A long-term monitoring and depressurization system for water pressure behind tunnel lining during operation

Abstract

This invention discloses a long-term monitoring and pressure relief system for water pressure behind tunnel lining during operation, belonging to the field of tunnel engineering safety monitoring technology. The system includes a monitoring subsystem, a pressure relief subsystem, and a data transmission and control module. The monitoring subsystem embeds a piezometer between the primary support and secondary lining at key sections of the high-pressure, water-rich tunnel section, and works with structural stress-strain sensors to achieve long-term automated monitoring of multiple parameters. The pressure relief subsystem deploys permanent pressure relief holes penetrating from the secondary lining to behind the primary support at the bottom of the tunnel cable trench, and uses an openable / closable device to drain excess pressure. The data transmission and control module receives monitoring data, analyzes and issues early warnings, and coordinates with the pressure relief subsystem to perform proactive intervention. This invention forms an integrated "prevention-monitoring-treatment" solution, effectively avoiding lining defects caused by water pressure accumulation. It features simple structure, low operation and maintenance costs, and high safety and reliability, and is suitable for waterproofing and pressure protection throughout the entire life cycle of tunnels during operation.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering safety monitoring technology, specifically relating to a long-term monitoring and depressurization system for water pressure behind the tunnel lining during the tunnel operation period. Background Technology

[0002] In tunnel engineering, even after grouting and water-blocking treatment in the breakthrough section, small cracks may still remain behind the lining. During operation, groundwater tends to slowly accumulate along these cracks, gradually forming a high-pressure environment. Over the long term, this high water pressure will continuously compress the tunnel lining structure, potentially leading to lining cracking, spalling, or even structural instability, seriously threatening the safety of tunnel operation.

[0003] In existing technologies, monitoring of water pressure behind tunnel linings is mostly concentrated during the construction phase, employing short-term manual monitoring methods. This results in insufficient monitoring frequency and continuity, failing to cover long-term risks during operation. Furthermore, there is a lack of active pressure relief measures to complement the monitoring, relying solely on water-blocking methods during construction, which are insufficient to address the problem of water pressure accumulation during operation. Once the water pressure exceeds the lining's bearing capacity, passive repairs are often the only option, leading to high repair costs and disruptions to normal tunnel operation. Therefore, an integrated system capable of coordinating long-term water pressure monitoring and active pressure relief during operation is needed to fill this technological gap. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an integrated long-term monitoring and pressure relief system that combines prevention, monitoring, and treatment. This system enables long-term stable monitoring of water pressure, intelligent early warning of overpressure, and proactive pressure relief measures for water pressure behind the tunnel lining during its operational period.

[0005] The objective of this invention is achieved through the following technical solution: A long-term monitoring and pressure relief system for water pressure behind tunnel lining during operation includes a monitoring subsystem, a pressure relief subsystem, and a data transmission and control module. The monitoring subsystem continuously monitors the water pressure behind the tunnel lining and the stress-strain state of the support structure. The pressure relief subsystem actively drains accumulated water to control the water pressure when it exceeds a safety threshold. The data transmission and control module receives monitoring data from the monitoring subsystem, analyzes and processes it, triggers an early warning, and coordinates with the pressure relief subsystem to perform pressure relief operations. The monitoring subsystem includes multiple monitoring sections spaced longitudinally along the tunnel. Each monitoring section has a piezometer pre-embedded between the initial support and the secondary lining, and each monitoring section is also equipped with a sensor assembly for monitoring structural stress and strain.

[0006] The monitoring sections are selected from the key mileages of the high-pressure, water-rich sections of the tunnel. A total of 65 measuring points are set up on each monitoring section, covering the key stress areas of the lining.

