Methods and systems for evaluating contact area during joint shearing

Abstract

This invention discloses a method and system for evaluating the contact area during joint shearing, comprising: acquiring three-dimensional topographic point cloud data of the joint surface of a sample, and dividing the three-dimensional topographic point cloud data into multiple grid regions; determining the number of grid regions in contact during the shearing process; and using the proportion of the number of contacting grid regions to the total number of grid regions as the contact area of ​​the joint surface during the shearing process. Based on the grid division method, this invention first determines whether each small grid region is in contact, and then calculates the overall contact area of ​​the measured joint surface. This method has very high accuracy and strong application guidance significance for specific engineering examples.

Description

Technical Field

[0001] This invention relates to the field of geometric parameter measurement technology for rock mass structural surfaces, specifically to a method and system for evaluating the contact area during joint shearing. Background Technology

[0002] Most geological damage on Earth is closely related to shear failure, each instance causing loss of life and property. The evolution and mechanism of joint contact area during shearing play a crucial role in elucidating the mechanism of shear failure. Studying the evolution and mechanism of contact area during shearing is a key step in understanding the mechanism of shear failure, repairing and preventing damaged areas, and improving safety to safeguard people's lives and property. Numerous structural planes, including faults, joints, bedding, and fissures, exist in the rock masses of various engineering projects such as mines, tunnels, slopes, and water conservancy and hydropower projects. Deformation and slippage of these structural planes can lead to engineering instability, disrupting the integrity of the rock mass, significantly reducing its strength and stability, and seriously threatening people's lives and property.

[0003] When disturbed by human activities such as underground mining and construction, faults are more prone to slippage, causing serious damage to underground mining spaces and even the mine surface. Mining-induced fault slippage leading to destructive earthquakes or rockbursts is becoming a major threat to deep mining safety worldwide. Therefore, in-depth research on the failure characteristics of rock mass structural surfaces is of great significance for engineering disaster prevention and control. The contact area of ​​joint surfaces can characterize the integrity of joint surfaces. As an important fundamental parameter of rock mass joint surfaces, the contact area plays a vital role in promoting the study of joint surface failure mechanisms and providing corresponding prevention mechanisms in engineering construction.

[0004] Furthermore, extracting oil and gas from geological rock masses is a highly complex engineering project, primarily determined by the effects of seepage within the geology. Many scholars believe that joint seepage is related to both contact area and surface morphology; therefore, contact area, as a crucial parameter in joint seepage, has received considerable attention. Whether or not joints are in contact within an oilfield plays a vital role in determining whether or not extraction is feasible.

[0005] The contact area of ​​joint surfaces is an important parameter that not only affects the degree of shearing (for example, a smaller contact area of ​​joint surfaces leads to greater stress and more severe shearing), but may also affect the seepage process and even the extraction of oil and gas. Therefore, there is an urgent need for a method that can assess the true contact area of ​​joint surfaces in a geological area.

[0006] In related technologies, Chinese invention patent application CN106769791A discloses a device and method for measuring the contact area of ​​natural loess joints. This method obtains the contact area of ​​loess joints by uniformly spreading powder on the joint surface and combining it with image processing technology. Chinese invention patent application CN109948205A discloses a method for calculating joint surface roughness based on three-dimensional morphological description. This method divides the joint surface into grids, scans the elevations of the grid points to obtain elevation data of the grid points on the rock joint surface, and then analyzes and judges the three-dimensional morphological characteristics of the joint surface based on the elevation magnitude and spatial position relationship of each point with surrounding points. Different methods are then used to describe the three-dimensional morphology of the grid points on the joint surface, and their characteristic elevations are obtained. Finally, the roughness statistics of the entire joint surface are calculated using the characteristic elevations of the grid points. However, this method calculates the roughness of the joint surface, not the contact area. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to evaluate the actual contact area during the shearing process of joint surfaces.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] On the one hand, a method for evaluating the contact area during joint shearing is proposed, the method comprising:

[0010] The three-dimensional topographic point cloud data of the joint surface of the sample is obtained, and the three-dimensional topographic point cloud data is divided into multiple grid regions;

[0011] Determine the number of mesh regions that all of the stated mesh regions come into contact with during the shearing process;

[0012] The proportion of the number of contact mesh regions to the total number of mesh regions is used as the contact area of ​​the joint surface during the shearing process.

