Underground space time-shifting transient electromagnetic unmanned monitoring device and method

Abstract

The invention discloses an underground space time-shifting transient electromagnetic unmanned monitoring device and method. The underground space time-shifting transient electromagnetic unmanned monitoring device comprises a mobile platform, a multifunctional transient electromagnetic detection device and a ground remote control terminal, the multifunctional transient electromagnetic detection device can actively adjust the distance between a transmitting coil and a receiving coil so as to realize a mutual inductance eliminating 8-shaped coil structure, and through cooperation with a calibration algorithm of a control center, the automation level and reliability of detection are remarkably improved, and it is ensured that the 8-shaped coil is in a mutual inductance eliminating state. In addition, the transient electromagnetic monitoring device can perform structure switching between deep layer detection and shallow layer detection, so that a high-efficiency detection mode that one circle has two purposes is realized, and the efficiency and the flexibility of detection operation are remarkably improved. In the actual detection process, the advantages that the 8-shaped coil is small in shallow blind area and large in overlapped loop detection depth are fully played, advantage complementation of two coil modes is achieved, and comprehensiveness and accuracy of a detection result are remarkably improved through a data fusion mode.

Description

Technical Field

[0001] The present invention relates to an underground space time-lapse transient electromagnetic unmanned monitoring device and method, belonging to the technical field of underground space detection. Background Art

[0002] In the context of the rapid development of urbanization and the increasing demand for underground space resources, the exploration, evaluation, and reuse of abandoned and hidden underground spaces have become important technical challenges in urban planning. The inherent properties of underground spaces, including the complexity of their structures, the concealment of their locations, and the potential hazards of their environments, pose severe challenges to traditional detection technologies.

[0003] Currently, the detection of underground spaces can be divided into surface and above-ground detection and in-depth detection inside the underground space. Surface and above-ground detection is often interfered with by the surface covering layer and ground structures, resulting in impaired detection accuracy; in-depth detection methods inside the underground space have higher accuracy, and they can be further divided into manual detection and unmanned detection. Comparatively speaking, manual detection requires a relatively high level of operation skills for technicians and has potential risks; with the development of unmanned technologies, underground space detection based on unmanned platforms has gradually shown significant advantages. Existing unmanned underground space detection technologies mostly use unmanned equipment equipped with lidar, visual sensors, transient electromagnetic devices, etc. to carry out detection operations. However, lidar and visual sensors can only achieve surface perception detection of underground spaces and are difficult to penetrate the surface to detect abnormal bodies hidden beneath. In contrast, the transient electromagnetic method has strong penetration ability, high sensitivity to low-resistance abnormal bodies, high construction efficiency, and low cost, and has been widely used in the field of underground space detection. However, existing transient electromagnetic coil devices have many limitations during the detection process: traditional multi-turn loop devices have a large shallow blind area, while the figure-eight overlapping loop can reduce the shallow blind area, but the detection depth is limited, and the coil is also easily disturbed and deformed during the detection process. This not only reduces the detection efficiency but also affects the reliability of the detection results.

[0004] Therefore, how to provide a new monitoring device and method that can avoid the potential risks faced by technicians during underground space construction, can independently complete the debugging and calibration of the coil device, simultaneously achieve accurate detection of shallow and deep layers, dynamically monitor potential abnormal bodies and hazard sources in the underground space, and ultimately achieve unmanned, high-efficiency, and high-precision detection of the underground space is the research direction required by the present invention. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides an underground space time-lapse transient electromagnetic unmanned monitoring device and method, which can not only avoid the potential dangers faced by technicians when entering the underground space for construction, but also autonomously complete the debugging and calibration of the coil device, and at the same time achieve accurate detection of shallow and deep layers, dynamically monitor potential abnormal bodies and hazard sources in the underground space, and finally realize unmanned, high-efficiency and high-precision detection of the underground space.

