Method for detecting seepage of earth-rock dam based on combination of transient electromagnetic method and single-hole dilution method

Abstract

The present application mainly relates to the technical field of earth-rock dam leakage detection, and specifically relates to an earth-rock dam leakage detection method based on the combination of transient electromagnetic method and single-hole dilution method. The transient electromagnetic method is used to quickly scan and locate the leakage hidden trouble area, guide the single-hole dilution method to implement drilling in the key area, and reduce invalid drilling. On the basis of the traditional dilution curve model, a drilling radius correction factor and a non-Darcy effect correction term are introduced, which significantly improves the accuracy of the vertical seepage profile output. A quantitative mapping model of the resistivity inversion image and the seepage velocity is established to realize the quantitative conversion of physical detection data to hydraulic parameters. Based on the image recognition technology, the spatial distribution of the leakage channel is automatically extracted to realize the rapid calculation of the total amount of dam leakage.

Description

Technical Field

[0001] This invention mainly relates to the technical field of seepage detection in earth-rock dams, specifically a seepage detection method for earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method. Background Technology

[0002] Seepage in earth-rock dams is one of the key hidden dangers threatening dam safety, and rapid and accurate quantitative assessment of seepage is crucial for project safety. Traditional seepage detection methods have significant limitations:

[0003] Manual inspections, water level observations, and temperature field monitoring mainly focus on locating or qualitatively judging seepage points, making it difficult to accurately calculate the amount of seepage. While methods such as borehole pressure tests and water injection tests can obtain local seepage parameters, they are inefficient, have limited coverage, and are difficult to characterize the complex distribution of seepage channels inside the dam.

[0004] Existing single geophysical exploration techniques (such as transient electromagnetic methods) can quickly detect and invert to obtain dam resistivity profiles, effectively identifying low-resistivity anomalies to locate potential leakage areas. However, this method essentially provides the electrical characteristics of the medium and cannot be directly converted into leakage velocity or flow rate. While high-precision point measurement methods (such as single-hole dilution methods) can directly measure vertical seepage velocity in boreholes with accurate and reliable results, their data only represent information from a single point or a small local area. Furthermore, deploying a large number of boreholes is costly and inefficient, making it impossible to obtain the overall seepage field distribution of the dam body economically and efficiently. Summary of the Invention

[0005] To address the shortcomings of current technologies, this invention combines existing technologies and, based on practical applications, provides a method for detecting seepage in earth-rock dams that combines transient electromagnetic methods with single-hole dilution methods, enabling rapid detection of seepage in earth-rock dams.

[0006] The technical solution of the present invention is as follows:

[0007] A method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method includes the following steps:

[0008] S1. Obtain resistivity profile images based on transient electromagnetic method to locate potential leakage areas;

[0009] S2. Based on the leakage hazard area located by the transient electromagnetic method, determine the drilling location and depth, and calculate the seepage velocity based on the single-hole dilution method;

[0010] S3. Extract features from the resistivity profile image and establish a quantitative mapping relationship between the seepage velocity and the resistivity profile image to obtain the correlation model.

[0011] S4. Identify, segment, and extract the area of ​​the seepage hazard zone in the entire earth-rock dam profile. Based on the established seepage velocity-resistivity profile image association model, calculate the seepage volume of the entire dam profile.

[0012] Furthermore, in step S1, the transient electromagnetic method sends a pulsed magnetic field to the ground through a transmitting coil and measures the induced secondary field during the off period. The leakage hazard area has a low resistance characteristic due to its high water content, forming an abnormal area in the resistivity profile.

[0013] Furthermore, in step S2, when calculating the seepage velocity using the single-hole dilution method, a borehole radius correction factor is introduced. β Non-Darcy effect correction term c The revised formula for calculating the flow velocity is as follows:

[0014] v z修正 = β · c · πr / (2 α 1 t )·ln( C 0 / C t );

[0015] Among them, the borehole radius correction factor β The expression is as follows:

[0016] β =(1+ r / L ) n ;

[0017] Non-Darcy effect correction term c The expression is as follows:

[0018] c =1+ a 2· Re;

[0019] In the formula, v z修正 For depth Z Correction value for vertical seepage velocity at the location. C 0 For time t Conductivity at 0; C t For time t conductivity at that time; t For measuring time; r The radius of the borehole; α 1 For correction factors, L is included Characteristic length of water layern It is an experience index. a 2 is an empirical coefficient. Re It is the Reynolds number.

