack filtration or borehole cleaning devices.

[0005] In summary, existing piezometer installation technologies have systemic defects under conditions of high water pressure, karst development, and complex hydrology. There is an urgent need to develop specialized installation devices and processes with sealing protection, maintainability, and environmental adaptability to fill the technological gap in this field. Summary of the Invention

[0006] The present invention aims to overcome at least one of the shortcomings of the prior art and provides a piezometer installation device, installation method and maintenance method behind the lining of a high water pressure tunnel. It is used to improve the construction safety of piezometer installation in high water pressure strata, the sealing reliability after installation and the convenience of maintenance, and solve the problems of high pressure water jetting during the installation and maintenance of existing devices, failure of orifice seal during long-term use leading to piezometer failure, and inconvenience of maintenance requiring complete removal.

[0007] The technical solution adopted by this invention is to provide a device for installing a piezometer behind the lining of a high-pressure tunnel, comprising: The casing has one open end and the other closed end with a bottom hole. The closed end is filled with permeable geotextile. Except for the open end, the casing is wrapped with geotextile. The casing is installed in the borehole that crosses the secondary lining and initial support of the tunnel, with the open end close to the borehole opening and the closed end extending into the surrounding rock. The hollow screw has a straight head and a curved tail. The screw body has multiple openings. The head is connected to a piezometer and extends into the permeable soil stone at the closed end of the casing. The tail is located outside the casing and is connected to the first drainage pipe, or a plug nut is installed. A first rubber stopper is used to accommodate the hollow screw as it passes through and to seal the open end of the protective sleeve.

[0008] The guide rail has a pre-reserved groove inside and is fixed to the secondary lining of the tunnel around the borehole opening; A reaction plate is inserted into the groove of the guide rail to clamp the hollow screw.

[0009] The functions of each component in the above scheme are as follows: The casing, encasing geotextile and containing permeable geotextile, facilitates the transmission of water pressure in the surrounding rock and the filtration of sediment. The hollow screw integrates the connection and drainage / pressure relief functions of the piezometer. On one hand, it assists in aligning the piezometer with the installation position, ensuring equipment placement accuracy. On the other hand, it discharges accumulated water and releases water pressure in real time through its internal channels, effectively suppressing the threat of high-pressure water jets to tunnel operation and construction personnel during drilling or maintenance. The casing is fitted over the hollow screw, fixing the head of the hollow screw to prevent displacement and protecting the piezometer. Utilizing the dual filtration structure of geotextile and permeable geotextile, it reduces the impact of sediment accumulation on the piezometer from the source. A first rubber plug seals the open end of the casing. The guide rail and reaction plate fix the screw position, ensuring the reaction plate is tightly fitted to the first rubber plug. This stably transmits the water pressure in the hole to the tunnel lining structure, effectively preventing the piezometer and rubber plug from being washed away due to excessive water pressure in the hole, reducing the risk of seal failure, and significantly improving the overall safety during equipment operation. This solution integrates multiple functions such as installation positioning, drainage and pressure relief, and equipment replacement through a hollow screw integrated design that allows for multiple uses. It provides support throughout the entire lifecycle of piezometer installation, long-term operation and maintenance, and fault replacement, simplifying the operation process, improving equipment stability, and effectively ensuring safe and efficient installation operations.

[0010] To further reduce the risk of water jetting, the aforementioned high-water-pressure tunnel lining back piezometer installation device also includes: The protective cover is shaped like a pot lid, with openings in the center and bottom, and a hollowed-out top. Its edges are fixed to the secondary lining of the tunnel, and its center is directly opposite the drill hole and accommodates the hollow screw rod to pass through. The second rubber stopper is used to accommodate the hollow screw as it passes through and to seal the center of the protective cover. The second drain pipe is connected to the lower opening of the protective cover.

[0011] The protective cover covers the borehole opening to form a shield and protect it from the impact of high-pressure water flow on construction personnel; the upper part of the protective cover is hollowed out to facilitate the operation of construction personnel; the edges are fixed and the center and lower part are perforated, which, together with the hollow screw rod - the first drainage pipe and the second drainage pipe, are used to catch seepage water during installation and drain it out through the drainage pipe to avoid it interfering with the normal operation of the tunnel.

[0012] To ensure normal tunnel operation, the protective cover is further reinforced with stainless steel strips along its edges, and these strips are wrapped with water-stop strips. The stainless steel strips enhance the erosion resistance of the protective cover edges, while the water-stop strips improve the sealing performance between the protective cover and the secondary tunnel lining, forming a double seepage barrier to prevent water from seeping into the tunnel and interfering with normal operation.