[0006] To achieve the above object, the technical solution adopted by the present invention is: an underground space time-lapse transient electromagnetic unmanned monitoring device, including a mobile platform, a multi-functional transient electromagnetic detection device and a ground remote control terminal;

[0007] The multi-functional transient electromagnetic detection device includes a load-bearing bracket, a rotating shaft, a rotating motor, a transient electromagnetic transmitting coil, a transient electromagnetic receiving coil, an electric telescopic rod and a transient electromagnetic host; the transient electromagnetic transmitting coil is fixed on the lower surface of the load-bearing bracket, the transient electromagnetic receiving coil is placed on the upper surface of the load-bearing bracket, one end of the electric telescopic rod is fixedly connected to the upper surface of the load-bearing bracket, and the other end is connected to the transient electromagnetic receiving coil, and is used to drive the transient electromagnetic receiving coil to move on the upper surface of the load-bearing bracket; the rotating motor is installed inside the mobile platform, the load-bearing bracket is connected to the rotating motor through the rotating shaft, and the rotating motor can drive the load-bearing bracket to rotate relative to the mobile platform to adjust the detection directions of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil; the transient electromagnetic host is installed on the mobile platform and is respectively connected to the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil through communication lines, and is used to control the transient electromagnetic transmitting coil to emit electromagnetic signals and store the electromagnetic data received by the transient electromagnetic receiving coil;

[0008] The control center of the mobile platform is used to control the start and stop of the transient electromagnetic host, the rotating motor and the electric telescopic rod, and at the same time it sends the data stored by the transient electromagnetic host to the ground remote control terminal through a wireless communication module;

[0009] The ground remote control terminal is used to send instructions to the control center to control the poses of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil; when performing deep detection, the centers of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil overlap vertically; when performing shallow detection, the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil form an 8-shaped coil vertically.

[0010] Further, a sliding groove is installed on the upper surface of the load-bearing bracket, a sliding block is installed in the sliding groove, and the transient electromagnetic receiving coil is fixed on the upper part of the sliding block, so that the transient electromagnetic receiving coil moves along the sliding groove direction through the sliding block. Such a setting is convenient for the electric telescopic rod to drive the transient electromagnetic receiving coil to adjust the relative position with the transient electromagnetic transmitting coil when stretching and retracting, so as to achieve deep detection or shallow detection.

[0011] Further, the load-bearing bracket is made of non-metallic material, which will not affect the accuracy of data acquisition in transient electromagnetic detection.

[0012] Further, the mobile platform is a fully automatic unmanned robot or a remotely controlled robot.

[0013] Further, the planes where the transient electromagnetic emission coil and the transient electromagnetic reception coil are located are parallel to each other; both the transient electromagnetic emission coil and the transient electromagnetic reception coil are circular rings and have the same diameter.

[0014] The working method of the above underground space time-lapse transient electromagnetic unmanned monitoring device is specifically as follows:

[0015] Step 1: Determine the site model and the layout of survey lines: Before the detection operation starts, first use an unmanned device with a lidar scanner to scan the underground space comprehensively to construct a three-dimensional model of the underground space, and based on this model, plan the survey lines and the layout of each measuring point on the survey lines.

[0016] Step 2: Equipment debugging and calibration: Before entering the underground space, first debug and calibrate the figure-eight coil for shallow detection. In the state of the figure-eight coil, manually control the transient electromagnetic reception coil to be finely adjusted relative to the transient electromagnetic emission coil to the theoretical mutual inductance cancellation state and collect signals, and use this signal as the reference signal. After entering the underground space, the ground remote control terminal sends an instruction, and the control center controls the electric telescopic rod to make the transient electromagnetic reception coil move horizontally. During this process, the transient electromagnetic host controls the transient electromagnetic emission coil to emit electromagnetic signals, and obtains the electromagnetic data received by the transient electromagnetic reception coil for test detection, and compares the detection result with the reference signal and continuously corrects the position of the transient electromagnetic reception coil until the error from the reference signal is less than the preset threshold, and keeps the current position of the transient electromagnetic reception coil.

