Composite wall leakage monitoring device and construction monitoring method

Abstract

The invention provides a composite wall leakage monitoring device and a construction monitoring method.The composite wall leakage monitoring device comprises a composite wall of an underground vertical barrier structure, the composite wall is composed of a geomembrane and backfill bentonite, and the composite wall leakage monitoring device is characterized in that a monitoring device is pre-buried in a weak area on the downstream side of the composite wall; the monitoring device comprises a time domain reflectometer TDR for monitoring the water content, a soil pressure meter for monitoring the total pressure of a soil body and a tensiometer for monitoring the pore water pressure; the provided monitoring instrument arrangement scheme has high pertinence and operability, and the monitoring instrument arrangement scheme and principle are further standardized; according to the burying method of the monitoring instrument, the advantages of materials are well utilized, the accuracy of the monitoring instrument at the fixed position of the underground hidden engineering is guaranteed, the survival rate of the monitoring instrument is greatly improved, the problems that the burying process of the monitoring instrument is complex and construction organization is difficult are solved, and the construction efficiency is improved. The system has the advantages of high monitoring range pertinence, simple and convenient burying construction and less cross construction interference.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering, specifically to a composite wall leakage monitoring device and construction monitoring method. Background Technology

[0002] Statistics show that there are currently over 1,500 operational municipal and industrial solid waste landfills in urban areas across China. For these older landfills, the traditional method of horizontally laying impermeable geomembranes at the bottom of the site to control the spread and escape of pollutants has been largely ineffective. However, due to the early development of geomembrane products in the last century and their long service life, the horizontal impermeable systems at the bottom of these landfills often fail, frequently resulting in leakage and subsequent pollutant escape, causing serious environmental pollution and significant social impact. Therefore, the remediation and treatment of older landfills in China is urgent, and the repair of impermeable systems has become a key technology in the remediation of these landfills.

[0003] The existing technology "CN118607050A" describes a survey and design method for a vertical barrier system for contaminated sites. This method involves setting up an effective vertical barrier system around the site to isolate pollutants from the surrounding environment, thereby effectively blocking the migration and diffusion of pollutants and reducing or eliminating the risks posed by site pollutants to human health and the environment. Therefore, vertical barrier technology has become a focus of research in site pollution control both domestically and internationally. Vertical barrier technologies mainly include curtain grouting, composite walls, and cement-mixed pile continuous walls. For sites with a contamination depth not exceeding 40m, composite walls are primarily used for the cover layer, while curtain grouting is mainly used for the bedrock. When the contamination depth exceeds 40m, a combination of upper walls and lower curtain grouting is employed.

[0004] In recent years, with the development of geomembrane materials, HPDE and TPO geomembranes have been widely used in ecological restoration projects (contaminated site remediation) due to their excellent impermeability, durability, strong corrosion resistance in complex polluted environments, low material cost, and good engineering economics. Combined with backfill bentonite, they form a geomembrane-bentonite composite wall, a vertical barrier structure. While curtain grouting and cement mixing pile continuous walls in vertical barriers can be tested using water pressure tests, the composite wall currently lacks effective testing or monitoring methods to evaluate its effectiveness due to the difficulty of installing monitoring sensors. However, composite walls are often located in critical areas for preventing seepage (pollution) diffusion, typically reaching depths of up to 30m. The geomembrane material in composite walls is limited by width, has numerous joints, complex construction processes, and high construction quality requirements; therefore, its barrier effect and operational reliability are crucial for ecological restoration projects. Thus, there is an urgent need to address the relative scarcity of monitoring sensor placement schemes for composite walls and the difficulty of sensor installation, in order to obtain continuous data to evaluate the construction quality and long-term operational performance of the composite wall, thereby ensuring the effectiveness of the vertical barrier system. Summary of the Invention

[0005] The main objective of this invention is to provide a composite wall leakage monitoring device and construction monitoring method to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a composite wall including an underground vertical barrier structure, the composite wall being composed of a geomembrane and backfill bentonite, characterized in that: a monitoring device is pre-embedded in the weak area on the downstream side of the composite wall, the monitoring device including a time domain reflectometer (TDR) for monitoring water content, an earth pressure gauge for monitoring total soil pressure, and a tensiometer for monitoring pore water pressure. A first locking strip is fixed on the geomembrane at the installation position corresponding to the monitoring device. The monitoring device is integrated and installed on multiple long strips of geomembrane. A second locking strip is fixed on one side of the long strip of geomembrane. The second locking strip is snapped and fixed to the first locking strip. It is also equipped with a data acquisition device, a data collection terminal, and a remote monitoring center. The time domain reflectometer (TDR), earth pressure gauge, and tension gauge transmit monitoring data to the data collection terminal through the data acquisition device, and the data in the data collection terminal is monitored in real time by the remote monitoring center for remote management.