[0013] To further enhance the seal, a water-stop rubber ring is fitted around the center of the first rubber plug, and both ends are fixed to the hollow screw by nuts. The water-stop rubber ring enhances the fit between the first rubber plug and the inner wall of the borehole, strengthening the sealing effect, while the nuts ensure that the rubber plug remains stable and does not shift.

[0014] To further address the equipment misalignment issue, the reaction plate is designed as a two-sided splicing structure, with a boss on one side and a matching groove on the other. The two sides are then joined and secured with bolts. This allows the reaction plate to be precisely inserted into the guide rail slots, ensuring a stable structure after tightening and effectively clamping the hollow screw to guarantee positioning accuracy. This solves the technical problem of equipment misalignment caused by water pressure in traditional installations.

[0015] Furthermore, the fastening bolts include side fastening bolts and front fastening bolts, which are used to press the hollow screw on both sides and to make the reaction plate fit tightly against the secondary lining of the tunnel, respectively.

[0016] To facilitate installation and disassembly, pull rings are provided at one end on both sides of the reaction plate. These pull rings allow operators to apply force to quickly install and remove the reaction plate, improving ease of maintenance or replacement and meeting the technical requirements for regular maintenance in long-term piezometer monitoring.

[0017] To stabilize the piezometer signal transmission, both the first rubber stopper and the reaction plate are further provided with cable holes. The piezometer cable is fixed to the hollow screw and extends through the cable holes. The cable holes regulate the cable routing, preventing tangling and compression, and fixing the cable reduces the impact of shaking on the sealing structure, ensuring signal transmission stability.

[0018] To further reduce the clogging rate, the inner wall and bottom hole of the casing are polished to a roughness of ≤0.8 μm. Polishing reduces the roughness of the inner wall and bottom hole, significantly reducing the probability of calcium carbonate deposits and fine particles adhering to the casing, minimizing the risk of siltation inside the casing, and ensuring smooth water pressure transmission between the piezometer and the surrounding rock. This is an optimized design specifically for the high-mud-content and high-calcium-content groundwater environment in the karst region of Southwest China. In one or more embodiments of the present invention, the casing is made of tempered glass, and the clogging rate is significantly reduced after polishing, solving the technical defect that the inlet hole of traditional steel / PVC casings is easily clogged by silt.

[0019] Furthermore, the closed end of the casing is wrapped with multiple layers of geotextile. The multiple layers of geotextile enhance the filtration capacity of the closed end, allowing water pressure to pass through while preventing fine particles from the surrounding rock from entering and clogging the permeable geotextile, thus protecting the piezometer sensing element.

[0020] Another object of the present invention is to provide an installation method for the aforementioned high water pressure tunnel lining back piezometer installation device, comprising the following steps: S1. Design and assemble the casing and hollow screw: Conduct a site survey to select the piezometer installation location, design the drilling depth, and customize accessories; install the permeable geotextile to the closed end of the casing, and wrap the outer wall of the casing with geotextile; install the first rubber plug, the second rubber plug, and the piezometer onto the hollow screw, insert the head of the hollow screw into the permeable geotextile at the closed end of the casing, and install the first drainage pipe to the tail of the hollow screw; S2. Drilling and installing a piezometer: Fix the guide rail to the secondary tunnel lining with bolts, with the groove of the guide rail facing upwards; fix the protective cover to the secondary tunnel lining, with the center facing the drill hole, and open the bottom to connect the second drainage pipe; pass the drill rod through the center opening of the protective cover, and after confirming that the hole depth is qualified, insert the assembled casing and hollow screw into the hole until the first rubber plug is tightly attached to the hole opening and there is no water leakage, and use the second rubber plug to seal the middle opening of the protective cover; S3. Install the reaction plate and remove the protective cover: Place the reaction plate along the guide rail, pass the piezometer cable through the cable hole, splice the two sides of the reaction plate and fix it with fastening bolts, so that the two sides of the reaction plate are clamped to the hollow screw and the front is close to the secondary lining of the tunnel; remove the protective cover, remove the first drainage pipe at the tail of the hollow screw and install the plug nut, and the piezometer installation is complete.

[0021] Furthermore, both the first and second rubber plugs are fixed to the hollow screw rod with nuts; the piezometer is tied to the head of the hollow screw rod and wrapped with geotextile.

