Dam leakage detection method based on combination of circuit and electromagnetic field

Abstract

The invention discloses a dam leakage detection method based on combination of a circuit and an electromagnetic field. The method comprises the following steps: step 1, placing an emission electrode at a certain depth in a water area on one side of an upstream face of a dam; 2, a loop electrode is placed at the position 3 meters away from one side of the downstream face of the dam; step 3, connecting the emission electrode and the loop electrode by using a power supply to form a planar array; 4, detecting a voltage signal of the electromagnetic wave by the collecting electrode; step 5, placing a horizontally polarized loop antenna on one side for transmitting, and symmetrically placing a vertically polarized loop antenna and a line antenna on the other side for receiving; and 6, detecting the vertical position of the leakage path by using a common depth method. According to the detection method disclosed by the invention, the detection efficiency and precision can be improved, weak leakage can be accurately positioned, the operation is simple, operation by using a ship in water is not needed, and a dam structure does not need to be damaged by drilling.

Description

Technical Field

[0001] The present invention belongs to the technical field of dam leakage hidden danger detection, and in particular relates to a method for rapid and accurate positioning and detection of dam leakage in this field. Background Art

[0002] A method for quickly locating the leakage entrance of a dam based on electric field response (CN202311078714.X) uses the changes in the electric field received by a ship in the water to detect the leakage entrance. It cannot locate the leakage path in the dam, and the work efficiency is greatly affected by the ship.

[0003] The method of combining tomography and tracer methods to accurately locate leakage channels of dams under complex conditions (CN202310678027.5) requires drilling several exploration wells on the dam and performing three-dimensional inversion imaging of the detection data, which causes destructive damage to the dam, has low work efficiency and complex data processing.

[0004] The detection method and equipment for dam leakage (CN202211394081.9) transmits at different depths in the water and receives at the leakage outlet on the other side of the dam to form three-dimensional acquisition data for inversion imaging, which can locate the leakage path and depth. However, the amount of data required for three-dimensional inversion is large, the acquisition time is long, and the three-dimensional inversion processing time is as long as more than one week.

[0005] A miniaturized three-component anti-crosstalk magnetic core induction coil sensor and leakage detection method (CN202310079727.2) and a dam leakage path detection method (CN202211080472.3) are to insert electrodes at the downstream leakage outlet of a known dam. The seepage points of many dams are very small and the outlet location cannot be determined.

[0006] A method for detecting dam leakage by combining high-density electrical method and comprehensive tracer method (CN202210196807.1) uses high-density electrical method to detect the dam body. It is necessary to insert electrodes into the dam body. The detection process is cumbersome and cannot detect small seepage points. The tracer method also requires drilling, which is not very practical. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a dam leakage detection method based on the combination of circuit and electromagnetic field, which can quickly and non-destructively and accurately locate the leakage position on the dam surface, with a positioning depth of more than 50m. It is easy to operate and does not require ships, vehicles, or drilling.

[0008] The present invention adopts the following technical solution: A dam leakage detection method based on a combination of circuit and electromagnetic field, the improvement of which is that it includes the following steps: Step 1, placing the transmitting electrode at a certain depth in the water area on the water-facing side of the dam; Step 2, placing the return electrode 3 meters away from the back water side of the dam; Step 3, connecting the transmitting electrode and the return electrode with a power supply, and evenly placing the collecting electrodes at equal intervals on the upper surface or the back surface of the dam to form a planar array; Step 4: The electromagnetic wave emitted by the transmitting electrode will pass through the leakage point of the dam, and the voltage signal of the electromagnetic wave will be detected by the collecting electrode. The maximum value of the voltage signal is the horizontal position of the leakage point; Step 5: With the point at the horizontal position on the ground as the center point, place a horizontally polarized loop antenna on one side for transmission, and symmetrically place a vertically polarized loop antenna and a wire antenna on the other side for reception; Step 6: Detect the vertical position of the leakage path using the common depth method: Move the transmitter and receiver once every 0.5 meters to make the transmitter and receiver symmetrical around the center point, and obtain the measured voltage Vi, i=1, 2, ..., N. At the same time, the distance between the transmitter and the receiver is Ri, i=1, 2, ..., N. When Vi is the largest, according to the principle of the shortest radio wave propagation path, the distance Ri between the transmitter and the receiver is the vertical position of the leakage path; Step 7: Form three-dimensional precise positioning of the dam leakage entrance, path and exit.

[0009] Furthermore, in step 1, the depth is required to be half of the height of the dam. If the water surface height is lower than half of the height of the dam, the transmitting electrode is placed at half of the water depth.