[0007] Preferably, the monitoring devices are arranged according to the depth of the composite wall and determined based on the lithology, permeability, and pollutant strata information, with the burial depth spacing gradually increasing along the vertical direction.

[0008] Preferably, multiple long strips of geomembrane are used to integrate and install multiple time domain reflectometers (TDRs), earth pressure gauges, and tension gauges; Multiple time domain reflectometers (TDRs) are fixed on a first fixed geomembrane, and the first fixed geomembrane is heat-fused and bonded to a long strip geomembrane at intervals. The earth pressure gauge is fixed to the second fixed geomembrane, and the second fixed geomembrane is heat-fused and bonded to the long strip geomembrane at intervals. The tension gauge is fixed on the third fixed geomembrane, which is then heat-fused to the long strip geomembrane at intervals.

[0009] Preferably, the time domain reflectometer (TDR) is vertically fixed on the first fixed geomembrane. Multiple first bolts are provided around the TDR. The first bolts are fixed to the first fixed geomembrane by nuts. The base of the TDR is tied to the first bolts by fiber ropes for positioning and fixed by pouring epoxy resin. The centerline of the time domain reflectometer (TDR) is aligned with the centerlines of the first fixed geomembrane and the long strip geomembrane, and multiple TDRs on the long strip geomembrane are located on the same vertical line.

[0010] Preferably, a second bolt is provided on the connecting seat around the earth pressure gauge, and the second bolt is fixed to the second geomembrane by a nut; The center of the pressure cell of the earth pressure gauge is aligned with the center line of the second fixed geomembrane, and multiple earth pressure gauges on the long geomembrane are on the same vertical line.

[0011] Preferably, the tension meter is vertically mounted on the third fixed geomembrane via a mounting base. The mounting base is fixed to the third fixed geomembrane around its perimeter by third bolts and nuts. The tension meter is inserted into the central hole at the top of the mounting base and fixed by adhesive. The centerline of the tension meter is aligned with the centerline of the third fixed geomembrane, and multiple tension meters on the long geomembrane are on the same vertical line.

[0012] Preferably, the cross-sections of the first locking strip and the second locking strip are E-shaped structures that interlock with each other, and the end faces of the first locking strip and the second locking strip are respectively bonded to the geomembrane and the long strip geomembrane by hot melt bonding.

[0013] Preferably, multiple wire harness clips are spaced apart on the long strip geomembrane. The two ends of the wire harness clips are bonded to the long strip geomembrane by heat fusion. The middle of the wire harness clips is raised, and the wire harnesses of each sensor pass through the wire harness clips.

[0014] Preferably, the distance between the center line of the sensor on each strip of geomembrane and the center line of the grouting pipe is not less than 0.8m, and the distance from the connection joint on the geomembrane is not less than 0.5m. The horizontal spacing Dx between each sensor satisfies: 1m≤Dx≤width / 4.

[0015] A method for using a composite wall leakage monitoring device, comprising the following steps: S1. Investigate the geological and water level geological conditions of the site surrounding the vertical barrier composite wall, clarify the layout range and structural type of the composite wall, and demonstrate the key parameters of the thickness and depth of the composite wall. S2. Based on the layout of the vertical barrier composite wall structure, design a monitoring sensor layout scheme for the key weak areas of seepage prevention. S3. According to the monitoring sensor layout plan, mark the positioning points on the composite wall geomembrane and mark the center line position of the first locking strip, and heat-melt bond the first locking strip to the geomembrane. S4. Cut a strip of geomembrane and a second locking strip of appropriate width and length, mark the positioning points on the strip of geomembrane, and heat-melt bond the second locking strip to the strip of geomembrane. S5. The first, second, and third fixed geomembranes with sensors are heat-fused and bonded to the corresponding long strip geomembranes according to the positioning marks, and the wire harness is fixed to the wire harness clip in a serpentine pattern. S6. Construct on-site data collection terminals and a remote monitoring center, and build the necessary components for data collection, including site, network, cables, terminals, and cloud platform. S7. Use mechanical equipment to lower the geomembrane of the composite wall; S8. Align the first locking strip on the long strip geomembrane with the second locking strip on the geomembrane, which has already been fixed with the sensor, and slowly push the long strip geomembrane down until it can no longer be pushed. At this time, the top of the long strip geomembrane should be basically consistent with the top surface of the composite wall. S9. Install backfill casting pipes on both sides of the geomembrane; S10. Pour backfill material for the composite wall to replace the mud in the composite wall trench. S11. Perform composite wall maintenance and preliminary readings of each sensor to ensure the reliability of sensor survival and the rationality of data collection.

