CN111239242B - Dam leakage channel detection method and device based on magnetic field measurement - Google Patents

Dam leakage channel detection method and device based on magnetic field measurement Download PDF

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CN111239242B
CN111239242B CN202010099289.2A CN202010099289A CN111239242B CN 111239242 B CN111239242 B CN 111239242B CN 202010099289 A CN202010099289 A CN 202010099289A CN 111239242 B CN111239242 B CN 111239242B
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CN111239242A (en
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汤井田
胡双贵
汤子键
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Central South University
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Abstract

The invention discloses a dam leakage channel detection method and a device thereof based on magnetic field measurement, wherein the method comprises the following steps: s1: acquiring a background magnetic induction vector on each magnetic observation point on a dam when a signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point when the signal transmitter is powered; arranging emission electrodes A and B on two sides of a dam, wherein the emission electrodes A are positioned in a reservoir and are in contact with water, a signal transmitter is connected between the emission electrodes A and B, and magnetic observation points are arranged on the dam according to a preset line distance and a preset point distance; s2: respectively calculating the difference value of the total magnetic induction vector and the background magnetic induction vector on each magnetic observation point to obtain the magnetic anomaly vector of each magnetic observation point; s3: and deducing current density distribution based on the magnetic anomaly vector of each magnetic observation point in the magnetic anomaly field, wherein the position where the current density distribution is not zero is a leakage channel. The invention provides a brand new method for realizing leakage channel detection, and magnetic detection is used for the first time.

Description

Dam leakage channel detection method and device based on magnetic field measurement
Technical Field
The invention belongs to the technical field of exploration geophysics, and particularly relates to a dam leakage channel detection method and a dam leakage channel detection device based on magnetic field measurement.
Background
China is a country with a lot of flood disasters, and losses caused by flood disasters are very large. Since the dam break or levee is an important cause of flood disasters, the dam leakage is a direct cause of the dam break or levee breach. In the last 90 th century, the university of the middle and south developed a dam piping leakage detector based on the flow field law theory first, and produced shaped products for popularization and application, which achieved good results. The current dam piping leakage instrument establishes an alternating current electric field between a leakage channel outlet and a water area in front of a dam, and determines the position of a dam leakage inlet by using the position of the singularity increased local current density or electric field strength. The existing methods are to measure the current density or electric field intensity in water to find the position of the dam leakage inlet, and besides determining the position of the leakage inlet, how to determine the leakage channel is an important aspect of dam detection. However, no people have adopted a magnetic field measurement method to determine the position of the dam piping channel so far, and the magnetic field measurement is rapid, convenient to operate and low in cost, so that the magnetic field measurement is very significant for determining the dam leakage channel, a means can be provided for rapid detection of the dam leakage channel, and the method is worthy of further intensive research.
Disclosure of Invention
The invention aims to provide a dam leakage channel detection method and a dam leakage channel detection device based on magnetic field measurement, which are used for determining the position of a dam piping channel by using the magnetic field measurement method for the first time, provide a brand new detection method, efficiently position the inner leakage channel of a dam and provide a technical means for dam protection and monitoring.
On one hand, the invention provides a dam leakage channel detection method and a dam leakage channel detection device based on magnetic field measurement, which comprises the following steps:
s1: acquiring a background magnetic induction vector on each magnetic observation point on a dam when a signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point when the signal transmitter is powered;
emitting electrodes A and B are arranged on two sides of a dam, the emitting electrodes A are located in a reservoir and are in contact with water, a signal transmitter is connected between the emitting electrodes A and B, and magnetic observation points are arranged on the dam according to a preset line distance and a preset point distance;
s2: respectively calculating the difference value of the total magnetic induction vector and the background magnetic induction vector on each magnetic observation point to obtain the magnetic anomaly vector of each magnetic observation point;
the magnetic anomaly vector based on each magnetic observation point forms a magnetic anomaly field of the dam;
S3: deducing current density distribution based on the magnetic anomaly vector of each magnetic observation point in the magnetic anomaly field;
wherein, the position where the current density distribution is not zero corresponds to the position of a leakage channel on the dam.
