Electrical resistivity tomography detection method and apparatus for leakage at joint of underground diaphragm wall

Abstract

An electrical resistivity tomography detection method for leakage at a joint of an underground diaphragm wall, comprising: S1, selecting a joint region to be detected; S2, drilling and arranging power supply electrodes; S3, arranging a plurality of detection points; S4, performing signal measurement; and S5, determining a leakage point. The present invention further relates to an electrical resistivity tomography detection apparatus for leakage at a joint of an underground diaphragm wall, comprising: an electrical measurement instrument (1), a transmitter (2) and a receiver (3) which are disposed above an underground diaphragm wall (10), wherein the transmitter (2) is electrically connected to a power supply electrode A (4) and a power supply electrode B (5), and the receiver (3) is electrically connected to a measurement electrode M (6) and a measurement electrode N (7). The technical problem in the prior art of detection limitations, especially the difficulty in identifying and locating leakage at the joint of the underground diaphragm wall is solved. By employing electrical resistivity tomography technology in combination with an electrode apparatus, comprehensive and accurate detection for the joint region of the underground diaphragm wall is realized, thereby effectively ensuring the construction quality and long-term safety of the underground diaphragm wall.

Description

Underground continuous wall joint leakage resistive tomography detection method and device TECHNICAL FIELD

[0001] The present application relates to the technical field of building engineering, and particularly relates to an underground continuous wall joint leakage resistive tomography detection method and device. BACKGROUND

[0002] High-rise buildings, subways, bridges and other projects often use underground continuous walls as foundation pit retaining structures to withstand lateral water and soil pressure. However, leakage often occurs at the joints of underground continuous walls, which seriously affects the quality and safety of the project. Underground continuous walls are structures used in complex environments, and their main function is to prevent erosion of groundwater and soil. However, due to the inevitable joints and material differences during construction, these joints often become weak links for leakage. If the leakage problem is not solved in a timely and effective manner, it will not only affect the structural safety of the building, but also may cause a series of environmental problems, such as foundation settlement, soil pollution, etc., further threatening the overall safety and stability of the project. The existing detection methods such as drilling core method and acoustic transmission method can detect the leakage problem of underground continuous walls to some extent, but they each have obvious limitations. The drilling core method requires drilling and sampling on the underground continuous wall to determine whether there is leakage by analyzing the situation of the sampling site. However, this method itself causes damage to the wall, and can only detect a limited number of sample points, and cannot fully reflect the situation of the entire wall. Each detection requires drilling operation, which is time-consuming and labor-intensive, and increases the cost of wall repair. Especially in some completed or operating projects, drilling operation is difficult, and there is a great practical operation difficulty. TECHNICAL PROBLEM

[0003] The acoustic transmission method is a non-destructive detection method that determines the density and uniformity of the underground continuous wall by sending and receiving acoustic waves to infer whether there is leakage. However, the acoustic transmission method is easily affected by the complex conditions of the underground environment in actual application, and the detection result is not stable and accurate. The acoustic wave is greatly affected by soil, groundwater and building materials during transmission, and is prone to errors, especially in the presence of a large number of heterogeneous materials or uneven structures, the reliability of the detection result is greatly discounted. In addition, the detection range of the acoustic transmission method is limited, and it is difficult to comprehensively and systematically detect the joints of the entire underground continuous wall. Therefore, a non-destructive and comprehensive leakage detection method is urgently needed to solve the above problems. TECHNICAL SOLUTION

[0004] In view of the above technical problems, the present disclosure provides a diaphragm wall joint leakage resistivity tomography detection method and device, which solves the limitations in the prior art, especially the technical problems of difficult detection and positioning of diaphragm wall joint leakage. The present application provides an efficient and non-destructive leakage detection method. By using resistivity imaging technology and combining with electrode devices, comprehensive and accurate detection of the diaphragm wall joint area is realized, thereby effectively ensuring the construction quality and long-term safety of the diaphragm wall.