[0020] Furthermore, in step S3, the specific steps for extracting features from the resistivity profile image are as follows:

[0021] S311. Perform two-dimensional grayscale processing on the resistivity profile generated by the transient electromagnetic method inversion, converting the RGB image into a grayscale matrix, as shown in the following expression:

[0022] ;

[0023] In the formula, I gray ( X , Z ) is a resistivity profile image in coordinates ( X , Z The grayscale value of ) R、G、B These are the values ​​for the red, green, and blue channels, respectively. l r , l g , l b They are respectively R、G、B Corresponding coefficient value; X , Z For pixel coordinates, X In the horizontal direction, Z Vertical direction;

[0024] S312. The median filtering method is used to denoise the grayscale matrix. The expression is as follows:

[0025] ;

[0026] In the formula: k The radius of the filtering window; i The horizontal offset represents the step size of the filter window in the horizontal direction. j The vertical offset represents the step size of the filter window in the vertical direction.

[0027] S313. Leakage area segmentation: Otsu adaptive threshold segmentation based on grayscale values ​​is used to generate a binary mask, with the hidden danger area set to 1 and the normal area set to 0. The threshold segmentation expression is as follows:

[0028] ;

[0029] In the formula: T The threshold for segmenting the image, below T The pixels above are considered potential leakage areas. TPixels are considered normal areas; To be the optimal threshold, , They are respectively lower than T and higher T Pixel ratio; , They are respectively , The average grayscale value of these two types of pixels.

[0030] Furthermore, in step S3, the method for establishing the association model is as follows:

[0031] S321, Data pairing: The depth measured by the single-well dilution method... Z Vertical seepage velocity correction value at the location v z修正 With resistivity profile image in coordinates ( X , Z grayscale value I gray ( X , Z Accurately align at the same borehole location and depth to construct a modeling dataset;

[0032] S322, Spatial Positioning: Extract the vertical distribution curve of resistivity grayscale values ​​along the borehole axis. This curve is derived from the coordinate system (…). Xz , Z j grayscale value at ) I gray ( Xz , Z j )constitute, Xz Let be the coordinates of the borehole in the horizontal direction. Z j To establish coordinates at different borehole depths, the single-hole dilution method measures the seepage velocity at depth intervals within the same borehole. v zj修正 This forms a discrete dataset. v zj修正 , Z j};

[0033] S323, Depth Alignment: Alignment of grayscale values I gray ( Xz , Z j Cubic spline interpolation is used to match the sampling point depth of the single-well dilution method. The expression for the interpolated grayscale value is as follows:

[0034] I inter ( Xz ,Z j )=spline( I gray ( Xz , Z j ), Z j );

[0035] The paired dataset expression is as follows:

[0036] D={ I inter ( Xz , Z j ), v zj修正};

[0037] S324. Nonlinear Regression Modeling: Establishing Seepage Velocity v zj修正 With resistivity gray value I inter ( Xz , Z j A quantitative relationship model is used to reflect the low-resistance, high-velocity characteristics within the leakage channel. Weighted least squares method is employed for parameter fitting, and the objective function for fitting is:

[0038] ;

[0039] In the formula: w i The weight value is [value], and the weight value for the high-velocity region is [value]. w i =ln( v zj修正 +1); or 1 is a proportionality coefficient, reflecting the permeability of the medium; or 2 is the sensitivity index, which reflects the intensity of the flow velocity response to changes in resistivity.

[0040] Furthermore, the nonlinear regression modeling parameters are solved using the LM iterative method, with the algorithm's convergence condition being:

[0041] ;

[0042] In the formula: Δ or 1 is or The change in 1; Δ or 2 is or The change in 2.

[0043] The beneficial effects of this invention are:

[0044] This invention provides a rapid detection method for seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method. The transient electromagnetic method quickly scans and locates potential seepage areas, guiding the single-hole dilution method to drill in key areas and reduce ineffective drilling. Based on the traditional dilution curve model, a borehole radius correction factor and a non-Darcy effect correction term are introduced, significantly improving the accuracy of the vertical seepage profile output. A quantitative mapping model between resistivity inversion images and seepage velocity is established, realizing the quantitative conversion of physical detection data into hydraulic parameters. Based on image recognition technology, the spatial distribution of seepage channels is automatically extracted, enabling rapid calculation of the total dam seepage. Attached Figure Description

[0045] Figure 1 This is a flowchart of the present invention;

[0046] Figure 2 A schematic diagram of the abnormal zone of potential dam leakage hazards obtained by transient electromagnetic method inversion;

[0047] Figure 3 A schematic diagram for determining borehole locations based on anomaly zones;

[0048] Figure 4 This is a schematic diagram of the grayscale values ​​of the resistivity profile.