[0013] Further, determining the number of contact grid regions in all of the grid regions includes:

[0014] The formula for determining whether each grid region in all the aforementioned grid regions is in contact is expressed as: Δ Z =ΔZ2-ΔZ1+dz, where Δ Z <0 and Δ Z When the value is 0, the grid region is considered to be in contact.

[0015] In the formula: ΔZ1 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the unsheared state; ΔZ2 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the sheared state; dz is the normal deformation of the joint surface during the shearing process.

[0016] Further, the acquisition of three-dimensional topographic point cloud data of the joint surface of the sample, and the division of the three-dimensional topographic point cloud data into multiple grid regions, includes:

[0017] Before the sample is sheared, the initial three-dimensional topography point cloud data of the joint surface of the sample is obtained, and the initial three-dimensional topography point cloud data is divided into multiple grid regions.

[0018] After the sample is sheared, the three-dimensional topographic point cloud data of the joint surface of the sample after shearing is obtained, and the three-dimensional topographic point cloud data after shearing is divided into multiple grid regions.

[0019] Further, before the sample is sheared, the initial three-dimensional topographic point cloud data of the joint surface of the sample is acquired, and the initial three-dimensional topographic point cloud data is divided into multiple grid regions, including:

[0020] Before the specimen is sheared, the two joint surfaces of the specimen are scanned, and the initial three-dimensional topography point cloud data from the two scans are cropped to retain only the outermost layer, resulting in two structural surfaces U and D, where the elevation of structural surface U is greater than the elevation of structural surface D.

[0021] Using an orthogonal partitioning method, the structural plane U and structural plane D are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0022] The average elevation of all point cloud data points in each grid region is used as the coordinate elevation value of the corresponding grid region;

[0023] Subtract the coordinate elevation values ​​of each grid region corresponding to the structural surface U from those of the structural surface D to obtain the coordinate difference value of each grid region after aligning the coordinates of the upper and lower surfaces of the unsheared specimen.

[0024] Further, after the sample is sheared, the step involves acquiring post-shear three-dimensional topographic point cloud data of the joint surface of the sample, and dividing the post-shear three-dimensional topographic point cloud data into multiple grid regions, including:

[0025] After the sample is sheared, the two joint surfaces of the sample are scanned, and the initial three-dimensional topography point cloud data from the two scans are respectively cropped to retain only the outermost layer, resulting in two structural surfaces U' and D', wherein the elevation of structural surface U' is greater than the elevation of structural surface D'.

[0026] Using an orthogonal partitioning method, the structural plane U' and structural plane D' are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0027] The average elevation of all point cloud data points in each grid region is used as the coordinate elevation value of the corresponding grid region;

[0028] Subtract the coordinate elevation values ​​of each grid region corresponding to the structural surface U' and the structural surface D' to obtain the coordinate difference value of each grid region after the coordinates of the upper and lower surfaces of the sheared sample are aligned.

[0029] Furthermore, the formula for calculating the normal deformation of the joint surface during the shearing process is expressed as follows:

[0030] dz=u n -δ n

[0031] In the formula: u n δ represents the normal expansion deformation generated during the shearing process. n This represents the normal compressive deformation generated during the shearing process.

[0032] Furthermore, the formula for calculating the normal expansion deformation is expressed as follows:

[0033] u n =δ s ·tand nmob

[0034]

[0035] Where: δ s It is the shear displacement during the shearing process; d nmob The dynamic shear dilatation angle; M is the damage coefficient related to the normal stress; JRC mob JRC is the dynamic JRC parameter; JCS is the rock wall strength; σ n This represents the normal stress value applied during the shearing process.