[0005] According to one aspect of the present disclosure, a diaphragm wall joint leakage resistivity tomography detection method is provided, comprising the following steps:

[0006] S1, selecting the joint area to be detected: after the construction of the diaphragm wall is completed and before the excavation of the foundation pit, the joint area to be detected is selected and the foundation pit environment is evaluated;

[0007] S2, drilling and arranging power supply electrodes: drilling a hole at the center of the foundation pit, the depth of the hole being less than the depth of the foundation pit, arranging a power supply electrode A at the bottom of the hole, and arranging a power supply electrode B at a position at least one time the length of the foundation pit away from the center of the foundation pit;

[0008] S3, arranging a plurality of detection points: arranging a plurality of detection points around the foundation pit along the extension direction of the diaphragm wall on the ground, the distance between adjacent detection points being d p , and arranging a measurement electrode M and a measurement electrode N at each detection point in a direction perpendicular to the diaphragm wall, the distance between the measurement electrode M and the measurement electrode N being l MN , and respectively located on both sides of the diaphragm wall;

[0009] S4, signal measurement: connecting the power supply electrode A and the power supply electrode B to the transmitter of the electrical measuring instrument, connecting the measurement electrode M and the measurement electrode N to the receiver of the electrical measuring instrument, starting the electrical measuring instrument, supplying power to the diaphragm wall and the surrounding rock through the power supply electrode, and the measurement electrode receiving the potential difference signal and recording the data;

[0010] S5, judging the leakage point: processing the collected potential difference data to draw a resistivity distribution map of the diaphragm wall joint area, thereby judging the position and range of the leakage point.

[0011] In some embodiments of the present disclosure, the step of evaluating the foundation pit environment in step S1 comprises the following steps:

[0012] a. Review construction records: review the construction records of the diaphragm wall, the design, construction process and material usage of the joint, identify the joint area with problems,

[0013] b. Appearance inspection: Conduct a comprehensive inspection of the underground continuous wall for cracks and other appearance defects. Based on the results of the appearance inspection, preliminarily determine the joint areas that need to be focused on for testing;

[0014] c. Determine the testing joint areas: Analyze the stress conditions and potential leakage paths of the underground continuous wall in combination with the geological survey report and design drawings. Evaluate the risks of the joints based on the groundwater level, soil properties, and surrounding environmental factors to determine the final testing joint areas;

[0015] d. Clean the foundation pit environment: Before the foundation pit is excavated, evaluate the environmental conditions in the foundation pit, including the groundwater level, soil stability, and harmful gas factors. If there is accumulated water or soft soil in the foundation pit, first perform drainage and soil reinforcement to ensure the dryness and stability of the electrode arrangement area, and clean up the debris, garbage, and loose soil in the foundation pit to provide a flat working surface for the installation of the electrode device.

[0016] In some embodiments of the present disclosure, the drilling in step S2 includes the following steps:

[0017] Use a drilling machine to drill at the center position of the foundation pit. The bottom of the drill hole is not more than the measuring distance of the electrode from the bottom of the foundation pit to achieve electrode contact with the measuring layer. After drilling is completed, clean the debris and mud in the hole to keep the inside of the drill hole clean;

[0018] In some embodiments of the present disclosure, the step S2 of arranging the power supply electrode includes the following steps:

[0019] a. Install the power supply electrode A: Install the power supply electrode A into the drill hole with the help of electrode installation tools. Use conductive glue or filling material to reduce contact resistance to ensure that the electrode is in close contact with the drill hole wall. Use cement or other fixing materials to fix the electrode in the drill hole to prevent the electrode from being displaced due to external forces;

[0020] b. Install the power supply electrode B: According to the length of the foundation pit, calculate the position of the power supply electrode B at a position at least one time the length of the foundation pit. The position of the power supply electrode B and the power supply electrode A maintains a straight line relationship to ensure uniform distribution of the current field. Repeat the drilling operation and installation process at the determined position according to the previous steps to install the power supply electrode B;

[0021] c. Connect the electrical measuring instrument and check: Connect the power supply electrode A and the power supply electrode B to the transmitter of the electrical measuring instrument and perform a circuit flow check. After the electrode arrangement work is completed, perform a safety check to ensure that the electrodes and connection lines are safe and reliable to avoid posing a threat to construction personnel or equipment.