[0016] This invention provides a composite wall leakage monitoring device and construction monitoring method, with the following beneficial effects: 1. This invention is intended to supplement the current situation in underground concealed engineering projects in the fields of ecological governance and restoration projects / water conservancy and hydropower engineering construction, where there is a relative lack of monitoring schemes for vertical barrier composite anti-seepage walls and relatively inconsistent and unclear layout principles. It aims to promote the development of the underground vertical barrier composite wall industry and its engineering application prospects.

[0017] 2. This invention addresses the problems of complex installation processes, difficult construction organization, and uncontrollable instrument placement and monitoring specificity in underground concealed engineering projects such as ecological restoration and water conservancy and hydropower projects. It aims to obtain continuous and reliable monitoring data, reasonably evaluate the construction quality and long-term performance of the composite wall, and thus ensure the effectiveness of the vertical barrier system.

[0018] 3. The hot-melt welding of this invention occurs before the geomembrane is laid down for construction, which reduces the uncertainty of underground hidden works construction in the field of ecological governance and restoration projects / water conservancy and hydropower projects to a certain extent. At the same time, it innovatively utilizes the geomembrane and locking properties to reserve a certain width between the instrument fixing end and the geomembrane, so as to avoid the composite wall geomembrane being damaged when the monitoring instrument is laid down, and also improves the survival rate of the instrument.

[0019] 4. This invention provides recommended burial depths and locations for monitoring instruments, which can be further refined based on the depth of the composite wall, the location of contaminants, and actual geological information. Furthermore, the burial method proposed in this application allows for targeted deployment of monitoring instruments based on the aforementioned information, thereby collecting leakage data at different layers. This facilitates the subsequent establishment of an information management platform and the implementation of defect handling for the vertical barrier system.

[0020] 5. The monitoring instruments used in this invention are time domain reflectometers (TDR), earth pressure gauges, and tension gauges. However, the proposed installation methods and ideas are also applicable to other commonly used monitoring instruments such as conductivity meters and water pressure gauges. The geomembrane fixing and connection methods for installing monitoring instruments can also be developed and applied to other underground concealed projects. This is conducive to the development of composite wall technology in the fields of ecological governance projects / water conservancy and hydropower engineering construction, and provides a solid foundation for industry standards. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a three-dimensional schematic diagram of the composite wall layout range of the present invention; Figure 2 This is the present invention. Figure 1 Top-down view of monitoring local weak areas in the middle; Figure 3 This is a top view of a single strip of geomembrane connected to another geomembrane according to the present invention; Figure 4 This is the present invention. Figure 2 Front view of the layout of monitoring devices for vulnerable areas; Figure 5 This is a flowchart of the monitoring system connection process of the present invention; Figure 6 This is a top view of the installation of the time domain reflectometer (TDR) of this invention; Figure 7 This is the present invention. Figure 6 The front view; Figure 8 This is a top view of the earth pressure gauge of the present invention being installed; Figure 9 This is the present invention. Figure 8 Front view Figure 10 This is a top view of the tension gauge installation of the present invention; Figure 11 This is the present invention. Figure 10 The front view; In the diagram: Composite wall 1; Geomembrane 101; Bentonite 102; Monitoring device 2; Time Domain Reflectometer (TDR) 201; Earth Pressure Gauge 202; Tensioner 203; First fixed geomembrane 204; Second fixed geomembrane 205; Third fixed geomembrane 206; First bolt 207; Fiber rope 208; Second bolt 209; Mounting base 210; Third bolt 211; Long strip geomembrane 3; Wiring harness clip 301; First locking strip 4; Second locking strip 5; Data acquisition device 6; Data collection terminal 7; Remote monitoring center 8; Grouting pipe 9; Weak area 10. Detailed Implementation