When a current signal is injected through the emitter electrodes a and B, and the current is guided along the preferential conductive path generated by the dam leakage path, the magnetic anomaly is generated by the current in the leakage path, and thus, the position of the leakage path on the dam is determined by the magnetic anomaly. It will be understood that the leakage pathway is formed by the water flow, and the conductivity of the water flow pathway is obviously higher than the background (non-water substances such as rock, clay or cement), therefore, the conductive current pathway can be associated with the water flow pathway of the dam leakage pathway, and the conductive current pathway can be determined by the magnetic field distribution. And the invention also verifies the gradient sensitivity of the magnetic induction intensity vector to the conductivity through formula reasoning, so that the characteristic of the flow field generated by the charge flow in the dam leakage channel is greatly reduced relative to the conductivity of the surrounding uniform material, and can be detected through magnetic measurement.
Therefore, according to the invention, the magnetic anomaly vector is obtained by firstly obtaining the background magnetic induction vector and the total magnetic induction vector obtained after current signals are injected through the A, B electrode, and then the current density distribution is obtained based on the magnetic anomaly vector, namely at the position of the leakage channel, the current density distribution obtained based on the magnetic anomaly vector is not zero, namely the current density distribution generated by retraction of the leakage channel can be obtained. At the position of the non-leakage channel (background of non-aqueous substances such as rocks, clay or cement), the current density distribution obtained based on the magnetic anomaly vector is zero. It should be understood that the current density distribution obtained by the present invention does not refer to the current density distribution of the total magnetic anomaly vector on the dam, but is directed to the current density distribution generated by the magnetic anomaly vector on the dam.
More preferably, step S3 is to estimate the current density distribution based on the relationship between the magnetic anomalous field and the current density field;
the dam is discretized into M units in three-dimensional space, each unit has the same volume, constant current density exists in each unit, and the relationship between the magnetic abnormal field and the current density field is as follows:
Bs＝KJ
Figure GDA0003245742520000021
in the formula, BsAs magnetic anomalous field momentsAn array, the size of which is 3 Nx 1,
Figure GDA0003245742520000022
respectively are magnetic abnormal vectors on the 1 st magnetic observation point and the Nth magnetic observation point, and N is the number of the magnetic observation points; k is a position matrix, the size of the matrix is 3 Nx 3M,
Figure GDA0003245742520000023
respectively are distance matrixes between the 1 st magnetic observation point and the 1 st unit and the Mth unit,
Figure GDA0003245742520000024
distance matrixes between the Nth magnetic observation point and the 1 st unit and the Mth unit are respectively set; j is a current density field matrix with a size of 3 Mx 1, J1、JMCurrent densities on the 1 st cell and the Mth cell, respectively;
wherein the magnetic anomaly vector of any ith magnetic observation point
Figure GDA0003245742520000025
Distance matrix between ith magnetic observation point and kth unit
Figure GDA0003245742520000026
Current density J on the kth cellkAs follows:
Figure GDA0003245742520000031
Figure GDA0003245742520000032
in the formula (I), the compound is shown in the specification,
Figure GDA0003245742520000033
are respectively magnetic anomaly vectors
Figure GDA0003245742520000034
In the skyThe components in the directions of x, y and z in an inter-rectangular coordinate system xyz, mu is the magnetic conductivity of the free space, ν is the unit volume, r ikIs the spatial distance between the ith magnetic observation point and the kth cell,
Figure GDA0003245742520000035
respectively the spatial distance between the ith magnetic observation point and the kth unit
Figure GDA0003245742520000036
Components in x, y, z directions in a spatial rectangular coordinate system xyz;
Figure GDA0003245742520000037
respectively the current density J on the k-th cellkThe components in the x, y, z directions in the spatial rectangular coordinate system xyz.
Further preferably, in step S3, the current density distribution is estimated by using a characteristic point method, a tangent method, a two-dimensional inversion method, or a linear three-dimensional inversion method of a magnetic anomaly curve based on the relationship between the magnetic anomaly field and the current density field.
Various algorithms are adopted to solve the current density distribution based on the relationship between the magnetic anomaly field and the current density field, wherein the inversion method also comprises but is not limited to a gauss-newton method, a nonlinear conjugate gradient method and a genetic algorithm.