[0022] In some embodiments of the present disclosure, the step S3 of arranging a plurality of detection points comprises the following steps: according to the size of the foundation pit and the layout of the diaphragm wall, marking the position of each detection point on the ground, and using a drilling machine to drill a hole at the corresponding detection point position, so that the drilling depth reaches the expected measurement layer, then installing the measurement electrode M and the measurement electrode N into the hole respectively, using conductive glue or filling material to ensure that the electrodes are in close contact with the hole wall to reduce the contact resistance, and using cement or other fixing materials to fix the electrodes to prevent them from moving due to external force.

[0023] In some embodiments of the present disclosure, the step S4 of signal measurement comprises the following steps: starting the electrical measuring instrument, performing system self-checking to ensure that the instrument is working properly; supplying power to the diaphragm wall and the surrounding rock-soil mass through the power supply electrodes A and B to create a stable current field; the measurement electrodes M and N detect the potential difference signal caused by the current field, and the electrical measuring instrument records the measurement data in real time, including the potential difference value, the measurement time, and the environmental conditions; preliminarily analyzing the data to check its consistency and reliability, and finally transmitting the data to a computer for further processing and analysis using ERT imaging software to reconstruct the resistivity distribution image.

[0024] In some embodiments of the present disclosure, the step S5 of determining the leakage point comprises the following steps:

[0025] a. Data processing and resistivity calculation: first, check the consistency and integrity of the data to exclude obviously erroneous measurement data to ensure data quality; then remove outliers caused by external interference or instrument failure; subsequently, perform standardization processing on the data to eliminate the influence of systematic errors and background noise; during data processing, select a suitable inversion algorithm, including least squares method, conjugate gradient method or nonlinear inversion algorithm, to reconstruct the resistivity distribution from the potential difference data; apply the selected algorithm to process the data to calculate the resistivity of the diaphragm wall and the surrounding rock-soil mass;

[0026] b. Inversion and reconstruction of resistivity: import the processed data into the ERT special software and set the inversion parameters, including the position of the measurement electrodes, the electrode spacing and the geological structure; after running the software, reconstruct the resistivity distribution map according to the inversion results; perform smoothing processing or adjustment on the image to improve the readability and accuracy of the image;

[0027] c. Leakage evaluation and suggestion: identify the area of abnormal resistivity on the resistivity distribution map, determine the position of the leakage point according to the position and range of the abnormal resistivity, and analyze the shape and size of the abnormal area to evaluate the range and severity of the leakage; record the resistivity distribution map, the position and range of the leakage point in the report, and make appropriate repair or monitoring suggestions according to the analysis results.

[0028] According to another aspect of the present disclosure, a diaphragm wall joint leakage resistivity tomography device comprises an electrical measuring instrument arranged above the diaphragm wall, the electrical measuring instrument comprising a transmitter and a receiver, the transmitter being electrically connected to a power supply electrode A and a power supply electrode B, the power supply electrode A being located at the center of the foundation pit, and the power supply electrode B being located at a position at least one time the length of the foundation pit away from the center of the foundation pit; the receiver being electrically connected to a plurality of monitoring components arranged around the foundation pit along the extension direction of the diaphragm wall, the monitoring components comprising measuring electrodes M and N arranged on both sides of the diaphragm wall along the direction perpendicular to the diaphragm wall.

[0029] In some embodiments of the present disclosure, the power supply electrode A and the power supply electrode B are graphite electrodes, and a layer of nickel is plated on the surface of the graphite electrodes.

[0030] In some embodiments of the present disclosure, the measuring electrodes M and N are graphite electrodes, and a layer of nickel is plated on the surface of the graphite electrodes.

[0031] In some embodiments of the present disclosure, the electrical measuring instrument is installed on an adjustable mobile support, the adjustable mobile support comprising walking wheels arranged on both sides of the diaphragm wall, left and right supports arranged on both sides of the diaphragm wall being connected to the walking wheels, and a transverse telescopic rod being connected between the left and right supports, so that the telescopic length of the transverse telescopic rod can be adjusted to adapt to different widths of the diaphragm wall. Advantages

[0032] The present disclosure uses resistivity imaging technology to achieve non-destructive detection of the diaphragm wall joint, avoiding the damage caused by drilling or damaging the wall in traditional methods. Through the electrode device and resistivity imaging technology, the resistivity distribution map of the diaphragm wall joint area can be accurately drawn, and the leakage position can be accurately determined, thereby improving the accuracy and reliability of the detection.