[0022] Example 1 like Figures 1-11As shown, a composite wall leakage monitoring device includes a composite wall 1 with an underground vertical barrier structure. The composite wall 1 is composed of a geomembrane 101 and backfill bentonite 102. The device is characterized in that a monitoring device 2 is pre-embedded in the weak area on the downstream side of the composite wall 1. The monitoring device 2 includes a time domain reflectometer 201 for monitoring water content, an earth pressure gauge 202 for monitoring total soil pressure, and a tension gauge 203 for monitoring pore water pressure. A first locking strip 4 is fixed on the geomembrane 101 at the installation position corresponding to the monitoring device 2. The monitoring device 2 is integrated and installed on multiple long strip geomembranes 3. A second locking strip 5 is fixed on one side of the long strip geomembrane 3. The second locking strip 5 is snapped and fixed to the first locking strip 4. It is also equipped with a data acquisition device 6, a data collection terminal 7 and a remote monitoring center 8. The time domain reflectometer TDR201, earth pressure gauge 202 and tension gauge 203 transmit monitoring data to the data collection terminal 7 through the data acquisition device 6, and the data in the data collection terminal 7 is monitored in real time by the remote monitoring center 8 for remote management.

[0023] Composite wall 1 is a geomembrane-bentonite composite wall, commonly used for seepage prevention in hydropower projects or vertical barrier systems for contaminated sites. The formula for calculating the thickness of composite wall 1 is as follows: L=F S ×A×H B In the formula: L is the thickness of the vertical barrier; F S H represents the safety factor; H is the head difference between the two sides of the vertical seepage barrier; A and B are coefficients.

[0024] To facilitate the construction of composite wall 1 and the installation of monitoring devices, the minimum thickness of composite wall 1 shall not be less than 60cm.

[0025] Composite wall 1 is composed of geomembrane 101 and bentonite 102. Common types of geomembrane 101 include HDPE geomembrane and TPO geomembrane, with a thickness of 2.0~3.0mm. Common types of bentonite 102 include soil-bentonite and cement-bentonite. When the site is saturated with water for a long time, i.e., the groundwater seepage line is high, soil-bentonite backfilling is preferred; otherwise, cement-bentonite backfilling is recommended.

[0026] The monitoring device 2 is arranged in conjunction with the composite wall 1 at varying depths. The depth is determined based on information such as stratum lithology, stratum permeability, and pollutant location. The spacing between sensors gradually increases along the vertical direction, with a maximum of four layers. The recommended burial depths between each sensor and the top of the composite wall 1 are shown in Table 1. The monitoring device 2 transmits data to the data acquisition device 6 via wires. To avoid interference from other sensors on the wiring, the wires are routed in a serpentine pattern along the long strip of geomembrane 3 and secured using tape, webbing, or wire harness clips 301.

[0027] Table 1 Recommended Layout of Composite Wall Monitoring Instrument Burial Depth

[0028] When the monitoring device 2 is arranged, the distance between the center line of the sensor and the center line of the grouting pipe 9 shall not be less than 0.8m, and the distance from the connection joint on the geomembrane 101 shall not be less than 0.5m. At the same time, the horizontal spacing D between each sensor shall be... x satisfy: 1m≤D x ≤width / 4 The monitoring device type 2 includes a time domain reflectometer (TDR) 201 for monitoring water content, an earth pressure gauge 202 for monitoring total soil pressure, and a tensiometer 203 for monitoring pore water pressure. Compared to the earth pressure gauge 202 and the tensiometer 203, the time domain reflectometer (TDR) 201 for monitoring water content should be closer to the centerline of the grouting pipe 9.

[0029] Data acquisition device 6 consists of a TDR200 terminal, a multi-channel vibrating wire / voltage signal data acquisition instrument, and a multi-channel digital signal acquisition instrument; data collection terminal 7 consists of a desktop computer and a cloud platform. Remote monitoring center 8 can monitor data from the on-site desktop computer and cloud platform in real time, and set thresholds for each monitoring parameter based on the on-site test results, providing threshold alarm functions to meet the needs of regulatory personnel for remote management and maintenance personnel for remote display.

[0030] The time domain reflectometer TDR201 is a three-needle type, which is electrically connected to the TDR200 terminal, and the TDR200 terminal is connected to the desktop computer on site.

[0031] The Earth Pressure Gauge 202 is a vibrating wire type, with single-sided force application. Its specifications are selected according to the earth pressure testing range. It is electrically connected to a multi-channel vibrating wire / voltage signal data acquisition instrument, and then connected to a cloud platform.

