Dam leakage channel rapid positioning method based on total magnetic field gradient measurement

Abstract

The invention discloses a dam leakage channel rapid positioning method based on total magnetic field gradient measurement, and belongs to the technical field of water conservancy and engineering geophysical prospecting. The method comprises the following steps: arranging power supply electrodes and establishing a current loop; designing a gradient observation device, and observing a magnetic field component generated by the current channel by using the gradient observation device; an observation section is arranged in the direction perpendicular to the leakage channel, and three-component magnetic anomaly observation is conducted through a gradient observation device; calculating a total magnetic field abnormal value at different observation heights by using the observed three-component magnetic abnormal value, and calibrating the transverse position of the leakage channel; and calculating the longitudinal burial depth of the leakage channel based on the total magnetic field abnormal value of different observation heights corresponding to the transverse position of the leakage channel. According to the method, the characteristic that the total magnetic field intensity generated by the leakage channel under artificial source excitation is inversely proportional to the distance is utilized, the burial depth of the leakage channel is calculated, the leakage channel is positioned, the positioned leakage channel is combined with the leakage outlet of the downstream face, and the water inlet of the leakage channel is searched.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy and engineering geophysical exploration, and in particular to a method for quickly locating a leakage channel of a dam based on total magnetic field gradient measurement. Background Art

[0002] Some levees have been in operation for a long time, and there are many and complex hidden dangers. Leakage, piping, and even levee breaches have caused huge losses to people's lives and property. The location of the leakage channel is the key to preventing piping leakage and strengthening the levees. At present, the geophysical methods used for detecting piping leakage hazards mainly include seismic refraction wave method, resistivity method, transient electromagnetic, ground penetrating radar, natural electric field method and pseudo-flow field method. Among them, the pseudo-flow field method is a fast and efficient leakage entrance detection method proposed by He Jishan. Based on the similarity between the water flow field and the electric current field, this method establishes an artificial source current field to fit the leakage water flow field, and determines the flow direction and relative flow velocity of the water flow field by measuring the distribution of the current field. The traditional pseudo-flow field method mainly detects the electric field component, and the application scenario is in water, so it is necessary to keep the probe as close to the bottom of the water as possible. When the underwater environment is complex and the detection water area is deep, the probe is easily stuck and entangled by foreign objects, which doubles the construction difficulty. In addition, this method has accurate positioning of the leakage inlet, but it is difficult to reflect the changing trend and direction of the leakage channel.

[0003] Therefore, it is necessary to provide a method for quickly locating leakage channels of dams based on total magnetic field gradient measurement. Summary of the invention

[0004] The purpose of the present invention is to provide a method for quickly locating leakage channels of dams based on total magnetic field gradient measurement, so as to solve the problem that the pseudo-flow field method in the prior art can only locate the leakage entrance but is difficult to reflect the changing trend and direction of the leakage channel.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for quickly locating leakage channels of dams based on total magnetic field gradient measurement comprises the following steps:

[0007] Step S101: power supply electrodes are arranged at the outlet of the seepage channel on the back surface of the dam and at a certain distance away from the front surface of the dam, and current signals of different frequencies are given to establish a current loop, so that a current channel is formed in the seepage channel;

[0008] Step S102: designing a gradient observation device based on a magnetic sensor, wherein the observation height difference of the magnetic sensor is Δh, and using the gradient observation device to observe the magnetic field component generated by the current channel;

[0009] Step S103: Arrange an observation profile in the direction perpendicular to the leakage channel, and perform three-component magnetic anomaly observation using the gradient observation device;

[0010] Step S104: Calculate the total magnetic field anomaly values at different observation heights using the three-component magnetic anomaly values observed in Step S103, and calibrate the lateral position of the leakage channel based on the total magnetic field anomaly intensity;

[0011] Step S105: Calculate the longitudinal buried depth of the leakage channel based on the total magnetic field anomaly values at different observation heights corresponding to the lateral position of the leakage channel in Step S104, and calibrate the longitudinal position of the leakage channel;

[0012] Step S106: Integrate the lateral calibration position of the leakage channel in Step S104 and the longitudinal calibration position of the leakage channel in Step S105 to determine the inlet position of the leakage channel and achieve precise positioning of the leakage channel.

[0013] Furthermore, a rapid positioning method for dam leakage channels based on total magnetic field gradient measurement further includes: improving the data anti-interference ability and the positioning accuracy of the leakage channel by using simultaneous emission technology and reception technology.