[0022] Another objective of this invention is to provide a maintenance method for the aforementioned high-pressure tunnel lining backfill piezometer installation device: When the area behind the secondary tunnel lining is in a dry state for a long period, to prevent damage to the piezometer due to prolonged dryness, the plug nut of the hollow screw is unscrewed, and water is slowly injected into the hole through the hollow screw to keep the piezometer continuously moist. After water injection, the plug nut is tightened. When changes occur in the surrounding environment of the tunnel, causing the area behind the tunnel lining to remain dry for a long period, active water injection maintains a moist environment for the piezometer, preventing sensor failure due to prolonged dryness, extending equipment lifespan, ensuring continuous monitoring data, and filling the technical gap where traditional installation methods cannot achieve sensor maintenance.

[0023] Another objective of this invention is to provide a maintenance method for the aforementioned high-pressure tunnel lining backfill piezometer installation device: To prevent blockage of the hollow screw and piezometer, the plug nut of the hollow screw is periodically unscrewed to observe the water flow; if blockage is present, a high-pressure water gun is used to inject water through the opening in the hollow screw and rod body to clean the borehole wall and piezometer. After cleaning, a first drain pipe is connected to the tail of the hollow screw for drainage, and the plug nut is tightened after drainage. Regular inspection combined with high-pressure cleaning promptly removes blockages and restores drainage and pressure relief functions, preventing piezometer malfunction due to blockage and ensuring long-term monitoring effectiveness, especially suitable for groundwater environments with high calcium and high mud content.

[0024] Another objective of this invention is to provide a method for replacing a piezometer behind a high-pressure tunnel lining, comprising the following steps: first, installing a protective cover; then, unscrewing the fastening bolts; next, unscrewing the plug nut of the hollow screw rod; connecting the first drainage pipe and draining it to the roadside ditch; then, pulling out the reaction plate using a pull ring; subsequently, using the hollow screw rod, pulling out the piezometer and the first rubber plug together; finally, completing the installation of the new piezometer according to the above installation method. When the piezometer needs to be replaced due to a malfunction, there is no need to disassemble the original installation structure; the old equipment can be directly and conveniently pulled out of the hole using the hollow screw rod, significantly shortening the replacement period, reducing operational difficulty, and significantly reducing manpower and time costs during operation and maintenance.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides an installation device, installation method, and maintenance method for a piezometer behind the lining of a high-water-pressure tunnel. It achieves stable transmission of water pressure and filtration of sediment in the surrounding rock through a combination of a casing and geotextile / permeable stone. The hollow screw integrates five core functions: installation positioning, drainage and pressure relief, water injection and moisturizing, cleaning and maintenance, and equipment replacement. Combined with guide rails and reaction plates, it forms a rigid fixing system, significantly improving the construction safety, post-installation sealing reliability, and maintenance convenience of the piezometer installation in high-water-pressure strata environments. Furthermore, the protective cover and double-layer rubber plug design effectively suppress high-pressure water jets that could injure construction personnel; the stainless steel strip and waterstop strip provide a double barrier to prevent water seepage from interfering with tunnel operation; the polished inner wall of the casing and multi-layer geotextile wrapping significantly reduce the risk of blockage by calcium deposits in karst areas; cable holes ensure stable signal transmission; and the guide rail slots and reaction plate pull ring structure simplify the maintenance process. The overall solution, through its integrated "one rod, multiple uses" design, solves the systemic defects of existing piezometer installation methods, such as water flow impact, sealing failure, and maintenance difficulties. It also demonstrates excellent adaptability under complex geological conditions such as high water pressure, high mud content, and high calcium content. Attached Figure Description

[0026] Figure 1 This is a flowchart of the implementation steps of the present invention.

[0027] Figure 2 Schematic diagram of piezometer installation and protection device.

[0028] Figure 3 This is a schematic diagram of the installation plane of the guide rail and the reaction plate.

[0029] Figure 4 This is a three-dimensional schematic diagram of the reaction plate structure.

[0030] Figure 5 This is a three-dimensional schematic diagram of the guide rail structure.

[0031] Figure 6This is a schematic diagram of the hollow screw and casing after assembly.

[0032] Figure 7 This is a schematic diagram of the protective shield.

[0033] Labeling Explanation: 01 Reaction Plate, 02 Guide Rail, 03 Fastening Bolt, 04 Reaction Plate Pull Ring, 05 Protective Cover, 06 Hollow Screw, 07 Plug Nut, 08 First Rubber Plug, 09 Water-Stop Rubber Ring, 10 Drill Hole, 11 Tempered Glass Casing, 12 Permeable Geotextile, 13 Permeable Geotextile Stone, 14 Second Drainage Pipe, 15 Tunnel Secondary Lining, 16 Tunnel Initial Support, 17 Surrounding Rock, 18 Second Rubber Plug, 19 First Drainage Pipe. Detailed Implementation