[0017] Step 3: Carry out shallow detection operations: The mobile platform starts detection according to the survey lines and the positions of each measuring point on the survey lines planned in Step 1, and initially keeps the plane where the transient electromagnetic emission coil is located parallel to the ground. When the mobile platform reaches the first measuring point, it stops. The transient electromagnetic host conducts a primary detection of the bottom plate of the underground space through the figure-eight coil, and then the control center controls the rotary motor to rotate the figure-eight coil by 90° to be perpendicular to the ground, and the transient electromagnetic host conducts a primary detection of the side wall or side of the underground space. After completion, the mobile platform moves to the next measuring point, and during the movement, the figure-eight coil is restored to the initial state. The detection process of the first measuring point is repeated for each subsequent measuring point until all the shallow detection work of all measuring points is completed, and the control center transmits the data to the ground remote control terminal.

[0018] Step 4. Coil form switching: After receiving the data from the shallow detection, the ground remote control terminal sends an instruction. After receiving the instruction, the control center controls the telescopic movement of the electric telescopic rod, so that the transient electromagnetic emission coil and the transient electromagnetic receiving coil are switched to an overlapping loop and maintained;

[0019] Step 5. Conduct deep detection operations: The mobile platform returns along the survey line and the positions of each measuring point on the survey line planned in Step 1 for deep detection. Initially, the plane where the transient electromagnetic emission coil is located is kept parallel to the ground. When the mobile platform reaches the first measuring point, it stops. The transient electromagnetic main machine conducts a primary detection of the bottom plate of the underground space through the overlapping loop. Subsequently, the control center controls the rotary motor to rotate the overlapping loop by 90° to be perpendicular to the ground, and the transient electromagnetic main machine conducts a primary detection of the side wall or side of the underground space; after completion, the mobile platform moves to the next measuring point, and the overlapping loop is restored to the initial state during the movement; the detection process of the first measuring point is repeated for each subsequent measuring point until the deep detection work of all measuring points is completed, and the control center transmits the data to the ground remote control terminal;

[0020] Step 6. Data fusion processing: The ground remote control terminal separately conducts data fusion processing on the shallow data and deep data obtained from each measuring point, and generates a apparent resistivity map of the underground space according to the results of the data fusion;

[0021] Step 7. Time-lapse transient electromagnetic method monitoring: Set the detection interval according to the actual situation and conduct periodic detection operations; the survey line and measuring points for each detection operation remain unchanged, and Steps 2 to 6 are repeated; after each periodic detection is completed, the time-lapse algorithm of the transient electromagnetic method is used to calculate the data obtained from different periodic detections, which is used to infer the physical property evolution of abnormal bodies around the underground space on different time scales.

[0022] Furthermore, in Step 6, the data fusion processing refers to performing time-depth conversion on the data of shallow detection and deep detection of each measuring point on the same survey line through the smoke ring inversion theory, and then extracting the shallow [0’ D1) data of the shallow detection data set and the deep [D1’ D2] data of the deep detection data set, and recombining these two parts of data according to the principle of one-to-one correspondence of the same measuring point on the same survey line to obtain the [0’ D2] data as the final data set of this survey line; where D1 and D2 respectively represent the depth of shallow detection and the depth of deep detection, with the unit of meter, and D2 is greater than D1.

[0023] Furthermore, when using the time-lapse algorithm of the transient electromagnetic method to calculate the data obtained from different periodic detections in Step 7, specifically:

[0024] Assume that for the same measuring point in the underground space at different periodic times t1, t2,..., t n n detections are carried out, and the forward equation for each detection is expressed as:

[0025]

[0026] Among them, is the electrical model parameter of the underground space at time t (such as resistivity distribution), i and is the observation data at time t i (induced electromotive force decay curve), and f is the transient electromagnetic forward operator;

[0027] Through the inversion algorithm (such as the least squares method), the resistivity distribution at each time is obtained:

[0028]

[0029] Taking the initial time t1 as the reference benchmark, the resistivity change rate at the subsequent time t i is:

[0030]

[0031] By calculating and analyzing of the change trend, the dynamic change characteristics of abnormal media in the underground space can be identified.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. The transient electromagnetic monitoring device of the present invention can actively adjust the distance between the transmitting coil and the receiving coil to achieve an 8-shaped coil structure for eliminating mutual inductance. During the detection operation, the device can autonomously complete debugging and calibration through an electric telescopic rod, and cooperate with the calibration algorithm of the control center, significantly improving the automation level and reliability of detection, and ensuring that the 8-shaped coil is in a state of eliminating mutual inductance.