Further preferably, the process of estimating the current density distribution by using the linear three-dimensional inversion method is as follows:
firstly, establishing an objective function phi (J) according to a least-squares algorithm principle and obtaining a solution of a linear inverse problem of the objective function;
wherein the objective function is as follows:
Φ(J)＝[Wd(dobs-KJ)]T[Wd(dobs-KJ)]+λ[Wm(J-J0)]T[Wm(J-J0)]
the formula of the solution is as follows:
Figure GDA0003245742520000038
wherein λ is a regularization factor, J0As a prior model of current density, d obsTo observe the data, wd、wmAre all weight matrices, weight matrix wdFor observation data dobsA diagonal matrix composed of the inverses of the error covariance matrix of (a), a weight matrix wmIs a smoothness matrix, also called weight coefficient matrix, usually taking an identity matrix Im；
Then substituting the magnetic abnormal field matrix and the position matrix on the dam into a formula of a solution to calculate a current density field matrix to obtain current density distribution on the dam;
wherein the magnetic anomalous field matrix Bs(3N×1)For observation data dobs. Further preferably, the magnetic induction vector is collected at the observation point by a magnetic probe.
On the other hand, the device based on the method provided by the invention comprises the following steps: the device comprises transmitting electrodes A and B, a signal transmitter, a receiver and an analysis processor;
the emitting electrodes A and B are respectively arranged on two sides of the dam, the emitting electrodes A are positioned in the reservoir and are in contact with water, and the signal transmitter is connected between the emitting electrodes A and B; arranging magnetic observation points on the dam according to a preset line distance and a preset point distance, wherein the receiver is arranged at the magnetic observation points to collect magnetic induction intensity vectors;
the analysis processor is connected with the receiver and used for acquiring a background magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is powered and identifying the position of a leakage channel on the dam.
Further preferably, the receiver is a magnetic probe or magnetometer.
Wherein, when the receiver is a magnetic probe, the receiver does not need to be grounded, thereby overcoming the difficulty of poor grounding condition of the dam.
Further preferably, the transmitting electrode B is located on land.
Further preferably, the transmission signal of the signal transmitter is a direct current signal or an alternating current signal with the frequency of 0.1-380 Hz.
Advantageous effects
The invention provides the gradient sensitivity of the magnetic induction intensity vector to the conductivity through theoretical reasoning, so that the electrical conductivity of the flow field generated by the charge flow in the dam leakage channel is greatly reduced relative to the electrical conductivity of the surrounding uniform material, and the magnetic sensitivity can be detected through magnetic measurement. The emission electrodes A and B are arranged based on the discovery, magnetic anomaly vectors are obtained through magnetic induction intensity vectors on each observation point under the condition of injecting current signals and non-injecting current signals, and then current density distribution is determined according to the magnetic anomaly vectors, wherein the current density distribution which is not zero is regarded as being generated by a leakage channel on a dam. The invention further provides a brand-new method for determining the position of the dam leakage channel, the position of the leakage channel is positioned by adopting a magnetic field measurement mode for the first time, and the method has the advantages of rapidness, convenience in operation and low cost based on the magnetic field measurement, so that the dam leakage channel can be determined more quickly, efficiently and lowly.
Drawings
Fig. 1 is a schematic diagram of dam leakage channel detection based on magnetic field measurement according to the present invention. A, B is an emitting electrode, A is located in water at one side of the reservoir, B is located in water or underground at the other side of the dam; i (omega, t) is a supply current; the solid circle is a magnetic induction intensity vector magnetic observation point and is arranged on the dam.
Detailed Description
The present invention will be further described with reference to the following examples.
The invention obtains the gradient sensitivity of the magnetic induction intensity vector to the electric conductivity by reasoning the formula of the magnetic anomaly vector, and the reasoning process is as follows:
the invention involves injecting current between two electrodes (in the ground or borehole) and measuring the magnetic induction in three orthogonal directions.
The method involves maxwell's equations under quasi-static conditions (i.e., ignoring the time derivatives in the conservation equations) as follows:
▽×E＝0 (1)
▽·B＝0 (2)
▽×B＝μJc (3)
wherein E is the electric field strength, B ═ μ H, B is the magnetic induction vector (or called magnetic flux density); h is the magnetization field, μ is the permeability of free space, JcIs the conduction current density.
According to equation (1), the electric field can pass
Figure GDA0003245742520000051
From a scalar potential
Figure GDA0003245742520000052
And (6) exporting. Whereas in a medium with a current generator, the total current can be divided into two parts: with a current generator J sThe associated primary current (source current density) and the volume current due to the electric field in the volume, so the conduction current density is as follows Jc：
Figure GDA0003245742520000053
In the formula, JsRepresenting the source current density (also called primary current density) within the source region, σ E is the bulk current density outside the source region.