[0033] The detection method is simple in steps and easy to operate, and is suitable for leakage detection of various diaphragm wall projects, which not only reduces the complexity of operation, but also greatly improves the work efficiency. Compared with the traditional drilling core method and acoustic transmission method, the present disclosure significantly reduces the damage to the wall and reduces the repair cost, thereby making the overall detection cost lower and protecting the integrity of the engineering structure.

[0034] The resistivity imaging technology is used to detect the leakage of the diaphragm wall joint. By arranging electrodes around the diaphragm wall, power is supplied to the diaphragm wall and the surrounding rock, and the potential difference signal is received by the measuring electrodes to draw the resistivity distribution map of the diaphragm wall joint area, thereby determining the leakage position. The non-destructive feature does not cause any physical damage to the diaphragm wall during the detection process, and the entire wall, especially the joint area, can be comprehensively detected to provide accurate and reliable leakage information and timely detection results.

[0035] By measuring the resistivity change of the underground material, the resistivity distribution of the underground continuous wall is drawn, so that the leakage point is found. The resistivity imaging technology not only has the characteristics of high precision and high resolution, can provide detailed internal information of the wall, the detection range of the resistivity imaging technology is wide, can cover the joint area of the whole underground continuous wall, and provides comprehensive detection results.

[0036] The matched electrode material adopts the mode that the surface of the graphite electrode is plated with nickel. The graphite has low resistivity and can withstand high temperature. The nickel plating layer on the surface of the graphite not only can enhance the mechanical strength of the graphite electrode, make it more wear-resistant and not easy to be damaged, but also can protect the graphite electrode, prevent corrosion, reduce polarization phenomenon, reduce direct contact between the electrode and the medium, reduce electrolysis and polarization phenomenon, and improve the accuracy and stability of measurement. BRIEF DESCRIPTION OF DRAWINGS

[0037] Fig. 1 is a schematic structural diagram of a detection scene of a joint leakage resistivity tomography of an underground continuous wall;

[0038] Fig. 2 is a schematic diagram of a detection point arrangement;

[0039] Fig. 3 is a block diagram of the working process of an electrical measuring instrument;

[0040] Fig. 4 is a schematic diagram of an adjustable moving support structure;

[0041] Names of components in the figure: 1, electrical measuring instrument; 2, transmitter; 3, receiver; 4, power supply electrode A; 5, power supply electrode B; 6, measurement electrode M; 7, measurement electrode N; 8, foundation pit; 9, drill hole; 10, diaphragm wall; 11, detection point; 12, adjustable moving support; 13, walking wheel; 14, left support; 15, right support; 16, transverse telescopic rod. Best embodiment of the present application

[0042] The example discloses a joint leakage resistivity tomography detection method of an underground continuous wall, referring to Figs. 1 to 4, comprising the following steps:

[0043] S1, selecting a joint area to be detected: after the construction of the underground continuous wall is completed, before the foundation pit 8 is excavated, the joint area to be detected is selected and the environment of the foundation pit 8 is evaluated;

[0044] S2, drilling a hole 9 and arranging a power supply electrode: drilling a hole 9 at the center position of the foundation pit 8, the depth of the hole 9 is less than the depth of the foundation pit 8, arranging a power supply electrode A 4 at the bottom of the hole 9, and arranging a power supply electrode B 5 at a position at least one time the length of the foundation pit 8 away from the center of the foundation pit 8;

[0045] S3, arranging a plurality of detection points 11: arranging a plurality of detection points 11 along the extension direction of the underground continuous wall on the ground around the foundation pit 8, the distance between adjacent detection points 11 is d p , and arranging a measuring electrode M6 and a measuring electrode N7 at each detection point 11 in the direction perpendicular to the underground continuous wall, the distance between the measuring electrode M6 and the measuring electrode N7 is l MN , and respectively located on both sides of the underground continuous wall 10;

[0046] S4, signal measurement: the power supply electrode A4 is connected to the transmitter 2 of the electrical measuring instrument 1, the measuring electrode M6 and the measuring electrode N7 are connected to the receiver 3 of the electrical measuring instrument 1, the electrical measuring instrument 1 is started, the power supply electrode supplies power to the underground continuous wall and the surrounding rock and soil, the measuring electrode receives the potential difference signal and records the data;

[0047] S5, judging the leakage point: processing the collected potential difference data to draw the resistivity distribution map of the joint area of the underground continuous wall, so as to judge the position and range of the leakage point.