[0034] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0035] like Figures 1-7 As shown in the figure, this embodiment provides an installation device, installation method, and maintenance method for a piezometer behind the lining of a high-pressure tunnel. The steps are as follows: 1) Construction preparation Site surveys were conducted to select the installation location 10 for the piezometer, and the position of each fixing point was marked. Based on the thickness and dimensions of the secondary lining 15 and the initial support 16 of the tunnel provided in the as-built documentation, the drilling depth 10 was designed. The drilling depth should take into account over- and under-excavation during construction and can be appropriately increased by 20-30cm. Customized accessories including reaction plates 01, guide rails 02, fastening bolts 03, reaction plate pull rings 04, protective covers 05, hollow screws 06, plug nuts 07, first rubber plugs 08, water-stop rubber rings 09, tempered glass casings 11, permeable geotextiles 12, permeable geotextile stones 13, and second drainage pipes 14 were prepared. On-site construction personnel and drilling equipment were ready. A pre-drilled hole was reserved at the bottom of the tempered glass casing 11, with a diameter not less than 10mm and sufficient smoothness.

[0036] 2) Assemble the tempered glass casing 11 The core objective of the casing 11 is to "protect the piezometer and reduce deposits inside the borehole". It is made of tempered glass with high smoothness (inner wall roughness ≤0.8μm) and high strength (compressive strength ≥80MPa). Its inner wall and the bottom opening wall need to be polished to reduce the adhesion of calcium carbonate and fine particulate deposits from the source. The outer diameter of the casing 11 needs to be 4-8mm smaller than the borehole diameter (e.g., if the borehole diameter is 60mm, the outer diameter of the casing should be 52-56mm) to leave an installation gap and ensure that there is no jamming when it is inserted into the borehole.

[0037] First, take a custom-sized permeable geotextile stone 13 and align it with the preset installation position at the bottom of the casing 11. Slowly insert it and gently press it until the permeable stone 13 is completely flush with the installation position. Then, cut a permeable geotextile 12 that matches the length and circumference of the casing 11 (the width should cover the outer circumference of the casing + 2cm overlap), and wrap it around the casing, gently pressing it together by hand during the wrapping process. After wrapping, secure it with a water-resistant cable tie at the top, middle, and bottom of the casing. The bottom of the casing 11 can be wrapped with multiple layers of geotextile 12 to protect the casing and improve the filtration capacity of the particles. After wrapping, visually inspect it to ensure that the geotextile is wrinkle-free and gap-free, that the wrapped surface is not loose when rubbed by hand, and that the cable ties are not misaligned.

[0038] 3) Assemble the piezometer installation device Install the rubber stopper into the designated position corresponding to the orifice of the hollow screw, with a water-stopping rubber ring fitted over the middle of the rubber stopper, and tighten both ends with nuts. Next, tie the piezometer to the bottom of the hollow screw and wrap it with geotextile, simultaneously fixing its cable to the screw. Then, slowly insert the hollow screw with the piezometer assembled into the prepared tempered glass casing, ensuring that the bottom of the screw accurately engages with the central groove of the permeable geotextile stone inside the casing. Finally, install the first drainage pipe to the end of the hollow screw.

[0039] Step 1: Install the first rubber plug 08. First, take a suitable water-stop rubber ring 09 (with a cross-sectional diameter ≥ 10mm) and evenly place it inside the middle of the first rubber plug 08, ensuring that the rubber ring 09 is not twisted. Then, hold the first rubber plug 08 and align it with the preset installation position of the corresponding hole of the hollow screw 06. Slowly push it in until the end face of the first rubber plug 08 is flush with the hole. Then, take two stainless steel nuts (matched according to the screw thread specifications) and put them on the screw from both ends of the first rubber plug 08 and tighten them clockwise. The first rubber plug 08 is now installed.

[0040] Step 2: Install the piezometer: Take the piezometer (not shown in the diagram), with the sensing end facing down, and tie it to the head of the hollow screw 06 (5-8 cm from the end of the screw) using wide, water-resistant nylon cable ties. Next, completely wrap the piezometer from the sensing end to the cable tie on the screw, and then tie a slipknot at each end with thin nylon thread. Then, arrange the piezometer's signal cable straight along the side wall of the hollow screw 06, using narrow nylon cable ties every 20 cm. Finally, tidy up the piezometer's signal cable and thread it through the pre-drilled hole inside the first rubber stopper 08.