At observation point P (r) (magnetometer position), the magnetic induction vector can be decomposed into background field magnetic induction vector B0(r) and the magnetic induction vector B generated by the current in the leakage paths(r)：
B(r)＝B0(r)+Bs(r) (5)
Using the curl we can obtain using Biot and Savart's law:
Figure GDA0003245742520000054
Figure GDA0003245742520000055
wherein r represents the position of a magnetic observation point P (r) laid in advance on the dam, r' represents the position of an integration point around the source point M,
the present invention also has another magnetic induction because the wires are located on the ground and are used to connect the current electrodes a and B to the generator. Current control J in the inventionsThe source of (a) is known. Therefore, we can easily delete the background field to get the outlier: b iss(r)＝B(r)-B0(r)。
By using
Figure GDA0003245742520000061
And × E ═ 0 (based on the quasi-static limits discussed above), then equation (7) may be written as:
Figure GDA0003245742520000062
uniform underground (∑ (r) ═ 0), the magnetic field drops to the background field B0. From equation (8), we can see that the magnetic induction vector is sensitive to the gradient of the electrical conductivity. That is, the flow field generated by the flow of charge in the dyke leakage channel is characterized by a strong drop in conductivity relative to the surrounding homogeneous material, which can be detected by magnetic measurement.
For anomalous fields, we can write equation (7) as follows, based on the relationship between current density and electromagnetic field:
Figure GDA0003245742520000063
where J (r') ═ σ E is the current density in the leakage channel.
Based on the theoretical basis, the method comprises the steps of firstly obtaining the magnetic abnormal field, then obtaining the current density distribution in the leakage channel by using the magnetic abnormal field, and further determining the leakage channel on the dam. As shown in figure 1, power supply electrodes A and B are arranged on two sides of a dam, wherein the power supply electrode A is positioned in a reservoir and is directly contacted with water, and the power supply electrode B is positioned on the other side of the reservoir, can be in water or land and is connected to a signal transmitter; the observation points are arranged on the dam according to the designed line distance and point distance, the receiver is used for collecting the magnetic induction intensity vector of the observation points, and the receiver in the embodiment adopts a magnetic probe or a magnetometer to measure the magnetic induction intensity vector point by point.
The invention provides a dam leakage channel detection method and a dam leakage channel detection device based on magnetic field measurement, which comprises the following steps:
s1: acquiring a background magnetic induction vector on each magnetic observation point on a dam when a signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point when the signal transmitter is powered;
For example, the background magnetic induction vector at the ith magnetic observation point
Figure GDA0003245742520000064
And total magnetic induction vector Bi(r)。
S2: and respectively calculating the difference value of the total magnetic induction vector and the background magnetic induction vector on each magnetic observation point to obtain the magnetic anomaly vector of each magnetic observation point.
At the ith magnetic observation point
Figure GDA0003245742520000065
Is equal to the total magnetic induction vector Bi(r) vector of magnetic induction with background
Figure GDA0003245742520000066
The difference of (a). And constructing a magnetic abnormal field of the dam based on the magnetic abnormal vector of each magnetic observation point.
S3: deducing current density distribution based on the magnetic anomaly vector of each magnetic observation point in the magnetic anomaly field;
wherein, the position where the current density distribution is not zero corresponds to the position of a leakage channel on the dam. In this embodiment, a linear three-dimensional inversion method is used to estimate the current density distribution, and the process is as follows:
the dykes are discretized in three dimensions into M cells, assuming that each cell has the same volume v underground and that there is a constant current density in each cell
Figure GDA0003245742520000071
For a single cell k and a single observation point i, the magnitude of the magnetic field can be expressed as:
Figure GDA0003245742520000072
for N stations, the magnetic anomaly field is related to the current density field as follows:
Bs＝KJ (11)
Figure GDA0003245742520000073
Figure GDA0003245742520000074
in the formula, BsIs a matrix of magnetic anomalous fields, the matrix size being 3N x 1,
Figure GDA0003245742520000075
respectively are magnetic abnormal vectors on the 1 st, ith and Nth magnetic observation points, and N is the number of the magnetic observation points; k is a position matrix, the size of the matrix is 3 Nx 3M,
Figure GDA0003245742520000076
Respectively are distance matrixes between the 1 st magnetic observation point and the 1 st unit and the Mth unit,
Figure GDA0003245742520000077
respectively are distance matrixes between the Nth magnetic observation point and the 1 st unit and the Mth unit,
Figure GDA0003245742520000078
a distance matrix between the ith magnetic observation point and the kth unit; j is a current density field matrix with a size of 3 Mx 1, J1、Jk、JMCurrent densities on the 1 st, kth and mth cells, respectively;
in the formula (I), the compound is shown in the specification,
Figure GDA0003245742520000079
are respectively magnetic anomaly vectors
Figure GDA00032457425200000710
The components in the directions of x, y and z in the space rectangular coordinate system xyz, mu is the magnetic conductivity of the free space, v is the unit volume, rikIs the spatial distance between the ith magnetic observation point and the kth cell,
Figure GDA00032457425200000711
respectively the spatial distance between the ith magnetic observation point and the kth unit
Figure GDA00032457425200000712
Components in x, y, z directions in a spatial rectangular coordinate system xyz;
Figure GDA00032457425200000713
respectively the current density J on the k-th cellkThe components in the x, y, z directions in the spatial rectangular coordinate system xyz.