[0010] The beneficial effects of the present invention are: The detection method disclosed in the present invention can improve detection efficiency and accuracy, accurately locate weak leakage, and is simple to operate. It does not require the use of boats in the water, nor does it require drilling holes to damage the dam structure. It does not require knowing the outlet and inlet of the leakage, and does not require subsequent complex and time-consuming inversion processing. The processing results can directly accurately locate and display the leakage path. The biggest advantage is that it has been verified by internal confidentiality experiments and is also applicable to dam structures containing metal objects such as steel bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the process of the detection method disclosed in the present invention; Figure 2 It is a schematic diagram of the placement of the transmitting electrode when the water level is halfway above the dam; Figure 3 This is a schematic diagram of the placement of the transmitting electrode when the water level is lower than half of the dam; Figure 4 It is a schematic diagram of the placement of the collection electrodes; Figure 5This is a schematic diagram of detecting the vertical position of the leakage path using the common depth method; Figure 6 is a schematic diagram of the simulated leakage test site; Figure 7 This is a picture of the experimental site; Figure 8 It is the experimental model diagram; Fig. 9 It is the distribution diagram of equipotential lines when there is leakage and when there is no leakage; Fig.10 This is the distribution diagram of equipotential lines after one week of continuous leakage; Fig.11 It is the graph of the change of the potential at the leak point with the leakage time; Fig.12 This is a picture of the on-site experiment with a steel mesh; Fig.13 It is the equipotential line distribution diagram with and without leakage when there is steel mesh; Fig.14 It is a schematic diagram of depth positioning. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0013] Example 1. This example discloses a dam leakage detection method based on a combination of circuits and electromagnetic fields. Based on the principle that water flows in a leakage path as a long conductor, an alternating current forms a voltage loop, and a collection electrode collects voltage values ​​on the surface of the dam to quickly determine the horizontal position of the leakage point. Then, on the surface of the dam, with the horizontal position of the leakage point as the center, a horizontally polarized loop antenna is placed on one side as a transmitter to form a long conductor electromagnetic field in the leakage path, and a vertically polarized loop antenna and a wire antenna are symmetrically placed on the other side as receivers to receive electromagnetic field signals. The vertical position of the leakage path is detected using the common depth method to form a three-dimensional precise positioning of the dam leakage entrance, path, and exit, such as Figure 1 As shown, the specific steps include: Step 1, placing the transmitting electrode at a certain depth in the water area on the water-facing side of the dam; like Figure 2 As shown, the depth requirement is optimal at half the height of the dam, as Figure 3 As shown, if the water surface height is lower than half of the dam height, the transmitting electrode is placed at half the water depth.

[0014] Step 2, placing the return electrode 3 meters away from the back water side of the dam; Step 3: Use a power supply to connect the transmitting electrode and the return electrode, and place the collecting electrodes evenly spaced on the upper surface of the dam or the back surface of the water to form a Figure 4 The planar array shown; Step 4: The electromagnetic wave emitted by the transmitting electrode will pass through the leakage point of the dam, and the voltage signal of the electromagnetic wave will be detected by the collecting electrode. The maximum value of the voltage signal is the horizontal position of the leakage point; Step 5: With the point at the horizontal position on the ground as the center point, place a horizontally polarized loop antenna on one side for transmission, and symmetrically place a vertically polarized loop antenna and a wire antenna on the other side for reception; Step 6, such as Figure 5 As shown, the vertical position of the leakage path is detected by the common depth method: Move the transmitter and receiver once every 0.5 meters to make the transmitter and receiver symmetrical around the center point, and obtain the measured voltage Vi, i=1, 2, ..., N. At the same time, the distance between the transmitter and the receiver is Ri, i=1, 2, ..., N. When Vi is the largest, according to the principle of the shortest radio wave propagation path, the distance Ri between the transmitter and the receiver is the vertical position of the leakage path; Step 7: Form three-dimensional precise positioning of the dam leakage entrance, path and exit.

[0015] According to the above technical solution, the following Figure 6 The simulated leakage test site shown in the figure has holes opened on the north and east walls of the pool, and the leakage pipes are pre-buried, with 200mm exposed. A cement layer is applied to the inner wall and bottom of the pool, and waterproof coating is applied to ensure waterproofing and no leakage. Earth is filled inside the pool, and the transmitting electrode tube is pre-buried in the earth to ensure the position and exposed length of the transmitting electrode.

[0016] The experimental site Figure 7 As shown in Figure 8 As shown. The monitoring wall is 2.5m high and 3.5*0.3*2.5m in size. The part buried in the stratum is 1.3m high. The detection area is within 3m to the north of the monitoring wall. Electrode B (-I), grounding electrode and measuring electrode are placed on the north side of the monitoring wall. Electrode A (+I) is placed in the well on the south side of the monitoring wall, 1m away from the monitoring wall and 2m away from the north and south walls on the west side. The leakage point is preset at 1.5m from the top of the wall and 1m away from the north and south walls on the west side. The wall to be tested is divided into two types: with or without steel mesh. The specific experiments are as follows.