[0032] The 203 tension meter is selected based on the pore water pressure testing range. It is electrically connected to a multi-channel digital signal acquisition instrument, which is then connected to a cloud platform.

[0033] The first fixed geomembrane 204, the second fixed geomembrane 205, and the third fixed geomembrane 206 are used to install and fix sensors. They are 1.5~2.5mm thick, and their cross-sectional shape is determined by the fixed sensor. The geomembrane dimensions vary. The first fixed geomembrane 204 used for the time domain reflectometer TDR201 has a width ≥25 cm and a length ≥25 cm; The second fixed geomembrane 205 used for earth pressure gauge 202 has a width ≥30 cm and a length ≥70 cm; The third fixed geomembrane 206 used for tension meter 203 has a width ≥ 20 cm and a length ≥ 20 cm.

[0034] The time domain reflectometer TDR201 is vertically fixed on the first fixed geomembrane 204. Multiple first bolts 207 are provided around the time domain reflectometer TDR201. The first bolts 207 are fixed to the first fixed geomembrane 204 by nuts. The base of the time domain reflectometer TDR201 is tied and positioned to the first bolts 207 by fiber ropes 208 and fixed by pouring epoxy resin. The centerline of the time domain reflectometer (TDR201) is aligned with the centerlines of the first fixed geomembrane 204 and the long strip geomembrane 3, and multiple time domain reflectometers (TDR201) on the long strip geomembrane 3 are located on the same vertical line.

[0035] The earth pressure gauge 202 is equipped with a second bolt 209 on the connecting seat around it. The second bolt 209 is fixed to the second fixed geomembrane 205 by a nut. The center of the pressure cell of the earth pressure gauge 202 is aligned with the center line of the second fixed geomembrane 205, and multiple earth pressure gauges 202 on the long geomembrane 3 are on the same vertical line.

[0036] The tension meter 203 is vertically mounted on the third fixed geomembrane 206 via the mounting base 210. The mounting base 210 is fixed to the third fixed geomembrane 206 around the perimeter by the third bolts 211 and nuts. The tension meter 203 is inserted into the center hole at the top of the mounting base 210 and fixed by adhesive. The centerline of the tension meter 203 is aligned with the centerline of the third fixed geomembrane 206, and multiple tension meters 203 on the long geomembrane 3 are on the same vertical line.

[0037] Example 2 Further explanation based on Example 1, engineering example: A certain landfill was a sanitary landfill designed and constructed according to regulations for the safe disposal of waste. It began operation in 2001 and has served for nearly 20 years. However, long-term operation beyond its capacity has led to significant environmental risks and safety hazards. Although the landfill is closed, it will continue to generate large amounts of leachate for a considerable period, posing a significant potential source of pollution. Therefore, vertical anti-seepage measures were adopted to ensure the relative independence of the hydrogeological units within the landfill area, effectively blocking leachate exposure pathways both inside and outside the landfill. This was supplemented by groundwater risk management through various methods, including groundwater level control, pumping and treatment, and long-term monitoring.

[0038] The site's northwest side has the lowest elevation and a low natural groundwater level, with the groundwater flowing from southeast to northwest. Therefore, the north and northwest sides of the site are the main directions of seepage-pollutant coupling and diffusion. Composite walls are installed to prevent leachate and contaminated groundwater from overflowing. Generally, whether for ecological remediation projects or hydropower projects, the composite wall should be inserted 2m into the top surface of the relative impermeable layer. Considering the stability of the trench wall and the economic efficiency of the project, the composite wall depth generally does not exceed 40m. In this example, the preferred depth is 20-35m. The thickness of the composite wall is determined by a calculation formula; in this example, it is preferably 0.8m.

[0039] Based on the key areas for pollution prevention, composite wall monitoring sensors were installed at two locations: the northwest side at the junction of the composite walls and the north side at the complex geological conditions of the curtain wall. A detailed explanation of the sensor placement is provided below. The composite wall depth in this area is approximately 26-30m, with 28m selected. In this example, composite wall 1 is preferably an HDPE geomembrane with a thickness of 3.0mm, and the backfill material is preferably cement-bentonite backfill.

[0040] Taking the monitoring sensors arranged on two membranes in the middle as an example, if the composite wall depth is <30m, the recommended burial depth for the monitoring sensors is 5±1m, 10m±3m, and 20±5m. Based on information such as the lithology, permeability, and contaminant layer of the landfill site, the preferred burial depth for the monitoring sensors in this example is 6m, 12m, and 21m.