[0049] Figure 5 A schematic diagram for identifying, segmenting, and extracting all leakage areas in the inversion profile. Detailed Implementation

[0050] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0051] This embodiment provides a method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method. The specific method is as follows:

[0052] (I) Detection of seepage hazard zones in earth-rock dams based on transient electromagnetic method

[0053] Transient electromagnetic method (TEM) transmits pulsed magnetic fields into the ground via a transmitting coil and measures the induced secondary field during the off-period. Leakage zones, due to their high water content, exhibit low resistivity, forming anomalous areas in resistivity profiles, such as... Figure 2 As shown.

[0054] (II) Leakage velocity measurement based on single-hole dilution method

[0055] Based on the transient electromagnetic method, the leakage anomaly zone (leakage hazard zone) is obtained through inversion, and the horizontal position and depth of the borehole are determined, such as... Figure 3 As shown.

[0056] Currently, seepage velocity is often calculated based on the dilution curve (conductivity-time decay model), as shown in formula (1). However, this formula does not consider the influence of the borehole itself on the water flow velocity field, resulting in distortion of the velocity measurement value.

[0057] v = πr 2 / (2 α 1 t )·ln( C 0 / C t (1)

[0058] In the formula: C 0 For time t Conductivity at 0; C t For time t conductivity at that time; t For measuring time; r The radius of the borehole; α 1 is the correction factor (generally taken as 1~2).

[0059] To reduce the deviation in velocity estimation caused by the inherent geometric effects of boreholes (local velocity amplification) and non-Darcy flow (inertial effect), a borehole radius correction factor is introduced based on formula (1). β Non-Darcy effect correction term c A revised flow velocity formula was established.

[0060] Drill radius correction factor β This factor is related to the borehole radius. r Characteristic length of aquifer L Regarding the correction of local flow field distortion caused by drilling, expression (2) is as follows:

[0061] β =(1+ r / L ) n (2);

[0062] In the formula: n It is an experience index (usually taken as 1~2).

[0063] Non-Darcy effect correction term c When the seepage velocity is high, the Reynolds number is high. Re Exceeding the critical value Re crit When introduced, the influence of the inertia term is corrected, and expression (3) is as follows:

[0064] c =1+ a 2· R e(3);

[0065] In the formula: a 2 is an empirical coefficient.

[0066] The revised formula for calculating the seepage velocity, expression (4), is as follows:

[0067] v z修正 =β·γ·πr / (2α 1 t)·ln(C 0 / C t ) (4);

[0068] In the formula: v z修正 For depth Z Correction value for vertical seepage velocity at the location.

[0069] (III) Modeling based on the relationship between image recognition and flow velocity

[0070] Transient electromagnetic method (TEM) can quickly obtain the resistivity distribution of a dam, but it cannot directly quantify the seepage velocity; single-hole dilution method can accurately measure the flow velocity in the pore, but only provides discrete point data. Therefore, establishing a quantitative mapping relationship between the two can realize the conversion from "resistivity image" to "seepage velocity". The quantitative mapping relationship between the two is established as follows.

[0071] 3.1 Feature Extraction from Transient Electromagnetic Transmission (TEM) Images

[0072] ① The resistivity profile generated by the transient electromagnetic method is converted into a two-dimensional grayscale image by converting the RGB image into a grayscale matrix, such as... Figure 4 As shown, expression (5) is as follows:

[0073] (5);

[0074] In the formula: I gray ( X , Z ) is a resistivity profile image in coordinates ( X , Z The grayscale value; R, G, and B are the red, green, and blue channel values, respectively; l r , l g , l b These are the coefficient values ​​corresponding to R, G, and B, respectively.X , Z For pixel coordinates, X In the horizontal direction, Z It is in the vertical direction.

[0075] ② The grayscale matrix is ​​denoised using median filtering, as shown in expression (6):

[0076] (6);

[0077] In the formula: k The radius of the filtering window; i The horizontal offset represents the step size of the filter window in the horizontal direction. j The vertical offset represents the step size of the filter window in the vertical direction.

[0078] ③ Leakage area segmentation

[0079] Otsu adaptive thresholding based on grayscale values ​​is used, and the expression (7) is as follows:

[0080] (7);

[0081] In the formula: T The threshold for segmenting the image, below T The pixels above are considered potential leakage areas. T Pixels are considered normal areas; To be the optimal threshold, , They are respectively lower than T and higher T Pixel ratio; , They are respectively , The average grayscale value of these two types of pixels.