[0041] The third step is to insert the hollow screw 06 into the tempered glass sleeve 11: Insert the bottom of the screw 06 into the sleeve 11, visually aligning it with the central groove of the permeable stone 13 during insertion to avoid the side wall of the screw 06 scraping against the inner wall of the sleeve 13. When the head of the hollow screw 06 is fully inserted into the central groove of the permeable stone 13 (you will feel a slight sticking sensation), stop inserting. At this point, observe the connection between the first rubber stopper 08 and the opening of the sleeve 11, ensuring that the outer side of the first rubber stopper 08 is completely flush with the end face of the opening of the sleeve 11, without any offset or gaps.

[0042] Step 4: Install the second drain pipe 14: Take the second drain pipe 14 (length according to the on-site wiring requirements) with an inner diameter that matches the end interface of the hollow screw. First, apply a layer of polytetrafluoroethylene sealing tape evenly to the external thread at the end of the screw (wrap 5-6 turns, in the same direction as the thread). Then, align the hose connector (internal thread) with the end interface of the screw and tighten it clockwise by hand until it cannot be turned.

[0043] 4) Install guide rail 03 Following the design drawings, first accurately draw the longitudinal installation center line of the guide rail 03 and the positions of the transverse fixing points at both ends on the secondary lining surface. Ensure that the drawn center line is parallel to the axis of the piezometer mounting hole 10. Set the distance between the fixing points according to the design specifications, and mark a cross at each fixing point using an oil-based marker.

[0044] Next, drill a hole vertically at the center of the marked "cross". After drilling, insert the expansion bolt tube and bolt shank into the hole in sequence, and tighten the nut clockwise with a torque wrench to ensure that the flat washer and spring washer are completely in contact with the secondary lining surface, avoiding any loose gaps.

[0045] After all bolts are in place, attach the guide rail 03 tightly to the secondary lining surface, aligning it with the pre-drawn center line. Note that the end of the guide rail with the end cap should face downwards to ensure that the bolt holes on the guide rail accurately align with the expansion bolts. Then, insert flat washers and spring washers onto each bolt and tighten the nuts.

[0046] For environments where high water pressure is expected, the strength of the bolts and the 03 steel plate of the guide rail must be verified to ensure that the safety factor is not less than 1.5 under normal use conditions.

[0047] 5) Install protective cover 05 The protective cover 05 is fixed to the secondary lining concrete 15 using a nail gun or expansion bolts, with its center aligned with the borehole 10. The lower opening is connected to the second drainage pipe 14, which can drain the water from the borehole to the roadside ditch or water ditch.

[0048] 6) Drilling The operator holds a down-the-hole drill, inserts one end of the drill rod through the center hole of the protective cover 05, aligns it with the crosshair positioning mark at hole position 10, and after adjusting the angle, starts the drill to begin drilling. Once the designed hole depth is reached, the down-the-hole drill is shut off, the drill rod is removed, and the drilling depth is measured with a tape measure. Drilling is complete once the required depth is met. If the water flow in the hole is large (the water flow is jet-like or continuously gushing), the center hole of the protective cover can be temporarily sealed with the first rubber plug 08.

[0049] 7) Install piezometer Inspect the assembled hollow screw 06 (including piezometer, geotextile, cable, and casing) for damage, ensure the geotextile is secure, and confirm the cable is firmly fixed. Confirm the piezometer is functioning correctly. After confirming the first drainage pipe connection at the end of the hollow screw 06 is secure, remove the second rubber plug 18 from the protective cover. Insert the assembled hollow screw 06 and casing 11 into the borehole 10, ensuring the second rubber plug 18 is tightly fitted to the borehole opening to prevent leakage. Simultaneously, lead the first drainage pipe connected to the end of the hollow screw 06 to the roadside drainage ditch. The bend of the hollow screw 06 should face the side towards the borehole 10 to prevent water jets from directed towards personnel or the road surface when disassembling the flexible metal water pipe 14.

[0050] 8) Install reaction plate 02 Using the lifting ring 04, slowly insert the reaction plate 02 along the guide rail 03 until the reaction plate 02 is in contact with the end plate of the guide rail 03. The piezometer cable passes through the corresponding hole in the reaction plate 02. Push the right reaction plate 02 towards the left plate, so that the protrusion of the right plate slowly embeds into the groove of the left plate. Install the side and front fastening bolts 03. By adjusting the length of the bolts, ensure that the openings of the left and right reaction plates 02 clamp the hollow screw 06 together, and that the front of the reaction plate 02 is tightly against the secondary lining concrete 15 wall surface. Finally, tighten the nut on the hollow screw 06 to press the reaction plate firmly.