[0041] When arranging monitoring device 2, the distance between the centerline of the sensor and the centerline of the grouting pipe 9 should be no less than 0.8m, and the distance from the connection joint of the composite wall 1 should be no less than 0.5m. Simultaneously, the horizontal spacing Dx between each sensor should satisfy 1m ≤ Dx ≤ width / 4. In this example, the width of the composite wall geomembrane 101 is preferably 6m, i.e., Dx satisfies 1.0m ≤ Dx ≤ 1.5m. Considering the rationality of the arrangement, the distance between the centerline of the sensor and the centerline of the grouting pipe 9 is preferably 1.0m, the spacing between different sensors is 1.0m, and the distance from the membrane connection joint is 1.0m.

[0042] Given the large size of the landfill, the high volume of leachate leaching, and the stringent pollution prevention requirements in this example, a time-domain reflectometry (TDR) 201, an earth pressure gauge 202, and a tensiometer 203 were simultaneously deployed as monitoring sensors. The TDR 201 was symmetrically arranged around the centerline of the grouting pipe 9 to monitor changes in moisture content. The earth pressure gauge 202 and tensiometer 203 were positioned on either side of the membrane, spaced 1.0m apart, without distinguishing left from right; the display shows the left side. The earth pressure gauge 202 monitors changes in earth pressure and temperature, while the tensiometer 203 monitors changes in pore water pressure. All sensors were embedded on the downstream side of the composite wall.

[0043] The time domain reflectometer (TDR201) is connected to the TDR200 terminal via external wires as data acquisition device 6. In this example, there are many field sensors, so an SDM8X50 expansion was added to the TDR200 terminal to meet the data requirements. The TDR200 terminal is connected to a field desktop computer as a data collection terminal 7.

[0044] The earth pressure gauge 202 is connected to a multi-channel vibrating wire / voltage signal data acquisition instrument as a data acquisition device 6 after the external wire is connected. In this example, a 32-channel vibrating wire / voltage signal data acquisition instrument is preferred, and then connected to a 4G cloud platform as a data collection terminal 7.

[0045] The tension meter 203 is connected to a multi-channel digital signal acquisition instrument as a data acquisition device 6 after being connected to an external wire. In this example, a 6-channel digital signal acquisition instrument is preferred. It is then connected to a 4G cloud platform as a data collection terminal 7.

[0046] Each data collection terminal 7 is ultimately connected to the remote monitoring center 8. The remote monitoring center 8 can monitor data from on-site desktop computers and cloud platforms in real time, and set thresholds for each monitoring parameter based on the results of on-site tests, providing threshold alarm functions to meet the needs of regulatory personnel for remote management and maintenance personnel for remote display.

[0047] Example 3 To further illustrate with reference to Example 2, a method for using a composite wall leakage monitoring device is described below: The survey and design of the vertical barrier system involves identifying the geological and water level conditions of the site surrounding the vertical barrier composite wall, clarifying the layout and structural type of the composite wall, demonstrating key parameters such as the thickness and depth of the composite wall, and preparing a special design report on the composite wall.

[0048] Based on the structural layout of the vertical barrier composite wall, a special report on the design of composite wall monitoring was prepared, focusing on the selection and placement of monitoring sensors for key seepage (pollution) prevention areas.

[0049] The selection of sensors, their burial depth, and horizontal spacing are determined comprehensively based on information such as stratum lithology, stratum permeability, contaminant location, and composite wall layout. The layout scheme is briefly described below: Monitoring will be conducted on key areas on the north and northwest sides of the project. The selected sensors are a time domain reflectometer (TDR) for monitoring water content, an earth pressure gauge for monitoring total soil pressure, and a tension meter for monitoring pore water pressure.

[0050] The monitoring sensors are buried at progressively increasing depths along the vertical direction, with three layers of sensors arranged at burial depths of 6m, 6m, and 21m (wall depth < 30m, north side) or 3m, 8m, 15m, and 25m (wall depth > 30m, northwest side).

[0051] The distance between the center line of the sensor and the center line of the grouting pipe is 1.0m, the distance between the sensor and the membrane connection seam is 1.0m, and the horizontal distance between each sensor is 1.0m.

[0052] Vertical barrier construction preparation, construction platform and guide wall construction.

[0053] The construction of the underground vertical barrier composite wall involves trenching, and the trenching process employs a mud slurry wall stabilization technique.