[0007] The sensor assembly includes embedded strain gauges and rebar gauges; the embedded strain gauges are used to monitor the stress of the initial support concrete and the secondary lining concrete; the rebar gauges are used to monitor the stress of the steel frame and the stress of the secondary lining rebars; two measuring points are arranged at each of the seven locations (arch crown, left and right arch waists, left and right arch feet, left and right sidewalls) of each monitoring section; and one measuring point is arranged at each of the nine locations (arch crown, left and right arch waists, left and right arch feet, left and right sidewalls, left and right inverted arches, and right inverted arches) of each section for water seepage pressure monitoring.

[0008] The pressure relief subsystem includes permanent pressure relief holes arranged longitudinally along the tunnel; the permanent pressure relief holes penetrate the secondary lining to the back of the initial support, with a hole spacing of 5-10m, which can be dynamically adjusted according to the actual seepage volume of the tunnel; the opening of the permanent pressure relief holes is equipped with an openable and closable device; the openable and closable device is a manually operated protective cover or an automatic control valve linked to the data transmission and control module.

[0009] The data transmission and control module includes an automated integrated testing system, which consists of an automatic data acquisition subsystem, a remote data transmission subsystem, and a data management and analysis subsystem. The automatic data acquisition subsystem can be connected to vibrating wire sensors, inductive sensors, and temperature sensors to achieve unattended automatic data acquisition. The remote data transmission subsystem supports at least one communication method among RS485 bus, fiber optic, wireless data transmission, or GPRS. The data management and analysis subsystem can plot temporal curves of monitoring data, perform regression analysis, and trigger early warnings when data exceeds thresholds.

[0010] The technical parameters of the automated integrated testing system are as follows: strain measurement range is ±1500με, steel bar stress measurement range is ±300MPa, pressure measurement range is 0~5000kN, applicable ambient temperature is -10°C~+50°C, and it is powered by AC 220V / 50Hz power supply.

[0011] The monitoring subsystem can also be extended to connect to surface crack gauges and string surface strain gauges; when cracks or abnormal surface stress occur in the secondary lining of the tunnel, the surface crack gauges are used to monitor the development of cracks, and the string surface strain gauges are used to monitor the surface stress state of the lining.

[0012] The monitoring frequency of the monitoring subsystem is set according to the phases: during the construction period, a combination of manual and automated monitoring is adopted. The frequency of manual monitoring is adjusted according to the distance from the excavation face: 2 times / day when the distance from the excavation face is <1D (D is the tunnel diameter), 1 time / day when the distance is 1~2D, 1 time / (1~3) day when the distance is 2~5D, and 1-3 times / 7 days when the distance is >5D. During the operation period, only automated monitoring is adopted, and the frequency is uniformly 2 times / day.

[0013] The permanent pressure relief hole has a diameter of 50-80mm and a depth 100-200mm greater than the secondary lining thickness, ensuring that it extends to the water accumulation area behind the initial support after penetrating the secondary lining; the automatic control valve is an electromagnetic control valve, and its on / off state is automatically controlled by the data transmission and control module based on water pressure monitoring data.

[0014] A method for long-term monitoring and depressurization of water pressure behind tunnel lining during operation, using the system described in any one of claims 1-9, includes the following steps: S1: During the tunnel construction phase, at the cross-section of the high-pressure and water-rich section, a piezometer and a structural stress-strain sensor are pre-embedded between the initial support and the secondary lining. Permanent pressure relief holes are drilled at the bottom of the cable trenches on both sides of the tunnel and openable and closable devices are installed. S2: During the tunnel operation period, water pressure data and structural stress and strain data are collected twice a day by an automated integrated testing system. The collected data is sent to the data management and analysis subsystem via the data remote transmission subsystem. S3: The data management and analysis subsystem processes the monitoring data, plots time-varying curves, and compares them with preset safety thresholds. If the water pressure exceeds the threshold or the structural stress is abnormal, an early warning is immediately triggered, and relevant parties such as the owner, designer, construction, and supervisor are notified via SMS. S4: After receiving the warning, if it is a manual pressure relief mode, the maintenance personnel will go to the corresponding section to open the protective cover of the pressure relief hole to drain the accumulated water; if it is an automatic pressure relief mode, the data transmission and control module will directly control the automatic control valve to open and automatically drain the water. S5: During the depressurization process, continuously monitor water pressure changes. When the water pressure drops below the safety threshold, close the pressure relief hole and the opening / closing device. At the same time, regularly compile monitoring data and submit weekly or monthly reports to relevant parties. After the project is completed, submit a complete monitoring summary report and electronic documents to establish a tunnel health record.