[0048] The purpose of evaluating the environment of the foundation pit 8 is to ensure that the environment of the foundation pit 8 is suitable for arranging the electrode device, and there is no other interference source affecting the resistivity measurement;

[0049] The evaluation of the environment of the foundation pit 8 in step S1 includes the following steps:

[0050] a. Review the construction record: review the construction record of the underground continuous wall, the design, construction process and material use of the joint, identify the joint area with problems,

[0051] such as those areas with difficult construction, unstable material performance or problems in the construction process;

[0052] b. Appearance inspection: comprehensively inspect the cracks, benching appearance defects of the underground continuous wall, and preliminarily determine the joint areas that need to be detected according to the results of the appearance inspection;

[0053] c. Determine the detection joint area: analyze the stress condition and potential leakage path of the underground continuous wall combined with the geological survey report and design drawing; according to the underground water level, soil property and surrounding environmental factors, evaluate the risk of the joint to determine the final detection joint area;

[0054] d. Clean the environment of the foundation pit 8: before the excavation of the foundation pit 8, evaluate the environmental conditions in the foundation pit 8, including the underground water level, soil stability and harmful gas factors; if there is water accumulation or loose soil in the foundation pit 8, first carry out drainage and soil reinforcement to ensure the dryness and stability of the electrode arrangement area, and clean the sundries, garbage and loose soil in the foundation pit 8 to provide a flat working surface for the installation of the electrode device.

[0055] The drilling 9 in step S2 includes the following steps:

[0056] The drilling 9 is performed at the center of the foundation pit 8 using a drilling machine, and the bottom of the drilling 9 is not more than the measuring distance of the electrode from the bottom of the foundation pit 8, so that the electrode can reach the measuring layer; after the drilling 9 is completed, the debris and mud in the hole are cleaned to keep the inside of the drilling 9 clean;

[0057] The arrangement of the power supply electrode in step S2 includes the following steps:

[0058] a. Installing the power supply electrode A4: the power supply electrode A4 is installed into the drilling 9 by means of an electrode installation tool, and conductive glue or filling material is used to reduce the contact resistance to ensure that the electrode is in close contact with the wall of the drilling 9; and the electrode is fixed in the drilling 9 with cement or other fixing materials to prevent the electrode from being displaced due to external forces;

[0059] b. Installing the power supply electrode B5: according to the length of the foundation pit 8, the power supply electrode B5 is calculated to be located at a position at least one length of the foundation pit 8 from the foundation pit 8; the power supply electrode B5 and the power supply electrode A4 are in a straight line relationship to ensure uniform distribution of the current field; the drilling 9 operation and installation process are repeated according to the foregoing steps at the determined position to install the power supply electrode B5;

[0060] c. Connecting the electrical measuring instrument 1 and checking: the power supply electrode A4 and the power supply electrode B5 are connected to the transmitter 2 of the electrical measuring instrument 1, and the circuit is checked for smoothness; after the electrode arrangement work is completed, a safety check is performed to ensure that the electrodes and the connecting wires are safe and reliable to avoid threatening the construction personnel or equipment.

[0061] The arrangement of a plurality of detection points 11 in step S3 includes the following steps:

[0062] According to the size of the foundation pit 8 and the layout of the underground continuous wall, the positions of each detection point 11 are marked on the ground, and a drilling machine is used to drill a drilling 9 at the corresponding detection point 11 position so that the drilling 9 depth reaches the expected measuring layer, and then a measuring electrode M6 and a measuring electrode N7 are installed into the drilling 9, and the actual distance between the measuring electrode M6 and the measuring electrode N7 depends on the thickness of the diaphragm wall 10; conductive glue or filling material is used to ensure that the electrode is in close contact with the wall of the drilling 9 to reduce the contact resistance, and cement or other fixing materials are used to fix the electrode to prevent it from moving due to external forces.