[0034] 2. The transient electromagnetic monitoring device of the present invention can perform structural switching between deep detection and shallow detection. When performing deep detection, the centers of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil overlap vertically; when performing shallow detection, the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil form an 8-shaped coil vertically; thus realizing an efficient detection mode of "one coil for two uses", significantly improving the efficiency and flexibility of the detection operation; during the actual detection process, the advantages of the 8-shaped coil with a small shallow blind area and the overlapping loop with a large detection depth are fully utilized, realizing the complementary advantages of the two coil modes, and significantly improving the comprehensiveness and accuracy of the detection results through data fusion.

[0035] 3. During the full-cycle detection process of the present invention, time-lapse transient electromagnetic method is adopted, realizing dynamic monitoring and data accumulation of potential abnormal bodies and hazard sources in underground space. Traditional one-time detection methods can only obtain static information of abnormal bodies and are difficult to reflect their evolution characteristics over time. In contrast, through periodic and continuous detection operations, the present invention can track the dynamic change process of underground abnormal bodies or hazard sources in real time, capture the evolution of their physical properties on different time scales, and then predict and evaluate the development trend of abnormal bodies or hazard sources. It saves labor costs and provides more comprehensive information support for the safety assessment and risk early warning of underground space. Brief Description of the Drawings

[0036] Figure 1 is a schematic structural diagram when the device of the present invention conducts shallow detection downward;

[0037] Figure 2 is a schematic structural diagram when the device of the present invention conducts shallow detection to the side;

[0038] Figure 3 is a schematic structural diagram when the device of the present invention conducts deep detection downward;

[0039] Figure 4 is a schematic structural diagram when the device of the present invention conducts deep detection to the side;

[0040] Figure 5 is an overall schematic diagram of the detection operation of the present invention.

[0041] In the figure: 1 - Transient electromagnetic emission coil, 2 - Transient electromagnetic receiving coil, 3 - Load-bearing bracket, 4 - Slide groove, 5 - Slide block, 6 - Electric telescopic rod, 7 - Rotating shaft, 8 - Transient electromagnetic main unit, 9 - Control center, 10 - Wireless communication module. Detailed Embodiment

[0042] The present invention will be further described below.

[0043] As shown in the figure, a time-lapse transient electromagnetic unmanned monitoring device for underground space includes a mobile platform, a multi-functional transient electromagnetic detection device, and a ground remote control terminal;

[0044] The multifunctional transient electromagnetic detection device includes a load-bearing bracket 3, a rotating shaft 7, a rotating motor, a transient electromagnetic transmitting coil 1, a transient electromagnetic receiving coil 2, an electric telescopic rod 6, and a transient electromagnetic main unit 8. The transient electromagnetic transmitting coil 1 is fixed on the lower surface of the load-bearing bracket 3, and the transient electromagnetic receiving coil 2 is placed on the upper surface of the load-bearing bracket 3. One end of the electric telescopic rod 6 is fixedly connected to the upper surface of the load-bearing bracket 3, and the other end is connected to the transient electromagnetic receiving coil 2, which is used to drive the transient electromagnetic receiving coil 2 to move on the upper surface of the load-bearing bracket 3. The rotating motor is installed inside the mobile platform. The load-bearing bracket 3 is connected to the rotating motor through the rotating shaft 7, and the rotating motor can drive the load-bearing bracket 3 to rotate relative to the mobile platform to adjust the detection directions of the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2. The transient electromagnetic main unit 8 is installed on the mobile platform and is connected to the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2 respectively through communication lines, which is used to control the transient electromagnetic transmitting coil 1 to emit electromagnetic signals and store the electromagnetic data received by the transient electromagnetic receiving coil 2. The planes where the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2 are located are parallel to each other. Both the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2 are circular rings and have the same diameter.