[0015] The beneficial effects of this invention are: This invention organically combines long-term automated monitoring by the monitoring subsystem with proactive handling by the pressure relief subsystem, constructing a closed-loop system of "monitoring-early warning-pressure relief-feedback" to achieve full life-cycle management of water pressure risks behind the tunnel lining during operation. The system adopts a safety design of "multi-dimensional monitoring + dual-mode pressure relief." The monitoring subsystem integrates multiple types of sensors, such as piezometers, embedded strain gauges, and rebar gauges, covering key stress-bearing parts such as the lining arch crown, arch waist, arch foot, and invert arch, ensuring the comprehensiveness and accuracy of water pressure and structural stress data collection. The pressure relief subsystem, with a layout of permanent pressure relief holes in the entire longitudinal direction at 5-10m intervals, is equipped with a dual-mode opening and closing device of manual protective covers and automatic control valves, which can be flexibly adapted according to the risk level—precise manual handling in normal risk scenarios and automatic pressure relief within 10 seconds in high-risk scenarios, significantly shortening the overpressure handling time and significantly improving the tunnel operation safety assurance capability. Meanwhile, the data transmission and control module supports redundant backup of multiple communication methods (RS485, fiber optic, GPRS) to ensure the stability of data transmission in complex tunnel environments and avoid early warning failures. The system components are selected from mature and compatible industrial-grade products (such as vibrating wire sensors and waterproof solenoid valves), with a simple structural design and controllable procurement and initial installation costs. During operation, the automated integrated testing system enables unattended monitoring, eliminating the need for frequent manual inspections and significantly reducing maintenance labor costs. More importantly, by proactively depressurizing to mitigate water pressure risks in advance, the high repair and reinforcement costs (such as crack grouting and lining replacement) caused by the expansion of lining defects can be avoided. At the same time, tunnel downtime losses due to structural defects are reduced, achieving the goal of "small investment for great safety" with low cost and high efficiency. Furthermore, the long-term accumulated monitoring data can guide preventative maintenance, avoid over-repair, and further optimize the total life cycle cost. The system can be flexibly configured according to the tunnel's risk level and geological conditions (such as karst anomaly zones and high-pressure water-rich sections). Conventional high-risk tunnels adopt the "manual pressure relief + basic monitoring" mode, while high-risk tunnels are upgraded to the "automatic pressure relief + extended monitoring (cracks, surface stress)" mode, adapting to different engineering needs. The monitoring frequency can be dynamically adjusted according to the construction and operation periods. The sensors have reserved expansion interfaces, and surface crack gauges and string-type surface strain gauges can be quickly installed when lining defects are discovered later, without large-scale system modifications. It is compatible with subsequent operation and maintenance upgrades and is suitable for tunnels in operation under complex geological conditions such as various karst structures and high-pressure water-rich areas. The system not only realizes real-time acquisition and early warning of monitoring data, but also uses the regression analysis and time-varying curve plotting functions of the data management and analysis subsystem to explore the changing patterns of water pressure and structural stress, predict risk development trends, and provide quantitative basis for maintenance decisions (such as determining the timing of pressure relief and adjusting the spacing of pressure relief holes).Long-term accumulated tunnel health record data can feed back into the design optimization of similar tunnels (such as grouting thickness, monitoring section layout, and pressure relief hole parameter settings), forming a closed loop of technical iteration of "practice-data-optimization," and promoting the standardization and refinement of tunnel engineering safety monitoring technology; the automated integrated testing system is developed based on the general Windows platform, with a simple and intuitive interface, and operators can master it after short-term training; early warning information is pushed to relevant parties in real time via SMS, without the need for dedicated personnel to be on duty 24 hours a day; the pressure relief device (manual protective cover / automatic control valve) has a reliable structure and is easy to maintain, and the automatic control valve can be remotely controlled through the system, which greatly reduces the difficulty of on-site operation and maintenance, and is especially suitable for the complex working environment of tunnel sites. Attached Figure Description

[0016] The present invention will now be described in further detail with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the monitoring principle in this invention.