[0036] Furthermore, the formula for calculating the normal compressive deformation is expressed as follows:

[0037]

[0038] In the formula: V m For maximum closure; K ni σ is the initial normal stiffness; n denoted as σ, representing the normal stress applied during the shearing process; and σ is the wear coefficient.

[0039] Furthermore, after using the proportion of the number of contact mesh regions to the total number of mesh regions as the contact area of ​​the joint surface during shearing, the method further includes:

[0040] Apply a layer of paint or pigment to the surface of the sample, and obtain a wear image of the contact area of ​​the sample after shearing.

[0041] The wear coefficient is corrected based on the wear image of the contact area.

[0042] Secondly, this invention proposes a contact area evaluation system during joint surface shearing, the system comprising:

[0043] The acquisition module is used to acquire three-dimensional topographic point cloud data of the joint surface of the sample and divide the three-dimensional topographic point cloud data into multiple grid regions.

[0044] A determination module is used to determine the number of mesh regions that all the mesh regions come into contact with during the shearing process;

[0045] The contact area calculation module is used to calculate the proportion of the number of contact mesh areas to the total number of mesh areas as the contact area of ​​the joint surface during shearing.

[0046] The advantages of this invention are:

[0047] (1) According to the method of mesh division, the three-dimensional topographic point cloud data of the joint surface of the sample is divided into multiple mesh regions. First, it is determined whether each mesh region is in contact, and then the proportion of the number of contacting mesh regions to the total number of mesh regions is counted as the overall contact area of ​​the joint surface. This method has very high accuracy and has strong application guidance significance in specific engineering examples.

[0048] (2) Compared with other more complex and cumbersome calculations, the present invention has a strong systematic and procedural nature, which makes it easy to use languages ​​such as Java and C++ to form a procedural calculation method. For example, the normal deformation dz during the shearing process is input, ΔZ1 is obtained from the initial scan, and ΔZ2 is obtained from the second scan after shearing. The output contact area parameter is simple and convenient for staff to obtain the contact area parameter.

[0049] (3) The normal deformation dz during the shearing process can be directly calculated using the parameters according to the algorithm in this paper. In situations where it is inconvenient to install LVDT, extensometer, etc. to measure the normal deformation during rock mass shearing, especially in the case of construction in more severe areas such as tunnels, slopes, and hydropower stations, the normal deformation during shearing can be directly calculated using some basic parameters and substituted into it. This method has strong innovation and convenience in severe engineering projects.

[0050] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating the contact area evaluation method during joint surface shearing proposed in this invention.

[0052] Figure 2 This is a schematic diagram of the overall process of the contact area evaluation method during joint surface shearing proposed in this invention;

[0053] Figure 3 These are schematic diagrams of the sample structure in this invention. (a) is a schematic diagram of a single structure, and (b) is a schematic diagram of the overall external structure.

[0054] Figure 4 This is the three-dimensional object point cloud obtained through three-dimensional scanning in this invention;

[0055] Figure 5 This is the invention of Figure 4 Joint surface point cloud after cropping the point cloud of a 3D object;

[0056] Figure 6 This is the original point cloud scanned in this invention;

[0057] Figure 7 This is the invention of Figure 6 The point cloud after meshing the original point cloud;

[0058] Figure 8 This is a schematic diagram of the elevation and difference between structural plane U and structural plane D in this invention;

[0059] Figure 9 This is a schematic diagram of the shearing process in this invention;

[0060] Figure 10 This is the image obtained by processing the surface morphology obtained from scanning in MATLAB in this invention;

[0061] Figure 11 This is a schematic diagram of the contact area evaluation system during joint surface shearing proposed in this invention. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] like Figure 1 As shown, the first embodiment of the present invention proposes a method for evaluating the contact area during joint shearing, the method comprising the following steps:

[0064] S10. Obtain the three-dimensional topographic point cloud data of the joint surface of the sample, and divide the three-dimensional topographic point cloud data into multiple grid regions.