[0045] The control center 9 of the mobile platform is used to control the start and stop of the transient electromagnetic main unit 8, the rotating motor, and the electric telescopic rod 6. At the same time, it sends the data stored in the transient electromagnetic main unit 8 to the ground remote control terminal through the wireless communication module 10.

[0046] The ground remote control terminal is used to send instructions to the control center 9 to control the postures of the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2. When performing deep detection, the centers of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil overlap vertically as shown in Figure 3 and 4 ; when performing shallow detection, the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil are in an 8-shaped coil vertically as shown in Figure 1 and 2 .

[0047] As an improvement of the present invention, a chute 4 is installed on the upper surface of the load-bearing bracket 3, and a slider 5 is installed in the chute 4. The transient electromagnetic receiving coil 2 is fixed on the upper part of the slider 4, so that the transient electromagnetic receiving coil 2 moves along the direction of the chute 4 through the slider 5. Such a setting facilitates the telescopic movement of the electric telescopic rod 6 to drive the transient electromagnetic receiving coil 2 to adjust the relative position with the transient electromagnetic transmitting coil 1, so as to realize deep detection or shallow detection. The load-bearing bracket 3 is made of non-metallic material. This will not affect the accuracy of the data obtained by transient electromagnetic detection. The mobile platform is an existing device, which can be a fully automatic unmanned robot or a remotely controlled robot; both the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2 are wound with a coil skeleton printed by 3D printing, and its structural stability is excellent, and it can maintain a stable shape in a complex use environment, avoiding the decrease of detection accuracy due to deformation.

[0048] As Figure 5 shown, the working method of the above underground space time-lapse transient electromagnetic unmanned monitoring device is specifically as follows:

[0049] Step 1: Determine the site model and survey line position planning: Before the detection operation starts, first use an unmanned device with a lidar scanner to scan the underground space comprehensively, construct a three-dimensional model of the underground space, and plan the survey line and the position layout of each measuring point on the survey line based on this model;

[0050] Step 2: Equipment debugging and calibration: Before entering the underground space, first debug and calibrate the figure-eight coil during shallow detection. In the state of the figure-eight coil, manually control the transient electromagnetic receiving coil 2 to fine-tune relative to the transient electromagnetic transmitting coil 1 to the theoretical mutual inductance cancellation state and collect signals, and use this signal as the reference signal; after entering the underground space, the ground remote control terminal sends an instruction, and the control center 9 controls the electric telescopic rod 6 to make the transient electromagnetic receiving coil 2 move horizontally. During this process, the transient electromagnetic host 8 controls the transient electromagnetic transmitting coil 1 to emit electromagnetic signals, and obtains the electromagnetic data received by the transient electromagnetic receiving coil 2 for test detection, and compares the detection result with the reference signal and continuously corrects the position of the transient electromagnetic receiving coil 2 until the error from the reference signal is less than the preset threshold (such as 0.1%, which can be calibrated through experiments), and keep the current position of the transient electromagnetic receiving coil 2 as Figure 1 shown;

[0051] Step 3: Carry out shallow detection operations: The mobile platform starts detection according to the survey line and the position of each measuring point on the survey line planned in Step 1, and initially keeps the plane where the transient electromagnetic transmitting coil 1 is located parallel to the ground. When the mobile platform reaches the first measuring point, it stops. The transient electromagnetic host 8 conducts a primary detection on the bottom plate of the underground space through the figure-eight coil, and then the control center 9 controls the rotating motor to rotate the figure-eight coil 90° to be perpendicular to the ground as Figure 2As shown, the transient electromagnetic main unit 8 conducts a single detection on the side wall or side of the underground space. After completion, the mobile platform moves to the next measurement point, and during the movement, the figure-eight coil is restored to its initial state. The detection process of the first measurement point is repeated for each subsequent measurement point until the shallow detection work of all measurement points is completed, and the control center 9 transmits data to the ground remote control terminal.