[0018] Figure 2 This is a schematic diagram of the monitoring principle in this invention.

[0019] Figure 3 This is a schematic diagram of the concrete stress measurement installation in this invention.

[0020] Figure 4 This is a diagram showing the arrangement of stress measurement points on the steel frame in this invention.

[0021] Figure 5 This is a schematic diagram of the automated integrated testing system architecture in this invention.

[0022] Figure 6 This is a diagram showing the arrangement of the piezometer measuring points in this invention. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0025] In the description of this invention, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. It should be noted that the terms "comprising," "including," or any other variations are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0026] like Figures 1-6 Example 1 shown (conventional risk tunnel application): This embodiment is applied to the monitoring of the Dejiang Tunnel during its operation. The tunnel site is located in the northeastern part of the Guizhou Plateau, in a low-mountainous landform of karst-tectonic type. The section from YK9+938 to YK9+998 is a special karst anomaly zone, where groundwater is prone to seep down along bedrock joints and fissures. The water pressure may exceed 3MPa, so it is necessary to focus on preventing and controlling the water pressure risk behind the lining.

[0027] System Configuration: Monitoring Subsystem: ZK9+938, ZK9+968, and ZK9+998 were selected as monitoring sections. Each section was equipped with 9 piezometers (for seepage pressure monitoring), 14 embedded strain gauges (7 locations × 2 measuring points for initial support concrete stress, 7 locations × 2 measuring points for secondary lining concrete stress), and 14 rebar gauges (7 locations × 2 measuring points for steel frame stress, 7 locations × 2 measuring points for secondary lining rebar stress), for a total of 65 measuring points per section. Piezometers were installed by drilling. Rebar gauges were wrapped with damp burlap to cool them down during welding. The initial frequency of the embedded strain gauges was tested after installation.

[0028] Table 1 below shows the number of monitoring points arranged along the monitoring section:

[0029] Table 1 Table 2 below shows the layout of monitoring points along the monitoring section:

[0030] Table 2 Pressure relief subsystem: Permanent pressure relief holes are laid longitudinally at the bottom of the cable trenches on both sides of the tunnel, with a hole spacing of 8m, a hole diameter of 60mm, and a hole depth that penetrates the secondary lining (thickness 500mm) and extends 150mm to the back of the primary support; the hole openings are equipped with manually operated protective covers made of stainless steel to prevent corrosion.

[0031] Data transmission and control module: Configured with 6 sets of 32-channel automated integrated testing systems (2 sets per section), data is transmitted remotely via GPRS (mobile signal coverage is good inside the tunnel), and the data management and analysis subsystem presets water pressure warning thresholds (cumulative value threshold 0.8MPa, daily change rate threshold 0.1MPa / d).

[0032] Operation process: Monitoring phase: During the operation period, data is automatically collected at 9:00 and 18:00 every day. The data is transmitted to the management center via GPRS, and the system automatically plots the water pressure time curve and the structural stress change curve.

[0033] Table 3 below shows the monitoring frequency:

[0034] Table 3 Early warning and response: During a monitoring session, the water pressure at the arched section of section ZK9+968 reached 0.85 MPa, exceeding the cumulative threshold. The system immediately triggered an early warning and notified relevant parties via SMS. Maintenance personnel arrived on site within 2 hours, opened the protective covers of the three pressure relief holes near the section, and continuously drained water for 4 hours until the water pressure dropped to 0.6 MPa. The protective covers were then closed.