[0063] The signal measurement in step S4 includes the following steps: starting the electrical measuring instrument 1, performing system self-checking to ensure that the instrument is working properly; supplying power to the underground continuous wall and the surrounding rock-soil mass through the power supply electrodes A4 and B to create a stable current field; measuring the potential difference signal caused by the current field by the electrodes M6 and N, and recording the measurement data in real time by the electrical measuring instrument 1, including the potential difference value, the measurement time, and the environmental conditions; preliminarily analyzing the data to check their consistency and reliability, and finally transmitting the data to a computer for further processing and analysis using ERT imaging software to reconstruct the resistivity distribution image.

[0064] The judgment of the leakage point in step S5 includes the following steps:

[0065] a. Data processing and resistivity calculation: first, check the consistency and completeness of the data to exclude obviously incorrect measurement data to ensure data quality; then, remove outliers caused by external interference or instrument failure; subsequently, perform standardization processing on the data to eliminate the influence of systematic errors and background noise; during data processing, select appropriate inversion algorithms, including least squares method, conjugate gradient method or nonlinear inversion algorithm, to reconstruct the resistivity distribution from the potential difference data; apply the selected algorithm to process the data to calculate the resistivity of the underground continuous wall and the surrounding rock-soil mass;

[0066] b. Inversion and reconstruction of resistivity: import the processed data into the ERT special software and set the inversion parameters, including the position of the measurement electrodes, the electrode spacing and the geological structure; after running the software, reconstruct the resistivity distribution map according to the inversion results; perform smoothing processing or adjustment on the image to improve its readability and accuracy;

[0067] c. Leakage evaluation and suggestions: identify the areas of abnormal resistivity on the resistivity distribution map, determine the position of the leakage point according to the position and range of the abnormal resistivity, and analyze the shape and size of the abnormal area to evaluate the range and severity of the leakage; record the resistivity distribution map, the position and range of the leakage point in the report, and make appropriate repair or monitoring suggestions according to the analysis results.

[0068] An underground continuous wall joint leakage electrical resistivity tomography device, comprising an electrical measuring instrument 1 erected above the underground continuous wall 10, the electrical measuring instrument 1 comprising a transmitter 2 and a receiver 3, the transmitter 2 being electrically connected to a power supply electrode A4 and a power supply electrode B5, the power supply electrode A4 being located at the center of the foundation pit 8, and the power supply electrode B5 being located at a position at least one time the length of the foundation pit 8 away from the center of the foundation pit 8; the receiver 3 being electrically connected to a plurality of monitoring components, the monitoring components being arranged on the ground and around the foundation pit 8 along the extension direction of the underground continuous wall, the monitoring components comprising a measurement electrode M6 and a measurement electrode N7 arranged on both sides of the underground continuous wall 10 along the direction perpendicular to the underground continuous wall,

[0069] The power supply electrode A4 and the power supply electrode B5 are graphite electrodes, and a layer of nickel is plated on the surface of the graphite electrodes.

[0070] The measurement electrode M6 and the measurement electrode N7 are graphite electrodes, and a layer of nickel is plated on the surface of the graphite electrodes.

[0071] The electrical measuring instrument 1 is installed on the adjustable mobile support 12, which includes the walking wheels 13 arranged on both sides of the diaphragm wall 10, the left support 14 and the right support 15 arranged on both sides of the diaphragm wall 10, and the transverse telescopic rod 16 connected between the left support 14 and the right support 15. The telescopic length of the transverse telescopic rod 16 is adjusted to adapt to the width of the diaphragm wall 10.

[0072] During the working process, the electrical measuring instrument 1 is installed on the adjustable mobile support 12. Before starting the detection, the telescopic length of the transverse telescopic rod 16 is adjusted according to the actual width of the diaphragm wall 10 to ensure that the mobile support is stably supported on both sides of the diaphragm wall 10. The mobile support 12 can move on both sides of the diaphragm wall 10 through the walking wheels 13, so that the electrical measuring instrument 1 moves together with the mobile support 12 to perform the resistivity measurement. With the movement of the mobile support 12, the electrical measuring instrument 1 automatically collects the data of each detection point and records them for subsequent analysis.