[0051] 9) After the reaction plate 02 is installed, remove the first drain pipe at the end of the hollow screw 06 and install the end cap 07 at the end of the hollow screw 06. When installing the end cap 07, first slowly screw it in clockwise by hand, then use pipe wrenches to tighten it until the end face of the nut is completely in contact with the end face of the screw interface, and then tighten it an additional 1 / 4 turn to ensure that the sealing strip is fully compressed to form an effective seal.

[0052] 10) After checking that the plug nut 07 and the reaction plate 02 are not loose and that the reaction plate bolts are not missing, remove the protective cover 05. The piezometer installation is complete. When removing the protective cover 05, first use a claw hammer to gently pry the nail head (apply force slowly from the nail side to avoid hammering the tempered glass). After the nail is loosened, use needle-nose pliers to clamp the nail head and pull it out.

[0053] 11) Routine maintenance When changes occur in the surrounding environment of the tunnel, causing the back of tunnel linings 15 and 16 to remain in a dry state for an extended period, the following procedure can be followed: First, unscrew the plug nut 07 of the hollow screw 06. Slowly inject clean water into the borehole through the inner hole of the hollow screw 07. The water injection process should be kept stable and uniform to avoid water flow impact causing damage to the piezometer. Inject water until the medium surrounding the piezometer is fully wetted, ensuring that its sensing element is always in the humid environment required for normal operation. After water injection is completed, tighten the plug nut 07 promptly to seal the orifice and prevent debris from entering or water from evaporating too quickly.

[0054] In tunnel environments with high groundwater calcium content or turbid water, calcium deposits or siltation can easily form inside the casing 11 of borehole 10, affecting the normal operation of the piezometer and drainage. Therefore, a regular inspection and maintenance mechanism should be established: periodically unscrew the plug nut 07 of the hollow screw 06, observe the water flow, and determine if there is any blockage.

[0055] If poor water flow or a significant reduction in water output is observed, it indicates that blockage may have occurred on the borehole wall or around the piezometer. In this case, a high-pressure water gun should be connected to the hollow screw 06 to perform reverse flushing through its internal channels and openings on the screw body. During the flushing process, the high-pressure water flow should thoroughly wash the borehole wall, the piezometer surface, and the permeable geotextile 13 to effectively remove sediment and silt, restoring the permeability of the borehole 10.

[0056] After cleaning, connect the end of the hollow screw 06 to the first drain pipe to ensure that the wastewater generated during flushing can be smoothly discharged into the roadside ditch or designated drainage system, preventing water accumulation from affecting the tunnel structure or driving safety. After drainage is completed, check again whether the threaded interface is clean, and reinstall and tighten the plug nut 07 to ensure reliable system sealing.

[0057] By implementing the above-mentioned regular maintenance and emergency response measures, the service life of the piezometer can be effectively extended, the continuity and accuracy of monitoring data can be ensured, and the normal operation of the entire seepage monitoring system can be maintained.

[0058] 12) Equipment replacement When a piezometer needs to be replaced due to malfunction or reaching the end of its service life, the following steps should be strictly followed to ensure safe operation, effective waterproofing, and the continuity and sealing of the monitoring system: Install the protective cover 05: First, install the protective cover 05 onto the secondary lining concrete 15, ensuring its center is aligned with the borehole position 10. The installation of the protective cover effectively prevents groundwater splashing or impurities from entering the borehole during the replacement process, while also providing an interface for subsequent drainage operations.

[0059] Establish a drainage channel: Unscrew the plug nut 07 at the end of the hollow screw 06, connect the first drainage pipe to the end of the hollow screw 06, and lead the drainage pipe to the roadside ditch or designated drainage facility to ensure that groundwater that may seep out during the extraction process can be discharged in a timely and orderly manner to avoid water accumulation or pollution in the tunnel.

[0060] Disassemble the fixing components: Use appropriate tools to unscrew the fastening bolts 03 of the fixing reaction plate 02 to release its mechanical constraint on the system.

[0061] Dismantle the reaction system: Apply force smoothly through the pull ring 04 to pull the reaction plate 02 out of the orifice as a whole.

[0062] Remove the old piezometer: Using the hollow screw 06 as a traction rod, securely connect it to the piezometer body and the first rubber plug 08 at the front end. Slowly and evenly pull the original piezometer assembly out of the borehole. Carefully observe for any obstructions or foreign objects during the extraction process to prevent equipment from remaining in the hole.

[0063] Cleaning and Inspection: After removing the old equipment, the inside of the borehole should be inspected. If necessary, use high-pressure water or compressed air to clean the borehole walls to ensure there is no silt, deposits, or residue, and to keep the borehole unobstructed. At the same time, check the condition of the hollow screw, sealing structure, and surrounding concrete to confirm that they meet the conditions for reinstallation.