[0035] Data feedback: Weekly monitoring data is compiled into a report, including the average water pressure at each section, the maximum structural stress, early warning records and handling status, and submitted to the owner and supervision unit; after one year of operation, a complete monitoring summary report and electronic health record are submitted.

[0036] Example 2 (High-risk tunnel application): This embodiment is an optimization based on Embodiment 1, and is applied to tunnels with larger water inflow and higher risk levels (such as the high-pressure, water-rich section of the Yuanliangshan Tunnel on the Chongqing-Huaihua Second Line), with a focus on improving the system's automation level and risk response speed.

[0037] System optimization configuration: Pressure relief subsystem: The manual protective cover of the pressure relief port is upgraded to an electromagnetic automatic control valve. The selected model is a DN50 waterproof electromagnetic valve, which is linked with the automated integrated testing system and can receive system switch commands.

[0038] Monitoring subsystem: New surface crack gauges and string surface strain gauges have been added. Sensor interfaces have been reserved at the arch waist and arch foot parts of the lining that are prone to cracking. Once a crack is detected, the equipment can be quickly installed and connected to the system to monitor the development of the crack in real time.

[0039] Data transmission and control module: The data acquisition frequency adjustment function is optimized. When the monitoring data shows abnormal fluctuations (such as a change of more than 0.05MPa from the previous acquisition), the system automatically increases the acquisition frequency to once per hour to accurately capture the water pressure change trend. At the same time, a large screen monitoring interface is added to the management center to display the monitoring data and early warning status of each section in real time.

[0040] Operational advantages: Automatic pressure relief: When the water pressure at section ZK9+998 reached 0.9MPa, the system triggered an early warning and sent an opening command to the three automatic control valves at the corresponding section. The valves responded and opened within 10 seconds without the need for manual intervention. After 1.5 hours, the water pressure dropped to 0.7MPa, and the system automatically closed the valves, significantly shortening the response time.

[0041] Crack monitoring: During the later stages of operation, a minor crack was found on the side wall of section ZK9+938. A surface crack gauge was installed through the reserved interface. The monitoring showed that the crack width was stable within 0.1mm. Combined with water pressure data, it was determined that there was no risk and excessive maintenance was avoided. If the crack width increases, the pressure relief system can be activated in time to adjust the water pressure and prevent the crack from expanding.

[0042] Example 1 is designed for conventional high-pressure water-rich tunnels (such as the karst anomaly zone of Dejiang Tunnel), with the core positioning of "reliable protection + economic practicality", and is suitable for tunnel scenarios with medium risk level and relatively stable water inflow during operation.

[0043] Core configuration and operating features 1. System Configuration: The system adopts a combination of "basic monitoring subsystem + manual pressure relief subsystem + standard data transmission module". The monitoring sections focus on key mileages ZK9+938, ZK9+968, and ZK9+998. Comprehensive monitoring of water pressure and structural stress is achieved through piezometers, embedded strain gauges, and rebar gauges. Pressure relief holes are arranged at 8m intervals and equipped with manual opening and closing protective covers. Data transmission adopts GPRS and presets fixed early warning thresholds to meet routine monitoring needs.

[0044] 2. Operational Results: The system effectively manages water pressure risks through a combination of automated data collection twice daily and manual handling of overpressure issues. For example, after an overpressure warning was issued at section ZK9+968, maintenance personnel promptly arrived at the site to open the pressure relief hole, and the water pressure was reduced within 4 hours, preventing any damage to the lining structure. Weekly data feedback forms standardized records, providing a clear basis for routine maintenance, ensuring both safety and controlling operation and maintenance costs.

[0045] It is suitable for conventional high-pressure water-rich tunnels with relatively clear geological conditions, moderate water inflow pressure (e.g., ≤3MPa), and moderate requirements for timely response. Its value lies in achieving a closed loop of "monitoring-early warning-response" with low-cost configuration, avoiding resource waste caused by over-design, and lowering the on-site operation and maintenance threshold through standardized operation, adapting to the safety needs of small and medium-sized tunnel projects.