[0054] According to the monitoring sensor installation plan, prefabricate small pieces of geomembrane and molds for fixing, and prepare fixing auxiliary materials such as bolts, fiber ropes, glass glue, nylon cable ties, and tape.

[0055] Mark the location of the monitoring sensor on a small piece of geomembrane.

[0056] According to the calibrated positions, the monitoring sensors are fixed one by one on a special small piece of geomembrane.

[0057] According to the monitoring sensor installation plan, positioning points are marked on the composite wall geomembrane, and the center line position of the locking buckle is marked.

[0058] According to the monitoring sensor installation plan, cut a strip of geomembrane and geomembrane buckle of appropriate width and length, and mark the positioning points on the strip of geomembrane.

[0059] The interlocking clips are paired in pairs; one is welded to the elongated geomembrane, and the other is welded to the composite wall geomembrane. The bottom of the interlocking clip welded to the composite wall geomembrane is heat-sealed.

[0060] Small pieces of geomembrane with monitoring sensors fixed to them are welded onto long strip geomembrane according to the positioning marks, and external wires are fixed onto long strip geomembrane in a serpentine pattern.

[0061] Construct on-site data collection terminals and a remote intelligent monitoring center, and build essential data collection components such as site, network, cables, terminals, and cloud platform.

[0062] Mechanical equipment is used to lower and weld the interlocking composite wall geomembrane.

[0063] Align the locking side of the long strip geomembrane with the monitoring sensor already fixed, with the locking side of the composite wall geomembrane, and slowly push the long strip geomembrane down until it can no longer be pushed. At this point, the top of the long strip geomembrane should be basically aligned with the top surface of the composite wall.

[0064] Backfill material pouring pipes are installed on both sides of the geomembrane.

[0065] The composite wall backfill material is poured to replace the mud in the composite wall trough.

[0066] The maintenance of the composite wall and the initial readings of various monitoring sensors are used to ensure the reliability of sensor survival and the rationality of data collection.

[0067] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A composite wall leakage monitoring device, comprising a composite wall (1) of underground vertical barrier structure, the composite wall (1) being composed of a geomembrane (101) and backfill bentonite (102), characterized in that: The monitoring device (2) is embedded in the weak area (10) on the downstream side of the composite wall (1), and the monitoring device (2) comprises a time domain reflectometer TDR (201) for monitoring water content, a soil pressure gauge (202) for monitoring total pressure of soil, and a tension gauge (203) for monitoring pore water pressure; A first lock strip (4) is fixed on the geomembrane (101) at a position corresponding to the installation position of the monitoring device (2), the monitoring device (2) is integratedly installed on a plurality of long strip geomembranes (3), one side of the long strip geomembrane (3) is fixed with a second lock strip (5), and the second lock strip (5) is clamped and fixed with the first lock strip (4). The data acquisition device (6), the data collection terminal (7) and the remote monitoring center (8) are further provided, the time domain reflectometer TDR (201), the soil pressure gauge (202) and the tension gauge (203) transmit monitoring data to the data collection terminal (7) through the data acquisition device (6), and the data in the data collection terminal (7) is monitored in real time through the remote monitoring center (8) for remote management.

2. The composite wall leakage monitoring device of claim 1, wherein: The monitoring device (2) is arranged according to the depth of the composite wall (1), and is determined according to the lithology of the stratum, the water permeability of the stratum and the information of the pollutant layer.

3. The composite wall leakage monitoring device of claim 1, wherein: The plurality of long strip geomembranes (3) are respectively used for integratedly installing the plurality of time domain reflectometers TDR (201), the soil pressure gauges (202) and the tension gauges (203); The plurality of time domain reflectometers TDR (201) are fixed on the first fixed geomembrane (204), and the first fixed geomembrane (204) is heat-fused and adhered on the long strip geomembrane (3) at intervals; The soil pressure gauges (202) are fixed on the second fixed geomembrane (205), and the second fixed geomembrane (205) is heat-fused and adhered on the long strip geomembrane (3) at intervals; The tension gauges (203) are fixed on the third fixed geomembrane (206), and the third fixed geomembrane (206) is heat-fused and adhered on the long strip geomembrane (3) at intervals.