[0017] (1) The wall to be tested has no steel mesh: First, measure the background field without water leakage, then add water to the experimental model to ensure that water seeps into the leaks, and then measure the potential at each point. The voltage applied during the measurement is 16mv. The measurement results are as follows Fig. 9 As shown. Fig. 9From the data of leakage, we can see that: when there is leakage, the potential near the wall is as high as 600mv, which is significantly stronger than the 160mv when there is no leakage, indicating that more current flows back to the B electrode to form a loop; the high potential domain of the equipotential coil in the no leakage diagram is at 2m, which is the location of electrode A, which is consistent with the theoretical and simulation results; the high potential domain of the equipotential coil in the leakage diagram is at 1m, which clearly and correctly delineates the location of the leakage point. After one week of continuous leakage, the measurement was repeated, and the results are as follows Fig.10 As shown, the leak point can still be accurately located, and due to the increase in formation moisture, the resistivity decreases, making the potential much higher than before. Fig.11 As the number of days of leakage increases, the potential at the leak (i.e., x=1m) changes. The horizontal axis is the number of days of leakage, and the vertical axis is the potential at the leak. Fig.11 It can be seen that when the leakage days are 0, that is, when there is no leakage, the potential at the leak is 159.6mv; when there is leakage for one day, the potential at the leak is 662.1mv; when there is leakage for 7 days, the potential at the leak is 2233mv; that is, as the leakage time increases, the potential at the leak also gradually increases. It is confirmed that the leakage measurement method of the present invention is real and feasible.

[0018] (2) The wall to be tested has a steel mesh: In order to explore whether the presence of steel bars will affect the location of the leak, such as Fig.12 As shown in the figure, 12mm steel bars are tied into a steel mesh with an interval of 0.2m and attached to the outside of the wall to simulate the reinforced concrete structure. The measurement is carried out after the landfill. The potential is still measured first when there is no leakage, and then when there is leakage. The measurement results are as follows Fig.13 As shown, the leakage point at 1m can still be located more accurately. Compared with the potential distribution diagram without steel mesh, it can be seen that the potential distribution near the wall is more uniform after the steel mesh is installed, and in the potential distribution diagram with steel mesh and no leakage, due to the more uniform potential distribution, there is almost no influence of the source. Therefore, in the presence of steel bars, the detection and positioning of the leakage point by the method of the present invention is not affected.

[0019] Finally, the depth is located by using the common depth method. The results are as follows: Fig.14 As shown, it can be seen that the center of the leakage point is 1.5m, which is Figure 6 The burial depths shown are the same.

[0020] In summary, the method of the present invention can accurately detect the leakage position in the case where the wall has or does not have steel bars.

Claims

1. A dam leakage detection method based on the combination of circuit and electromagnetic field, characterized in that: The steps include: Step 1, placing the transmitting electrode at a certain depth in the water area on the water-facing side of the dam; Step 2, placing the return electrode at a position 3 meters away from the back water side of the dam; Step 3, connecting the transmitting electrode and the return electrode with a power supply, and evenly placing the collecting electrodes at equal intervals on the upper surface or the back surface of the dam to form a planar array; Step 4: The electromagnetic wave emitted by the transmitting electrode will pass through the leakage point of the dam, and the voltage signal of the electromagnetic wave will be detected by the collecting electrode. The maximum value of the voltage signal is the horizontal position of the leakage point; Step 5: With the point at the horizontal position on the ground as the center point, place a horizontally polarized loop antenna on one side for transmission, and symmetrically place a vertically polarized loop antenna and a wire antenna on the other side for reception; Step 6: Detect the vertical position of the leakage path using the common depth method: Move the transmitter and receiver once every 0.5 meters to make the transmitter and receiver symmetrical around the center point, and obtain the measured voltage Vi, i=1, 2, ..., N. At the same time, the distance between the transmitter and the receiver is Ri, i=1, 2, ..., N. When Vi is the largest, according to the principle of the shortest radio wave propagation path, the distance Ri between the transmitter and the receiver is the vertical position of the leakage path; Step 7: Form three-dimensional precise positioning of the dam leakage entrance, path and exit.

2. The dam leakage detection method based on the combination of circuit and electromagnetic field according to claim 1 is characterized in that: In step 1, the depth is required to be half of the height of the dam. If the water surface height is lower than half of the height of the dam, the transmitting electrode is placed at half the water depth.

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