Claims

1. A method of detecting a joint leakage of a diaphragm wall by electrical resistance tomography, characterized by, The method comprises the following steps: S1, selecting the joint area to be detected: after the construction of the underground continuous wall is completed and before the excavation of the foundation pit, the joint area to be detected is selected and the foundation pit environment is evaluated; S2, drilling and arranging power supply electrodes: a drill hole is constructed at the center position of the foundation pit, the depth of the drill hole is less than the depth of the foundation pit, a power supply electrode A is arranged at the bottom of the drill hole, and a power supply electrode B is arranged at a position at least one time the length of the foundation pit away from the center of the foundation pit; S3, arranging a plurality of detection points: arranging a plurality of detection points along the extension direction of the underground continuous wall on the ground, surrounding the foundation pit, the distance between adjacent detection points is d p , and arranging measuring electrode M and measuring electrode N in the direction perpendicular to the underground continuous wall at each detection point, the distance between measuring electrode M and measuring electrode N is l MN , and respectively located on both sides of the underground continuous wall; S4, signal measurement: the power supply electrode A is connected to the transmitter of the electrical measuring instrument, the measuring electrode M and the measuring electrode N are connected to the receiver of the electrical measuring instrument, the electrical measuring instrument is started, power is supplied to the underground continuous wall and the surrounding rock and soil through the power supply electrode, the potential difference signal is received by the measuring electrode, and data is recorded; S5, judging the leakage point: the collected potential difference data is processed, the resistivity distribution map of the joint area of the underground continuous wall is drawn, and the position and range of the leakage point are judged; a. Data processing and calculation of resistivity: first, check the consistency and integrity of the data, exclude obviously incorrect measurement data to ensure data quality; then remove outliers caused by external interference or instrument failure; then standardize the data to eliminate the influence of systematic errors and background noise; during data processing, select appropriate inversion algorithms, including least squares method, conjugate gradient method or nonlinear inversion algorithm, to reconstruct the resistivity distribution from the potential difference data; process the data by applying the selected algorithm to calculate the resistivity of the underground continuous wall and the surrounding rock mass; b. Inversion and reconstruction of resistivity: import the processed data into the ERT special software and set the inversion parameters, including the position of the measuring electrode, the electrode spacing and the geological structure; after running the software, the resistivity distribution map is reconstructed according to the inversion result; the image is smoothed or adjusted to improve the readability and accuracy of the image; c. Leakage evaluation and suggestion: identify the area with abnormal resistivity on the resistivity distribution map, determine the position of the leakage point according to the position and range of the abnormal resistivity, and analyze the shape and size of the abnormal area to evaluate the range and severity of the leakage; record the resistivity distribution map, the position and range of the leakage point in the report, and make appropriate repair or monitoring suggestions according to the analysis result.

2. The underground diaphragm wall joint leakage electrical resistivity tomography detection method of claim 1, wherein: The evaluation of the foundation pit environment in step S1 comprises the following steps: a. Review construction records: review the construction records of the underground continuous wall, the design, construction process and material usage of the joint, identify the joint area with problems, b. Appearance inspection: conduct a comprehensive inspection of the cracks, dislocation and other appearance defects of the underground continuous wall, and preliminarily determine the joint areas that need to be detected according to the results of the appearance inspection; c. Determine the detection joint area: analyze the stress condition and potential leakage path of the underground continuous wall in combination with the geological survey report and design drawings; evaluate the risk of the joint according to the groundwater level, soil properties and surrounding environmental factors to determine the final detection joint area; d. Clean up the foundation pit environment: Before the foundation pit is excavated, the environmental conditions in the foundation pit are evaluated, including the underground water level, soil stability, and harmful gas factors. If there is accumulated water or soft soil in the foundation pit, drainage and soil reinforcement should be carried out to ensure the dryness and stability of the electrode arrangement area, and the debris, garbage and loose soil in the foundation pit should be cleaned up to provide a flat working surface for the installation of the electrode device.