[0052] Step Four: Coil Shape Switching: After receiving the data of the shallow detection, the ground remote control terminal sends an instruction. After receiving the instruction, the control center 9 controls the telescopic movement of the electric telescopic rod 6, thereby switching the transient electromagnetic transmitting coil 1 and the transient electromagnetic receiving coil 2 into an overlapping loop and maintaining as Figure 3 shown.

[0053] Step Five: Conduct Deep Detection Operations: The mobile platform returns along the survey line and the positions of each measurement point on the survey line planned in Step One for deep detection. Initially, the plane where the transient electromagnetic transmitting coil 1 is located is kept parallel to the ground. When the mobile platform reaches the first measurement point, it stops. The transient electromagnetic main unit 8 conducts a single detection on the bottom plate of the underground space through the overlapping loop. Subsequently, the control center 9 controls the rotating motor to rotate the overlapping loop by 90° to be perpendicular to the ground as Figure 4 shown. The transient electromagnetic main unit 8 conducts a single detection on the side wall or side of the underground space. After completion, the mobile platform moves to the next measurement point, and during the movement, the overlapping loop is restored to its initial state. The detection process of the first measurement point is repeated for each subsequent measurement point until the deep detection work of all measurement points is completed, and the control center 9 transmits data to the ground remote control terminal.

[0054] Step Six: Data Fusion Processing: The ground remote control terminal respectively conducts data fusion processing on the shallow data and deep data obtained from each measurement point, and generates a apparent resistivity map of the underground space based on the results of the data fusion. Data fusion processing refers to performing time-depth conversion on the data of the shallow detection and deep detection of each measurement point on the same survey line through the smoke ring inversion theory, and then extracting the shallow [0’ D1) data of the shallow detection data set and the deep [D1’ D2] data of the deep detection data set, and recombining these two parts of data according to the principle of one-to-one correspondence of the same measurement point on the same survey line to obtain the [0’ D2] data as the final data set of this survey line. Among them, D1 and D2 respectively represent the depth of the shallow detection and the depth of the deep detection, with the unit of meter, and D2 is greater than D1. If there is no other survey line task, a single shallow and deep detection is completed. If there are multiple survey lines, repeat Steps Two to Six until all survey line tasks are completed.

[0055] Step 7. Time-lapse transient electromagnetic method monitoring: Set the detection interval according to the actual situation and carry out periodic detection operations; The survey lines and measurement points for each detection operation remain unchanged, and the above Steps 2 to 6 are repeated; After each periodic detection, use the time-lapse algorithm of the transient electromagnetic method to calculate the data obtained from detections in different periods. Specifically:

[0056] Assume that for the same measurement point in the underground space at different periodic times t1, t2, …, t n n detections are carried out, and the forward modeling equation for each detection is expressed as:

[0057]

[0058] where, is the electrical property model parameter (such as resistivity distribution) of the underground space at time t i , is the observation data (induced electromotive force decay curve) at time t i , and f is the transient electromagnetic forward modeling operator;

[0059] Through the inversion algorithm (such as the least squares method), the resistivity distribution at each time is obtained:

[0060]

[0061] Taking the initial time t1 as the reference benchmark, the resistivity change rate at the subsequent time t i is:

[0062]

[0063] By calculating and analyzing the change trend, the dynamic change characteristics of abnormal media in the underground space can be identified, which can be used to infer the physical property evolution of abnormal bodies around the underground space on different time scales. For example, within the monitoring period: If the of a certain area is negative, that is, the resistivity decreases, it may be caused by groundwater seepage, and the negative anomaly of the change rate indicates the seepage path; If the of a certain area is positive, that is, the resistivity increases, it may be caused by rock mass fracture and crack development, and the positive anomaly of the change rate reflects the crack expansion.