[0046] Example 2 is an upgraded version based on Example 1, with the core positioning of "efficient response + precise control", which is suitable for tunnel scenarios with large water inflow, high risk level and strict requirements for timeliness of handling (such as the high-pressure water-rich section of Yuanliangshan Tunnel on the Chongqing-Huaihua Second Line).

[0047] 1. System Optimization Configuration: Three core upgrades have been added to the basic configuration: First, the pressure relief subsystem has been upgraded to an electromagnetic automatic control valve to achieve linkage control with the monitoring system; second, the monitoring subsystem has been expanded with interfaces for surface crack gauges and string surface strain gauges to support dynamic crack monitoring; third, the data transmission and control module has been optimized to "dynamic acquisition frequency + real-time monitoring on a large screen", which automatically increases the acquisition frequency to 1 time / hour in case of anomalies, accurately capturing changes in risk.

[0048] 2. Operational Advantages: Automation upgrades significantly improve risk response efficiency. In case of overpressure, the pressure relief valve automatically opens within 10 seconds, and water pressure can be reduced within 1.5 hours, requiring no manual intervention and significantly shortening the response cycle. The newly added crack monitoring function enables collaborative analysis of water pressure and cracks, preventing the expansion of hidden risks. For example, in monitoring cracks in the sidewall of section ZK9+938, the risk level is determined by combining water pressure data, avoiding excessive repairs and achieving precise prevention and control.

[0049] It is suitable for high-risk tunnels with complex geology, high water pressure (e.g., >3MPa), large fluctuations in water flow, and high requirements for safety redundancy. Its value lies in improving the system's response speed and control accuracy through "automated handling + extended monitoring," minimizing the risk of structural instability caused by high water pressure; at the same time, through dynamic data acquisition and reserved interface design, it adapts to risk changes during long-term operation, providing "proactive prevention + precise decision-making" support for the safety of high-grade tunnels throughout their entire life cycle.

[0050] The scope of protection of this invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this invention shall fall within the scope of protection of this invention.

Claims

1. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining, characterized by: The monitoring subsystem is used for continuously monitoring water pressure behind the tunnel lining and stress and strain state of the supporting structure; the pressure relief subsystem is used for actively draining accumulated water to control water pressure when water pressure behind the lining exceeds a safety threshold; the data transmission and control module is used for receiving monitoring data of the monitoring subsystem, triggering early warning after analysis and processing, and linking the pressure relief subsystem to perform pressure relief operation; the monitoring subsystem comprises a plurality of monitoring sections arranged along the longitudinal direction of the tunnel at intervals, a piezometer is pre-buried between the primary support and the secondary lining at each monitoring section, and each monitoring section is further provided with a sensor assembly for monitoring structural stress and strain.

2. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 1, characterized in that: The monitoring sections are selected at key milestones of a high-pressure water-rich section of the tunnel, the total number of measuring points at each monitoring section is 65, and key stress areas of the lining are covered.

3. The long-term monitoring and pressure-relief system for water pressure behind operational-tunnel lining according to claim 1, characterized in that: The sensor assembly comprises a buried strain gauge and a steel bar gauge; the buried strain gauge is used for monitoring primary support concrete stress and secondary lining concrete stress; the steel bar gauge is used for monitoring steel frame stress and secondary lining steel stress; two measuring points are arranged at each of the following seven positions of each monitoring section: arch crown, left and right haunches, left and right springers, and left and right side walls; one measuring point is arranged at each of the following nine positions of each section: arch crown, left and right haunches, left and right springers, left and right side walls, left inverted arch, and right inverted arch.

4. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 1, characterized in that: The pressure relief subsystem comprises permanent pressure relief holes arranged along the longitudinal direction of the tunnel; the permanent pressure relief holes penetrate through the secondary lining to the back of the primary support, the hole spacing is 5-10 m, and the actual water seepage of the tunnel can be dynamically adjusted; the hole of the permanent pressure relief hole is provided with an openable and closable device; the openable and closable device is a manually operated protective cover or an automatic control valve linked with the data transmission and control module.

5. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 1, characterized in that: The data transmission and control module comprises an automatic comprehensive test system, which comprises a data automatic acquisition subsystem, a data remote transmission subsystem, and a data management and analysis subsystem; the data automatic acquisition subsystem can be connected with a vibrating string sensor, an inductive sensor, and a temperature sensor to realize unattended automatic acquisition; the data remote transmission subsystem supports at least one of the following communication modes: RS485 bus, optical fiber, wireless data transmission, or GPRS; the data management and analysis subsystem can draw time curve of monitoring data, perform regression analysis, and trigger early warning when data exceeds a threshold.

6. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 5, characterized in that: The technical parameters of the automatic comprehensive test system meet the following requirements: strain measurement range is ±1500με, steel stress measurement range is ±300MPa, pressure measurement range is 0-5000kN, applicable environmental temperature is -10°C to +50°C, and AC 220V / 50Hz power supply is used for power supply.

7. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 1, characterized in that: The monitoring subsystem can also be extended to access surface joint meters and string surface strain gauges; when cracks or abnormal surface stress occur in the secondary lining of the tunnel, the surface joint meter is used to monitor crack development, and the string surface strain gauge is used to monitor the surface stress state of the lining.

8. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 1, characterized in that: The monitoring frequency of the monitoring subsystem is set by stages: during the construction period, manual monitoring and automatic monitoring are combined, the frequency of manual monitoring is adjusted according to the distance from the excavation working face, when the distance is <1D (D is the diameter of the tunnel), 2 times / day, when the distance is 1-2D, 1 time / day, when the distance is 2-5D, 1 time / (1-3) days, and when the distance is >5D, 1-3 times / 7 days; during the operation period, only automatic monitoring is used, and the frequency is uniformly 2 times / day.

9. A long-term monitoring and pressure relief system for water pressure behind a tunnel operating period lining according to claim 4, characterized in that: The diameter of the permanent pressure relief hole is 50-80mm, and the hole depth is 100-200mm larger than the thickness of the secondary lining, ensuring that the water accumulation area behind the primary support is extended after penetrating the secondary lining; the automatic control valve is an electromagnetic control valve, and its on-off state is automatically controlled by the data transmission and control module according to the water pressure monitoring data.

10. A method of long-term monitoring and pressure relief of water pressure behind the lining during the operational period of a tunnel, characterized by: The method comprises the following steps: S1: during the tunnel construction stage, a piezometer and a structural stress and strain sensor are pre-buried between the primary support and the secondary lining at the section of the high-pressure water-rich section, a permanent pressure relief hole is drilled at the bottom of the cable trough on both sides of the tunnel, and an openable and closable device is installed; S2: during the tunnel operation period, the automatic comprehensive test system collects water pressure data and structural stress and strain data at a frequency of 2 times / day, and the collected data is sent to the data management and analysis subsystem by the data remote transmission subsystem; S3: the data management and analysis subsystem processes the monitoring data, draws a time curve and compares it with a preset safety threshold, if the water pressure exceeds the threshold or the structural stress is abnormal, an early warning is triggered immediately, and the relevant parties such as the owner, the designer, the constructor, the supervisor, etc. are notified in the form of a short message; S4: after receiving the early warning, if it is a manual pressure relief mode, the maintenance personnel go to the corresponding section to open the pressure relief hole cover to drain the accumulated water, if it is an automatic pressure relief mode, the data transmission and control module directly controls the automatic control valve to open for automatic drainage; S5: the water pressure change is continuously monitored during the pressure relief process, when the water pressure drops below the safety threshold, the openable and closable device of the pressure relief hole is closed; at the same time, the monitoring data is regularly sorted out to form a weekly report or a monthly report to be submitted to the relevant parties, and a complete monitoring summary report and electronic document are submitted after the project is completed, and a tunnel health record is established.

Images