[0014] Furthermore, the specific steps for calibrating the lateral position of the leakage channel are as follows:

[0015] Based on the spatial coordinates corresponding to the total magnetic field anomaly extreme values H max corresponding to different frequencies, calibrate the lateral position of the current channel;

[0016] The specific steps for calibrating the longitudinal position of the leakage channel are as follows:

[0017] Based on the total magnetic field intensity values H low and H high corresponding to the lateral position, calculate the longitudinal buried depth of the leakage channel. The calculation formula is as follows:

[0018]

[0019] In the formula: Δh is the longitudinal height difference between two magnetic sensors, h is the buried depth of the leakage channel, H high is the total magnetic field intensity measured at a higher position, and H low is the total magnetic field intensity measured at a lower position.

[0020] Furthermore, a rapid positioning method for dam leakage channels based on total magnetic field gradient measurement further includes: combining the lateral position and longitudinal position of the leakage channel with the leakage outlet to determine the leakage inlet.

[0021] The present invention has the following beneficial effects:

[0022] The present invention utilizes the characteristic that the total magnetic field intensity generated by a leakage channel under artificial source excitation is inversely proportional to the distance to calculate the burial depth of the leakage channel and locate the leakage channel. By combining the located leakage channel with the leakage outlet on the backwater side, the water inlet of the leakage channel is found, thus making up for the deficiency that the traditional pseudo-flow field method can only locate the leakage inlet and outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a rapid positioning method for a dam leakage channel based on total magnetic field gradient measurement in an embodiment of the present application;

[0024] Figure 2 It is a schematic structural diagram of a rapid positioning method for a dam leakage channel based on total magnetic field gradient measurement in an embodiment of the present application;

[0025] Figure 3 It is a schematic diagram of the spatial position relationship between a gradient observation device and a leakage channel in an embodiment of the present application;

[0026] Figure 4 It is a schematic diagram of a design model in an embodiment of the present application;

[0027] Figure 5 It is a graph of the total magnetic field intensity corresponding to different survey lines, which is the simulation result of a design model by finite element analysis software in an embodiment of the present application;

[0028] Figure 6 It is a schematic diagram of the calibration result of the lateral position of a pipeline corresponding to different survey lines, which is the simulation result of a design model by finite element analysis software in an embodiment of the present application;

[0029] Figure 7 It is a comparison graph of the calculated channel burial depth and the actual burial depth obtained by using this example at different burial depths in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Next, the specific embodiments in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0031] Based on the basic theory of the charging method, when there is a leakage channel in the dam, due to the water flow, there is a conductivity difference between the leakage channel and the surrounding rock. By arranging power supply electrodes on the backwater side and the upstream side of the dam respectively and applying current signals with different frequencies (the frequency is less than 1 kHz), the current will propagate along the dominant channel (leakage channel) with higher conductivity inside the dam, forming a current loop. According to the Biot-Savart law, the dominant current channel will generate a magnetic field in space. By arranging two three-component high-precision magnetic sensors with a height difference of Δh on the top of the dam to observe the total magnetic field anomaly generated by the dominant current channel, the lateral calibration position of the possible leakage path in the dam can be obtained. By using the lateral calibration position of the leakage path and Δh, the longitudinal calibration position of the channel can be calculated. Combining the spatial positioning of the leakage channel and the leakage outlet position, the position of the leakage inlet can be judged, so as to realize the rapid positioning of the leakage channel in the dam.

[0032] As Figure 1-7 shown, this embodiment provides a method for rapid positioning of dam leakage channels based on total magnetic field gradient measurement, including the following steps:

[0033] Step S101: Establish a uniform current field. Arrange power supply electrodes at the outlet position of the leakage channel on the backwater side of the dam and at a certain distance away from the upstream side of the dam respectively, and apply current signals with different frequencies to establish a current loop and form a dominant current channel in the leakage channel, as Figure 2 shown.

[0034] According to the Biot-Savart law, the magnetic induction intensity

[0035]

[0036] of the observation point P high is represented by H low for the magnetic sensor at the higher position and the magnetic field measured by the magnetic sensor at the lower position is represented by H Figure 3 as shown.

[0037] Step S102: Construct a gradient observation device. Design a gradient observation device based on high-precision magnetic sensors, with a height difference of Δh between the magnetic sensors. Use this gradient observation device to observe the magnetic field components generated by the dominant current channel, where the magnetic sensor at the higher position is represented by H Figure 4 as shown.