4. The composite wall leakage monitoring device of claim 3, wherein: The time domain reflectometer TDR (201) is vertically fixed on the first fixed geomembrane (204), a plurality of first bolts (207) are arranged on the periphery of the time domain reflectometer TDR (201), the first bolts (207) are fixed with the first fixed geomembrane (204) through nuts, the base of the time domain reflectometer TDR (201) is positioned and fixed with the first bolts (207) through a fiber string (208), and epoxy resin is poured for fixing; The center line of the time domain reflectometer TDR (201) is consistent with the center lines of the first fixed geomembrane (204) and the long strip geomembrane (3), and the plurality of time domain reflectometers TDR (201) on the long strip geomembrane (3) are located on the same plumb line.

5. The composite wall leakage monitoring device of claim 3, wherein the soil is clay. Second bolts (209) are arranged on the connecting seats around the pressure gauges (202), and the second bolts (209) are fixed with the second fixed geomembrane (205) through nuts; The center of the pressure box of the soil pressure gauges (202) is consistent with the center line of the second fixed geomembrane (205), and the plurality of soil pressure gauges (202) on the long strip geomembrane (3) are located on the same plumb line.

6. The composite wall leakage monitoring device of claim 3, wherein the tensioning means is a cable. The tension meter (203) is vertically installed on the third fixed geomembrane (206) through the mounting seat (210), the mounting seat (210) is fixed around the third fixed geomembrane (206) through the third bolt (211) and the nut, the tension meter (203) is inserted into the center hole at the top of the mounting seat (210), and is fixed through glue adhesion; The center line of the tension meter (203) is consistent with the center line of the third fixed geomembrane (206), and the plurality of tension meters (203) on the long strip geomembrane (3) are on the same plumb line.

7. The composite wall leakage monitoring device of claim 1, wherein: The cross section of the first locking strip (4) and the second locking strip (5) is an E-shaped structure that is mutually clamped, and the end faces of the first locking strip (4) and the second locking strip (5) are respectively adhered on the geomembrane (101) and the long strip geomembrane (3) through hot melting.

8. The composite wall leakage monitoring device of claim 1, wherein: A plurality of wire harness clamps (301) are arranged on the long strip geomembrane (3) at intervals, the wire harness clamps (301) are adhered on the long strip geomembrane (3) through hot melting at both ends, the wire harness clamps (301) are protruded at the middle, and the wire harness of each sensor passes through the wire harness clamps (301).

9. The composite wall leakage monitoring device of claim 3, wherein: The distance between the center line of each sensor on the long strip geomembrane (3) and the center line of the grouting pipe is not less than 0.8 m, the distance from each sensor to the connecting seam on the geomembrane (101) is not less than 0.5 m, and the horizontal distance Dx between each sensor satisfies: 1m≤Dx≤width / 4.

10. The use method of the composite wall leakage monitoring device according to any one of claims 1-8, the method steps are as follows: S1, find out the geological conditions and water level geological conditions of the vertical barrier composite wall surrounding site, determine the composite wall arrangement range and structure type, and demonstrate the key parameters of the composite wall thickness and depth; S2, according to the structure arrangement of the vertical barrier composite wall, design the monitoring sensor arrangement scheme for the key weak area of the anti-seepage; S3, according to the monitoring sensor arrangement scheme, mark the positioning points on the geomembrane (101) of the composite wall, and mark the center line position of the first locking strip (4), and hot melt the first locking strip (4) on the geomembrane (101); S4, cut the long strip geomembrane (3) and the second locking strip (5) with appropriate width and length, and mark the positioning points on the long strip geomembrane (3), and hot melt the second locking strip (5) on the long strip geomembrane (3); S5, according to the positioning points, hot melt the first fixed geomembrane (204), the second fixed geomembrane (205) and the third fixed geomembrane (206) fixed with sensors on the corresponding long strip geomembrane (3), and fix the wire harness on the wire harness clamp (301) in a serpentine manner; S6, build the site data collection terminal (7) and the rear remote monitoring center (8), and build the necessary elements of site, network, cable, terminal and cloud platform data collection; S7, use mechanical equipment to lower the geomembrane (101) of the composite wall; S8, align the first locking strip (4) on the long strip geomembrane (3) with the second locking strip (5) on the geomembrane (101), and slowly push the long strip geomembrane (3) to continue to lower until it cannot be pushed further, at this time the top of the long strip geomembrane (3) should be basically consistent with the top surface of the composite wall (1). S9, backfilling pipe is arranged under the geomembrane (101) on both sides; S10, backfilling of the composite wall is poured, and the mud is replaced out of the composite wall groove; S11, maintenance of the composite wall and initial reading of each sensor are performed to ensure the reliability of survival of the sensor and the rationality of data acquisition.

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