3. The underground diaphragm wall joint leakage electrical resistance tomography detection method of claim 1, wherein: The drilling in the step S2 includes the following steps: Use a drilling machine to drill at the center position of the foundation pit. The bottom of the drill hole is not more than the measuring distance of the electrode from the bottom of the foundation pit to achieve the electrode to touch the measuring layer. After the drilling is completed, the debris and mud in the hole are cleaned to keep the inside of the drill hole clean.

4. The underground diaphragm wall joint leakage electrical resistivity tomography detection method of claim 1, wherein: The step S2 includes the following steps: a. Install the power supply electrode A: install the power supply electrode A into the drill hole with the help of electrode installation tools, use conductive glue or filling material to reduce contact resistance to ensure that the electrode is in close contact with the drill hole wall, and use cement or other fixing materials to fix the electrode in the drill hole to prevent the electrode from being displaced due to external force; b. Install the power supply electrode B: according to the length of the foundation pit, calculate the position of the power supply electrode B at a position at least one time the length of the foundation pit; the position of the power supply electrode B and the power supply electrode A maintains a straight line relationship to ensure uniform distribution of the current field; repeat the drilling operation and installation process according to the foregoing steps at the determined position to install the power supply electrode B; c. Connect the electrical measuring instrument and check: connect the power supply electrode A and the power supply electrode B with the transmitter of the electrical measuring instrument and check the circuit for smoothness; after the electrode arrangement work is completed, safety check is carried out to ensure that the electrode and the connecting line are safe and reliable to avoid threatening the construction personnel or equipment.

5. The method of claim 1, wherein: The step S3 includes the following steps: according to the size of the foundation pit and the layout of the underground continuous wall, mark the position of each detection point on the ground, and use a drilling machine to drill at the corresponding detection point position to make the drill hole depth reach the expected measuring layer, then install the measuring electrode M and the measuring electrode N into the drill hole, use conductive glue or filling material to ensure that the electrode is in close contact with the drill hole wall to reduce contact resistance, and use cement or other fixing materials to fix the electrode to prevent it from moving due to external force.

6. The underground diaphragm wall joint leakage electrical resistivity tomography detection method of claim 1, wherein: The signal measurement in the step S4 includes the following steps: start the electrical measuring instrument, perform system self-checking to ensure that the instrument is working properly; supply power to the underground continuous wall and the surrounding rock-soil mass through the power supply electrodes A and B to create a stable current field; the measuring electrodes M and N detect the potential difference signal caused by the current field, and the electrical measuring instrument records the measurement data in real time, including the potential difference value, the measurement time, and the environmental conditions; preliminarily analyze the data to check its consistency and reliability, and finally transmit the data to a computer for further processing and analysis using ERT imaging software to reconstruct the resistivity distribution image.

7. A diaphragm wall joint leakage electrical resistance tomography device for implementing the diaphragm wall joint leakage electrical resistance tomography detection method according to claim 1, characterized in that, The electric measuring instrument comprises a transmitter and a receiver, the transmitter is electrically connected with a power supply electrode A and a power supply electrode B, the power supply electrode A is located at the center of the foundation pit, and the power supply electrode B is located at a position away from the center of the foundation pit by at least one length of the foundation pit; the receiver is electrically connected with a plurality of monitoring components, the monitoring components are arranged on the ground and around the foundation pit along the extension direction of the underground continuous wall, and the monitoring components comprise a measuring electrode M and a measuring electrode N arranged on both sides of the underground continuous wall along the vertical direction of the underground continuous wall.

8. The diaphragm wall joint leakage electrical resistivity tomography apparatus of claim 7, wherein: The power supply electrode A and the power supply electrode B are graphite electrodes, and the graphite electrodes are plated with a layer of nickel on the surface; the measuring electrode M and the measuring electrode N are graphite electrodes, and the graphite electrodes are plated with a layer of nickel on the surface.

9. The diaphragm wall joint leakage electrical resistivity tomography apparatus of claim 7, wherein: The electric measuring instrument is installed on an adjustable moving support, the adjustable moving support comprises walking wheels arranged on both sides of the underground continuous wall, left supports and right supports arranged on both sides of the underground continuous wall are connected on the walking wheels, the left supports and the right supports are connected through a transverse telescopic rod, and the telescopic length of the transverse telescopic rod is adjusted to adapt to different widths of the underground continuous wall.

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