[0038] Step S104: Calculate the total magnetic field anomaly values at different observation heights based on the three-component magnetic anomaly values observed in Step S103, and calibrate the lateral position of the leakage channel based on the total magnetic field anomaly intensity. When the observation point is directly above the leakage pipeline, the total magnetic field intensity is the strongest, i.e., H max The corresponding position is the lateral calibration position of the possible leakage channel, such as Figure 5 shown.

[0039] Step S105: Calculate the longitudinal burial depth of the leakage channel based on the total magnetic field anomaly values at different observation heights corresponding to the lateral position of the leakage channel in Step S104, and realize the calibration of the longitudinal position of the leakage channel, such as Figure 6 shown.

[0040] When the observation point is directly above the leakage channel, the total magnetic field intensity observed is expressed as follows:

[0041]

[0042] where I0 is the current intensity flowing through the leakage channel, and h is the burial depth of the leakage channel. At this time, the magnetic field intensities at different observation heights are as follows:

[0043]

[0044] Solving the above equations can obtain the burial depth h of the leakage channel, and the expression is as follows:

[0045]

[0046] Step S106: Integrate the lateral calibration position of the leakage channel in Step S104 and the longitudinal calibration position of the leakage channel in Step S105 to realize the rapid and accurate positioning of the leakage channel, such as Figure 7 shown.

[0047] The present invention utilizes the characteristic that the total magnetic field intensity generated by the leakage channel under the excitation of the artificial source is inversely proportional to the distance, calculates the burial depth of the leakage channel, locates the leakage channel, and combines the located leakage channel with the leakage outlet on the backwater surface to find the water inlet of the leakage channel, making up for the deficiency that the traditional quasi-flow field method can only locate the leakage inlet and outlet.

[0048] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for quickly locating leakage channels of dams based on total magnetic field gradient measurement, characterized in that: The following steps are involved: Step S101: power supply electrodes are arranged at the outlet of the seepage channel on the back surface of the dam and at a certain distance away from the front surface of the dam, and current signals of different frequencies are given to establish a current loop, thereby forming a current channel in the seepage channel; Step S102: designing a gradient observation device based on a magnetic sensor, wherein the observation height difference of the magnetic sensor is Δh, and using the gradient observation device to observe the magnetic field component generated by the current channel; Step S103: Arranging an observation profile in a direction perpendicular to the leakage channel, and using the gradient observation device to perform three-component magnetic anomaly observation; Step S104: Calculate the total magnetic field anomaly values ​​at different observation heights using the three-component magnetic anomaly values ​​observed in step S103, and calibrate the lateral position of the leakage channel based on the total magnetic field anomaly intensity; Step S105: calculating the longitudinal burial depth of the leakage channel based on the total magnetic field anomaly values ​​at different observation heights corresponding to the lateral position of the leakage channel in step S104, and calibrating the longitudinal position of the leakage channel; Step S106: Combining the transverse calibrated position of the leakage channel in step S104 with the longitudinal calibrated position of the leakage channel in step S105, the water inlet position of the leakage channel is determined to achieve accurate positioning of the leakage channel.

2. The method for quickly locating leakage channels of dams based on total magnetic field gradient measurement according to claim 1 is characterized in that: Also includes: Simultaneous transmission technology and receiving technology are used to improve data anti-interference capabilities and the positioning accuracy of leakage channels.

3. The method for quickly locating leakage channels of dams based on total magnetic field gradient measurement according to claim 1 is characterized in that: The steps for calibrating the lateral position of the leakage channel are specifically as follows: According to the total magnetic field anomaly extreme value H corresponding to different frequencies max Corresponding spatial coordinates, marking the lateral position of the current channel; The longitudinal position calibration steps of the leakage channel are specifically as follows: According to the total magnetic field strength value H corresponding to the lateral position low and H high The longitudinal buried depth of the leakage channel is calculated using the following formula: Where: Δh is the longitudinal height difference between the two magnetic sensors, h is the buried depth of the leakage channel, H high is the total magnetic field strength measured at the higher position, H low is the total magnetic field strength measured at the lower position.

4. The method for quickly locating leakage channels of dams based on total magnetic field gradient measurement according to claim 3 is characterized in that: Also includes: The leakage inlet is determined by combining the lateral position and the longitudinal position of the leakage channel with the leakage outlet.

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