[0064] The above is only the preferred implementation manner of the present invention. It should be noted that: For those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An underground space time-lapse transient electromagnetic unmanned monitoring device, characterized in that, It includes a mobile platform, a multifunctional transient electromagnetic detection device, and a ground remote control terminal; The multifunctional transient electromagnetic detection device includes a load-bearing bracket, a rotating shaft, a rotating motor, a transient electromagnetic transmitting coil, a transient electromagnetic receiving coil, an electric telescopic rod, and a transient electromagnetic host; the transient electromagnetic transmitting coil is fixed on the lower surface of the load-bearing bracket, the transient electromagnetic receiving coil is placed on the upper surface of the load-bearing bracket, one end of the electric telescopic rod is fixedly connected to the upper surface of the load-bearing bracket, and the other end is connected to the transient electromagnetic receiving coil, and is used to drive the transient electromagnetic receiving coil to move on the upper surface of the load-bearing bracket; the rotating motor is installed inside the mobile platform, the load-bearing bracket is connected to the rotating motor through the rotating shaft, and the rotating motor can drive the load-bearing bracket to rotate relative to the mobile platform to adjust the detection directions of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil; the transient electromagnetic host is installed on the mobile platform and is respectively connected to the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil through communication lines, and is used to control the transient electromagnetic transmitting coil to emit electromagnetic signals and store the electromagnetic data received by the transient electromagnetic receiving coil; The control center of the mobile platform is used to control the start and stop of the transient electromagnetic host, the rotating motor, and the electric telescopic rod. At the same time, it sends the data stored by the transient electromagnetic host to the ground remote control terminal through a wireless communication module; The ground remote control terminal is used to send instructions to the control center to control the poses of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil; when performing deep detection, the centers of the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil overlap vertically; when performing shallow detection, the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil form an 8-shaped coil vertically.

2. The underground space time-lapse transient electromagnetic unmanned monitoring device according to claim 1, characterized in that, A chute is installed on the upper surface of the load-bearing bracket, a slider is installed in the chute, and the transient electromagnetic receiving coil is fixed on the upper part of the slider, so that the transient electromagnetic receiving coil moves along the chute direction through the slider.

3. The time-lapse transient electromagnetic unmanned monitoring device for underground space according to claim 1, characterized in that, The load-bearing bracket is made of non-metallic material.

4. The underground space time-lapse transient electromagnetic unmanned monitoring device according to claim 1, wherein The mobile platform is a fully automatic unmanned robot or a remote control robot.

5. The time-lapse transient electromagnetic unmanned monitoring device for underground space according to claim 1, wherein, The planes where the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil are located are parallel to each other; both the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil are circular rings and have the same diameter.