The invention obtains a magnetic abnormal field matrix B by monitoring the magnetic induction intensity vector at an observation pointsAnd the position matrix K is known, and then how to solve the current density field matrix is the next step, in the embodiment of the invention, the objective function phi (J) is established according to the principle of the least multiplication algorithm and the solution of the linear inverse problem of the objective function is obtained;
Wherein the objective function is as follows:
Φ(J)＝[Wd(dobs-KJ)]T[Wd(dobs-KJ)]+λ[Wm(J-J0)]T[Wm(J-J0)]
the formula of the solution is as follows:
Figure GDA0003245742520000081
wherein λ is a regularization factor, J0As a prior model of current density, dobsTo observe the data, wd、wmAre all weight matrices, weight matrix wdFor observation data dobsA diagonal matrix composed of the inverses of the error covariance matrix of (a), a weight matrix wmIs a smoothness matrix. The prior model is derived based on historical experimental data or historical data of current density distribution, leakage channels and magnetic abnormal fields in historical monitoring data.
Substituting the magnetic abnormal field matrix and the position matrix on the dam into a formula of a solution to calculate a current density field matrix to obtain the current density distribution on the dam, wherein the magnetic abnormal field matrix Bs(3N×1)For observation data dobs。
It should be noted that, in other possible embodiments, it is further preferable that, in step S3, based on the relationship between the magnetic anomaly field and the current density field, the current density distribution may also be derived by using a characteristic point method, a tangent method, and a two-dimensional inversion method of the magnetic anomaly curve, where the inversion method also includes, but is not limited to, a gauss-newton method, a nonlinear conjugate gradient method, and a genetic algorithm.
On the other hand, the device based on the method provided by the invention comprises the following steps: the device comprises transmitting electrodes A and B, a signal transmitter, a receiver and an analysis processor;
The emitting electrodes A and B are respectively arranged on two sides of the dam, the emitting electrodes A are positioned in the reservoir and are in contact with water, and the signal transmitter is connected between the emitting electrodes A and B; arranging magnetic observation points on the dam according to a preset line distance and a preset point distance, wherein the receiver is arranged at the magnetic observation points to collect magnetic induction intensity vectors;
and the analysis processor is connected with the receiver and is used for acquiring a background magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is powered, and identifying the position of a leakage channel on the dam. The analysis processor can be a computer or other terminal equipment containing a processing chip, stores a program corresponding to the method, and calls and runs the stored program to determine the position of the leakage channel.
Wherein the receiver is preferably a magnetic probe or magnetometer. The transmitting signal of the signal transmitter is a direct current signal or an alternating current signal with the frequency of 0.1-380 Hz.
It should be emphasized that the examples described herein are illustrative and not restrictive, and thus the invention is not to be limited to the examples described herein, but rather to other embodiments that may be devised by those skilled in the art based on the teachings herein, and that various modifications, alterations, and substitutions are possible without departing from the spirit and scope of the present invention.