[0064] Installing new equipment: After replacing the piezometer with a new one, reinstall the piezometer according to the original piezometer installation procedure.

[0065] Functional verification: After the new equipment is installed, a power-on test and initial data reading should be performed to confirm that the signal transmission is normal and to observe whether the drainage system is unobstructed, ensuring that the entire monitoring device operates stably and is well sealed.

[0066] This embodiment provides an installation device, installation method, and maintenance method for a piezometer behind the lining of a high-pressure tunnel. It has six core advantages: "dedicated adapter, simplified structure, safety and reliability, convenient installation, easy maintenance, and replaceability". It can effectively ensure the safety of the construction process, significantly extend the service life of the piezometer, and effectively control the overall cost from multiple aspects such as equipment replacement and maintenance management, thus completely solving the pain points of traditional installation methods.

[0067] The key structure and specific functions of the device are as follows: (1) The combination design of the protective cover with drainage pipe and the hollow screw can timely drain the pressurized groundwater in the borehole during drilling and installation operations. On the one hand, it can avoid the safety threat of pressurized groundwater to the workers, and on the other hand, it can prevent pressurized groundwater from spraying onto the road surface and affecting road traffic safety, thereby greatly improving the safety of on-site operations. The hollow screw adopts a "one rod, multiple uses" integrated design, integrating five core functions: installation positioning, drainage and pressure relief, water injection and moisturizing, cleaning and maintenance, and equipment replacement. It provides support for the entire cycle from piezometer installation and construction to long-term operation and maintenance and fault replacement, simplifying the operation process and ensuring equipment stability in all aspects.

[0068] ① Installation Phase: Dual Protection for Construction Safety through Positioning and Pressure Relief. During the installation of the piezometer, the hollow screw can simultaneously achieve two key functions: on the one hand, it assists in aligning the piezometer with the installation position, ensuring the accuracy of equipment placement; on the other hand, it discharges accumulated water in the hole and releases water pressure in real time through its internal channels, avoiding safety hazards caused by sudden increases in water pressure during installation. This dual function effectively ensures the safety and efficiency of the installation operation.

[0069] ② Operation Phase: After entering the operation and monitoring phase, the hollow screw serves as both an inspection hole and a water injection hole. On the one hand, water is promptly replenished into the borehole through the screw's water injection hole to ensure that the piezometer is always in a stable and humid working environment, thus preventing sensor failure or equipment damage caused by prolonged dryness. On the other hand, high-pressure water (the water pressure should be less than the piezometer's range) can be injected into the borehole through the internal channels of the screw to specifically flush away calcium carbonate deposits, fine particulate deposits, and impurities on the piezometer surface, effectively clearing the borehole walls and preventing abnormal water pressure data caused by blockage.

[0070] ③ Replacement stage: When the piezometer needs to be replaced due to malfunction, there is no need to disassemble the original installation structure. The old equipment can be directly and conveniently pulled out of the hole with the help of the hollow screw, which greatly shortens the replacement period, reduces the difficulty of operation, and significantly reduces the manpower and time costs in the operation and maintenance process.

[0071] (2) The system consisting of the reaction plate and the guide rail can ensure that the reaction plate fits tightly against the rubber plug. At the same time, with the help of this system, the water pressure in the hole can be stably transmitted to the inside of the tunnel lining structure, effectively preventing the pressure gauge and rubber plug from being washed away due to excessive water pressure in the hole, and significantly improving the overall safety of the equipment during operation.

[0072] (3) A tempered glass casing is installed inside the borehole wall. This casing has the dual advantages of high smoothness and high strength: on the one hand, the smooth inner wall can significantly reduce the probability of calcium carbonate deposits and fine particles adhering to the casing, reducing the risk of sedimentation inside the borehole; on the other hand, the high-strength material can effectively protect the piezometer. At the same time, a permeable stone is installed at the bottom of the casing, and non-woven fabric is wrapped around the permeable stone to form a dual filtration structure: the non-woven fabric can preferentially intercept some fine particles in the water, while the permeable stone further enhances the filtration effect. The synergistic effect of the two can significantly reduce solid impurities entering the borehole, reducing the accumulation of deposits on the borehole wall and the surface of the piezometer from the source.