[0082] Generate a binary mask, with the hidden danger area set to 1 and the normal area set to 0. The expression (8) is as follows:

[0083] (8);

[0084] 3.2 Drilling velocity-resistivity correlation modeling

[0085] Data pairing: Depth measured by single-well dilution method Z Vertical seepage velocity correction value at the location v z修正 With resistivity profile image in coordinates ( X , Z grayscale value I gray ( X ,Z Accurately align at the same borehole location and depth to construct a modeling dataset.

[0086] Spatial positioning: Extract the vertical distribution curve of resistivity grayscale values ​​along the borehole axis. This curve is determined by coordinates ( Xz , Z j grayscale value at ) I gray ( Xz , Z j )constitute, Xz Let be the coordinates of the borehole in the horizontal direction. Z j These are coordinates at different depths in the borehole. The single-hole dilution method measures the seepage velocity at depth intervals within the same borehole. v zj修正 This forms a discrete dataset. v zj修正 , Z j}

[0087] Depth alignment: Due to the resolution difference between the two methods, depth interpolation is required. For grayscale values... I gray ( Xz , Z j Cubic spline interpolation is used to match the sampling point depth of the dilution method. The interpolated gray values ​​and the paired datasets are given by formulas (9) and (10), respectively.

[0088] I inter ( Xz , Z j )=spline( I gray ( Xz , Z j ), Z j (9);

[0089] D={ I inter ( Xz , Z j ), v zj修正}(10)

[0090] ②Nonlinear regression modeling: Establishing seepage velocity v zj修正 With resistivity gray value I inter ( Xz , Z j A quantitative relationship model is used to reflect the low-resistance, high-velocity characteristics within the leakage channel. Weighted least squares method is employed for parameter fitting, and the objective function for fitting is:

[0091] (11);

[0092] In the formula: w i The weight value is [value], and the weight value for the high-velocity region is [value]. w i =ln( v zj修正 +1); or 1 is a proportionality coefficient, reflecting the permeability of the medium; or 2 represents the sensitivity index (typically 0.8~1.5), which reflects the intensity of the flow velocity response to changes in resistivity.

[0093] The Levenberg-Marquardt (LM) iterative method can effectively handle nonlinear least squares problems. The convergence condition of the LM algorithm is given by formula (12):

[0094] (12);

[0095] In the formula: Δ or 1 is or The change in 1; Δ or 2 is or The change in 2.

[0096] (iv) Calculation of seepage in earth-rock dams

[0097] Using formula (7), the leakage hazard zone of the entire dam profile is obtained, and then identified, segmented, and its area is extracted, such as... Figure 5 As shown. Based on the established borehole flow velocity-resistivity correlation model, the seepage rate of the entire dam profile can be calculated.

[0098] The method provided in this embodiment rapidly scans and locates potential leakage areas using transient electromagnetic methods, guiding single-hole dilution drilling in key areas and reducing ineffective drilling. Based on the traditional dilution curve model, a borehole radius correction factor and a non-Darcy effect correction term are introduced, significantly improving the accuracy of the vertical seepage profile output. A quantitative mapping model between resistivity inversion images and seepage velocity is established to achieve quantitative conversion of physical detection data into hydraulic parameters. Based on image recognition technology, the spatial distribution of seepage channels is automatically extracted, enabling rapid calculation of the total dam seepage.

Claims

1. A method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method, characterized in that, Includes the following steps: S1. Obtain resistivity profile images based on transient electromagnetic method to locate potential leakage areas; S2. Based on the leakage hazard area located by the transient electromagnetic method, determine the drilling location and depth, and calculate the seepage velocity based on the single-hole dilution method; S3. Extract features from the resistivity profile image and establish a quantitative mapping relationship between the seepage velocity and the resistivity profile image to obtain an association model; S4. Identify, segment, and extract the area of ​​the seepage hazard zone in the entire earth-rock dam profile. Based on the established seepage velocity-resistivity profile image association model, calculate the seepage volume of the entire dam profile.

2. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 1, characterized in that, In step S1, the transient electromagnetic method involves sending a pulsed magnetic field to the ground through a transmitting coil and measuring the induced secondary field during the off period. The leakage hazard area exhibits low resistance due to its high water content, forming an abnormal area in the resistivity profile.

3. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 1, characterized in that, In step S2, when calculating the seepage velocity using the single-hole dilution method, the influence of the borehole itself on the water velocity field is considered, and a borehole radius correction factor is introduced. β Non-Darcy effect correction term γ The formula for calculating flow velocity was revised.

4. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 3, characterized in that, The revised formula for calculating the flow rate in the single-hole dilution method is as follows: v z修正 = β · γ · πr / (2 α 1 t )·ln( C 0 / C t )； Among them, the borehole radius correction factor β The expression is as follows: β =(1+ r / L ) n ； Non-Darcy effect correction term γ The expression is as follows: γ =1+ a 2· Re; In the formula, v z修正 For depth Z Correction value for vertical seepage velocity at the location. C 0 For time t Conductivity at 0; C t For time t conductivity at that time; t For measuring time; r The radius of the borehole; α 1 For correction factors, L The characteristic length of the aquifer. n It is an experience index. a 2 is an empirical coefficient. Re It is the Reynolds number.

5. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 1, characterized in that, In step S3, the specific steps for extracting features from the resistivity profile image are as follows: S311. Perform two-dimensional grayscale processing on the resistivity profile generated by the transient electromagnetic method inversion, converting the RGB image into a grayscale matrix, as shown in the following expression: ； In the formula, I gray ( X , Z ) is a resistivity profile image in coordinates ( X , Z The grayscale value of ) R, G, B These are the values ​​for the red, green, and blue channels, respectively. λ r , λ g , λ b They are respectively R, G, B Corresponding coefficient value; X , Z For pixel coordinates, X In the horizontal direction, Z Vertical direction; S312. The median filtering method is used to denoise the grayscale matrix. The expression is as follows: ； In the formula: k The radius of the filtering window; i The horizontal offset represents the step size of the filter window in the horizontal direction. j The vertical offset represents the step size of the filter window in the vertical direction. S313. Leakage area segmentation: Otsu adaptive threshold segmentation based on grayscale values ​​is used to generate a binary mask, with the hidden danger area set to 1 and the normal area set to 0. The threshold segmentation expression is as follows: ； In the formula: T The threshold for segmenting the image, below T The pixels above are considered potential leakage areas. T Pixels are considered normal areas; To be the optimal threshold, , They are respectively lower than T and higher T Pixel ratio; , They are respectively , The average grayscale value of these two types of pixels.

6. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 5, characterized in that, In step S3, the method for establishing the association model is as follows: S321, Data pairing: The depth measured by the single-well dilution method... Z Vertical seepage velocity correction value at the location v z修正 With resistivity profile image in coordinates ( X , Z grayscale value I gray ( X , Z Accurately align at the same borehole location and depth to construct a modeling dataset; S322, Spatial Positioning: Extract the vertical distribution curve of resistivity grayscale values ​​along the borehole axis. This curve is derived from the coordinate system (…). Xz , Z j grayscale value at ) I gray ( Xz , Z j )constitute, Xz Let be the coordinates of the borehole in the horizontal direction. Z j To establish coordinates at different borehole depths, the single-hole dilution method measures the seepage velocity at depth intervals within the same borehole. v zj修正 This forms a discrete dataset. v zj修正 , Z j }; S323, Depth Alignment: Alignment of grayscale values I gray ( Xz , Z j Cubic spline interpolation is used to match the sampling point depth of the single-well dilution method. The expression for the interpolated grayscale value is as follows: I inter ( Xz , Z j )=spline( I gray ( Xz , Z j ), Z j ); The paired dataset expression is as follows: D={ I inter ( Xz , Z j ), v zj修正}； S324. Nonlinear Regression Modeling: Establishing Seepage Velocity v zj修正 With grayscale value I inter ( Xz , Z j A quantitative relationship model is used to reflect the low-resistance, high-velocity characteristics within the leakage channel. Weighted least squares method is employed for parameter fitting, and the objective function for fitting is: ; In the formula: w i The weight value is [value], and the weight value for the high-velocity region is [value]. w i =ln( v zj修正 +1); η 1 is a proportionality coefficient, reflecting the permeability of the medium; η 2 is the sensitivity index, which reflects the intensity of the flow velocity response to changes in resistivity.

7. The method for detecting seepage in earth-rock dams based on a combination of transient electromagnetic method and single-hole dilution method according to claim 6, characterized in that, The parameters for nonlinear regression modeling are solved using the LM iterative method. The convergence condition of the algorithm is: ； In the formula: Δ η 1 is η The change in 1; Δ η 2 is η The change in 2.

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