Claims (8)

1. A dam leakage channel detection method based on magnetic field measurement is characterized in that: the method comprises the following steps:
s1: acquiring a background magnetic induction vector on each magnetic observation point on a dam when a signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point when the signal transmitter is powered;
emitting electrodes A and B are arranged on two sides of a dam, the emitting electrodes A are located in a reservoir and are in contact with water, a signal transmitter is connected between the emitting electrodes A and B, and magnetic observation points are arranged on the dam according to a preset line distance and a preset point distance;
s2: respectively calculating the difference value of the total magnetic induction vector and the background magnetic induction vector on each magnetic observation point to obtain the magnetic anomaly vector of each magnetic observation point;
the magnetic anomaly vector based on each magnetic observation point forms a magnetic anomaly field of the dam;
s3: deducing current density distribution based on the magnetic anomaly vector of each magnetic observation point in the magnetic anomaly field;
wherein, the position where the current density distribution is not zero corresponds to the position of a leakage channel on the dam;
step S3 is to deduce the current density distribution based on the relationship between the magnetic abnormal field and the current density field;
if the dam is discretized into M cells in three-dimensional space, each cell has the same volume and each cell has a constant current density, the relationship between the magnetic anomalous field and the current density field is as follows:
Bs＝KJ
Figure FDA0003258907540000011
In the formula, BsIs a matrix of magnetic anomalous fields, the matrix size being 3N x 1,
Figure FDA0003258907540000012
respectively are magnetic abnormal vectors on the 1 st magnetic observation point and the Nth magnetic observation point, and N is the number of the magnetic observation points; k is a position matrix, the size of the matrix is 3 Nx 3M,
Figure FDA0003258907540000013
respectively are distance matrixes between the 1 st magnetic observation point and the 1 st unit and the Mth unit,
Figure FDA0003258907540000014
distance matrixes between the Nth magnetic observation point and the 1 st unit and the Mth unit are respectively set; j is a current density field matrix with a size of 3 Mx 1, J1、JMThe current densities of the 1 st cell and the Mth cell, respectively.
2. The dam leakage pathway detection method of claim 1, wherein: in step S3, the current density distribution is estimated by using a characteristic point method, a tangent method, a two-dimensional inversion method, or a linear three-dimensional inversion method of the magnetic anomaly curve based on the relationship between the magnetic anomaly field and the current density field.
3. The dam leakage pathway detection method of claim 2, wherein: the process of estimating the current density distribution by adopting a linear three-dimensional inversion method is as follows:
firstly, establishing an objective function phi (J) according to a least-squares algorithm principle and obtaining a solution of a linear inverse problem of the objective function;
wherein the objective function is as follows:
Φ(J)＝[Wd(dobs-KJ)]T[Wd(dobs-KJ)]+λ[Wm(J-J0)]T[Wm(J-J0)]
The formula of the solution is as follows:
Figure FDA0003258907540000021
wherein λ is a regularization factor, J0As a prior model of current density, dobsTo observe the data, Wd、WmAre all weight matrices, weight matrix WdFor observation data dobsA diagonal matrix composed of the inverses of the error covariance matrix of (1), a weight matrix WmIs a smoothness matrix;
then substituting the magnetic abnormal field matrix and the position matrix on the dam into a formula of a solution to calculate a current density field matrix to obtain current density distribution on the dam;
wherein the magnetic anomalous field matrix Bs(3N×1)For observation data dobs。
4. The dam leakage pathway detection method of claim 1, wherein: and collecting the magnetic induction intensity vector by using a magnetic probe at an observation point.
5. An apparatus based on the dam leakage path detecting method according to any one of claims 1 to 4, wherein: the method comprises the following steps: the device comprises transmitting electrodes A and B, a signal transmitter, a receiver and an analysis processor;
the emitting electrodes A and B are respectively arranged on two sides of the dam, the emitting electrodes A are positioned in the reservoir and are in contact with water, and the signal transmitter is connected between the emitting electrodes A and B; arranging magnetic observation points on the dam according to a preset line distance and a preset point distance, wherein the receiver is arranged at the magnetic observation points to collect magnetic induction intensity vectors;
The analysis processor is connected with the receiver and used for acquiring a background magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is not powered and a total magnetic induction vector on each magnetic observation point acquired by the receiver when the signal transmitter is powered and identifying the position of a leakage channel on the dam.
6. The apparatus of claim 5, wherein: the receiver is a magnetic probe or a magnetometer.
7. The apparatus of claim 5, wherein: the transmitting electrode B is located on land.
8. The apparatus of claim 5, wherein: the transmitting signal of the signal transmitter is a direct current signal or an alternating current signal with the frequency of 0.1-380 Hz.
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