[0073] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A device for installing a piezometer behind the lining of a high-pressure tunnel, characterized in that, include: The casing has one open end and the other closed end with a bottom hole. The closed end is filled with permeable geotextile. Except for the open end, the casing is wrapped with geotextile. The casing is installed in the borehole that crosses the secondary lining and initial support of the tunnel, with the open end close to the borehole opening and the closed end extending into the surrounding rock. The hollow screw has a straight head and a curved tail. The screw body has multiple openings. The head is connected to a piezometer and extends into the permeable soil stone at the closed end of the casing. The tail is located outside the casing and is connected to the first drainage pipe, or a plug nut is installed. A first rubber stopper is used to accommodate the hollow screw as it passes through and to seal the open end of the protective sleeve. The guide rail has a pre-reserved groove inside and is fixed to the secondary lining of the tunnel around the borehole opening; A reaction plate is inserted into the groove of the guide rail to clamp the hollow screw.

2. The device for installing a piezometer behind a high-pressure tunnel lining according to claim 1, characterized in that, Also includes: The protective cover is shaped like a pot lid, with openings in the center and bottom, and a hollowed-out top. Its edges are fixed to the secondary lining of the tunnel, and its center is directly opposite the drill hole and accommodates the hollow screw rod to pass through. The second rubber stopper is used to accommodate the hollow screw passing through and to seal the center of the protective cover; The second drain pipe is connected to the lower opening of the protective cover.

3. The device for installing a piezometer behind a high-pressure tunnel lining according to claim 1, characterized in that, The first rubber stopper has a water-stopping rubber ring fitted in the middle, and both ends are fixed to the hollow screw by nuts.

4. The device for installing a piezometer behind a high-pressure tunnel lining according to any one of claims 1 to 3, characterized in that, The reaction plate is a two-sided splicing structure, with a boss on one side and a matching groove on the other side. The two sides are spliced ​​together and fixed by fastening bolts.

5. A piezometer installation device behind high water pressure tunnel lining according to any one of claims 1 to 3, characterized in that, Both the first rubber stopper and the reaction plate are provided with cable holes, and the cable of the piezometer is fixed to the hollow screw and extends through the cable holes.

6. A piezometer installation device behind high water pressure tunnel lining according to any one of claims 1 to 3, characterized in that, The inner wall and bottom hole of the casing are polished, with a roughness of ≤ 0.8 μm.

7. The installation method of the high water pressure tunnel lining back piezometer installation device according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Design and assemble the casing and hollow screw: Conduct a site survey to select the piezometer installation location, design the drilling depth, and customize accessories; install the permeable geotextile to the closed end of the casing, and wrap the outer wall of the casing with geotextile; install the first rubber plug, the second rubber plug, and the piezometer onto the hollow screw, insert the head of the hollow screw into the permeable geotextile at the closed end of the casing, and install the first drainage pipe to the tail of the hollow screw; S2. Drilling and installing a piezometer: Fix the guide rail to the secondary tunnel lining with bolts, with the groove of the guide rail facing upwards; fix the protective cover to the secondary tunnel lining, with the center facing the drill hole, and open the bottom to connect the second drainage pipe; pass the drill rod through the center opening of the protective cover, and after confirming that the hole depth is qualified, insert the assembled casing and hollow screw into the hole until the first rubber plug is tightly attached to the hole opening and there is no water leakage, and use the second rubber plug to seal the middle opening of the protective cover; S3. Install the reaction plate and remove the protective cover: Place the reaction plate along the guide rail, pass the piezometer cable through the cable hole, splice the two sides of the reaction plate and fix it with fastening bolts, so that the two sides of the reaction plate are clamped to the hollow screw and the front is close to the secondary lining of the tunnel; remove the protective cover, remove the first drainage pipe at the tail of the hollow screw and install the plug nut, and the piezometer installation is complete.

8. The device for installing a piezometer behind a high-pressure tunnel lining according to claim 7, characterized in that, The first and second rubber plugs are both fixed to the hollow screw rod with nuts; the piezometer is tied to the head of the hollow screw rod and wrapped with geotextile.

9. A maintenance method for the piezometer installation device behind the high water pressure tunnel lining as described in any one of claims 1 to 6, characterized in that, When the area behind the secondary lining of the tunnel is in a dry state for a long time, in order to prevent the piezometer from being damaged due to prolonged dryness, unscrew the plug nut of the hollow screw and slowly inject water into the hole through the hollow screw to keep the piezometer continuously moist. After the water injection is completed, tighten the plug nut.

10. A maintenance method for the piezometer installation device behind the high water pressure tunnel lining as described in any one of claims 1 to 6, characterized in that, To prevent blockage of the hollow screw and piezometer, periodically unscrew the plug nut of the hollow screw and observe the water flow. If blockage is found, use a high-pressure water gun to inject water through the opening in the hollow screw and the rod body to clean the borehole wall and piezometer. After cleaning, connect the first drain pipe to the tail of the hollow screw to drain the water. After draining, tighten the plug nut.

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