6. A working method of the underground space time-lapse transient electromagnetic unmanned monitoring device according to any one of claims 1 to 5, characterized in that, The specific steps are as follows: Step 1. Determine the site model and survey line position planning: Before the detection operation starts, first use an unmanned device with a lidar scanner to scan the underground space comprehensively to construct a three-dimensional model of the underground space, and based on this model, plan the survey lines and the positions of each measuring point on the survey lines; Step 2. Equipment debugging and calibration: Before entering the underground space, first debug and calibrate the 8-shaped coil during shallow detection. In the state of the 8-shaped coil, manually control the transient electromagnetic receiving coil to fine-tune relative to the transient electromagnetic transmitting coil to the theoretical mutual inductance cancellation state and collect signals, and use this signal as the reference signal; After entering the underground space, the ground remote control terminal sends commands, and the control center controls the electric telescopic rod to horizontally move the transient electromagnetic receiving coil. During this process, the transient electromagnetic host controls the transient electromagnetic transmitting coil to emit electromagnetic signals, acquires the electromagnetic data received by the transient electromagnetic receiving coil for testing and detection, and compares the detection results with the reference signal and continuously corrects the position of the transient electromagnetic receiving coil until the error from the reference signal is less than the preset threshold, and maintains the current position of the transient electromagnetic receiving coil; Step 3. Conduct shallow detection operations: The mobile platform starts detection according to the survey line and the positions of each measuring point on the survey line planned in Step 1, and initially keeps the plane where the transient electromagnetic transmitting coil is located parallel to the ground. When the mobile platform reaches the first measuring point, it stops. The transient electromagnetic host conducts a primary detection of the floor of the underground space through the figure-eight coil. Subsequently, the control center controls the rotating motor to rotate the figure-eight coil by 90° until it is perpendicular to the ground, and the transient electromagnetic host conducts a primary detection of the side wall or side of the underground space; after completion, the mobile platform moves to the next measuring point, and the figure-eight coil is restored to its initial state during the movement; the detection process of the first measuring point is repeated for each subsequent measuring point until the shallow detection work of all measuring points is completed, and the control center transmits data to the ground remote control terminal; Step 4. Coil form switching: After receiving the data of the shallow detection, the ground remote control terminal sends commands. After receiving the commands, the control center controls the electric telescopic rod to extend and retract, thereby switching the transient electromagnetic transmitting coil and the transient electromagnetic receiving coil to an overlapping loop and maintaining it; Step 5. Conduct deep detection operations: The mobile platform returns along the original route according to the survey line and the positions of each measuring point on the survey line planned in Step 1 for deep detection, and initially keeps the plane where the transient electromagnetic transmitting coil is located parallel to the ground. When the mobile platform reaches the first measuring point, it stops. The transient electromagnetic host conducts a primary detection of the floor of the underground space through the overlapping loop. Subsequently, the control center controls the rotating motor to rotate the overlapping loop by 90° until it is perpendicular to the ground, and the transient electromagnetic host conducts a primary detection of the side wall or side of the underground space; after completion, the mobile platform moves to the next measuring point, and the overlapping loop is restored to its initial state during the movement; the detection process of the first measuring point is repeated for each subsequent measuring point until the deep detection work of all measuring points is completed, and the control center transmits data to the ground remote control terminal; Step 6. Data fusion processing: The ground remote control terminal separately conducts data fusion processing on the shallow data and deep data obtained from each measuring point, and generates a apparent resistivity map of the underground space based on the results of the data fusion; Step 7. Time-lapse transient electromagnetic method monitoring: Set the detection interval according to the actual situation and conduct periodic detection operations; the survey line and measuring points for each detection operation remain unchanged, and Steps 2 to 6 are repeated; after each periodic detection is completed, use the time-lapse algorithm of the transient electromagnetic method to calculate the data obtained from detections in different periods, which is used to infer the physical property evolution of abnormal bodies around the underground space on different time scales.

7. The working method according to claim 6, characterized in that, In the sixth step, the data fusion process refers to performing time-depth conversion on the data of shallow detection and deep detection at each measurement point of the same survey line through the smoke ring inversion theory, and then extracting the shallow [0’D1) data of the shallow detection data set and the deep [D1’D2] data of the deep detection data set, and recombining these two parts of data according to the principle of one-to-one correspondence of the same measurement points on the same survey line to obtain the [0’D2] data as the final data set of this survey line; where D1 and D2 respectively represent the depth of shallow detection and the depth of deep detection, and D2 is greater than D1.

8. The working method according to claim 7, characterized in that In the seventh step, the transient electromagnetic time-lapse algorithm is used to calculate the data obtained from detections with different periods, specifically: Assume that for the same measuring points in the underground space at different cycle times \(t_1\), \(t_2\), …, \(t\) n n detections are carried out, and the forward equation for each detection is expressed as: Among them, is the electrical model parameter of the underground space at time t, i and is the observation data at time t, and f is the transient electromagnetic forward operator; i ​ Through the inversion algorithm, the resistivity distribution at each moment is obtained: Taking the initial moment t1 as the reference benchmark, the resistivity change rate at the subsequent moment t i is: Through computational analysis The trend of change can be used to identify the dynamic change characteristics of abnormal underground media.

Images