[0065] S20. Determine the number of mesh regions that all the mesh regions contact during the shearing process;

[0066] S30. The proportion of the number of contact mesh areas to the total number of mesh areas is used as the contact area of ​​the joint surface during the shearing process.

[0067] This embodiment uses a meshing method to divide the three-dimensional topographic point cloud data of the joint surface of the sample into multiple mesh regions. First, it determines whether each mesh region is in contact, and then it counts the proportion of the number of contacting mesh regions to the total number of mesh regions, which is taken as the overall contact area of ​​the joint surface. This method has very high accuracy. The contact area calculated above can be used to calculate the contact area and even permeability parameters of the rock and soil joint surface during shearing as needed, which provides assistance for mining and tunneling and has strong application guidance significance for specific engineering examples.

[0068] Compared with traditional methods of manually estimating contact area, the subjective error caused by human factors is greatly reduced. The results obtained in this embodiment can be stored more conveniently on a computer or USB flash drive, making the data easy to carry and transmit. Errors and discrepancies caused during the calculation process can also be corrected in a timely manner, facilitating the transmission of accurate information. This provides a guarantee for obtaining the true contact area during joint shearing and contributes to engineering applications such as slope protection, mining construction, and oil and gas energy extraction.

[0069] In one embodiment, step S20: determining the number of contact grid regions in all the grid regions includes:

[0070] The formula for determining whether each grid region in all the aforementioned grid regions is in contact is expressed as: Δ Z =ΔZ2-ΔZ1+dz, where Δ Z <0 and Δ Z When the value is 0, the grid region is considered to be in contact.

[0071] In the formula: ΔZ1 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the unsheared state; ΔZ2 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the sheared state; dz is the normal deformation of the joint surface during the shearing process.

[0072] It should be noted that if Δ Z If the value is greater than 0, then the grid area is determined to be untouched.

[0073] It should be noted that in the matrix, for the calculation of each grid, after substituting the corresponding parameters into this formula, it is first determined whether each small grid is in contact. Then, the total contact area is obtained based on the number of small grids in contact. Based on this principle, in actual calculation, the elevation of each small grid is treated as a parameter in the matrix, and the matrix is ​​subtracted to facilitate the calculation.

[0074] It should be noted that this method is a procedural calculation process. Compared with other more complex and cumbersome calculations, this method has strong systematicity and procedurality, which makes it easy to form a procedural calculation method by programming languages ​​such as Java and C++. For example, the normal deformation dz during the shearing process is input, ΔZ1 is obtained from the initial scan, and ΔZ2 is obtained from the second scan after shearing. The output is the contact area parameter, which is simple and convenient for staff to obtain the contact area parameter.

[0075] In one embodiment, such as Figure 2 As shown, step S10 involves acquiring three-dimensional topographic point cloud data of the joint surface of the sample and dividing the three-dimensional topographic point cloud data into multiple grid regions. This specifically includes the following steps:

[0076] S11. Before the sample is sheared, the initial three-dimensional topography point cloud data of the joint surface of the sample is obtained, and the initial three-dimensional topography point cloud data is divided into multiple grid regions.

[0077] S12. After the sample is sheared, the three-dimensional topography point cloud data of the joint surface of the sample after shearing is obtained, and the three-dimensional topography point cloud data after shearing is divided into multiple grid regions.

[0078] It should be noted that, as Figures 3 to 7 As shown, this embodiment can scan the joint surface of a soil and rock sample using a 3D laser scanner to obtain the 3D topographic point cloud data and 3D coordinate values ​​of the joint surface. Mesh division refers to dividing the 3D coordinate values ​​of the joint surface of the sample into blocks according to the region after scanning the sample. The division method adopts orthogonal division, dividing the point cloud data of the entire 100×100mm region into small grids of size 1×1mm.

[0079] It should be noted that this orthogonal partitioning method was implemented using code in MATLAB. The partitioning principle is determined by the size of the point cloud and the accuracy of the scanning instrument; however, each grid must contain at least one point cloud data point, making each grid a sub-region of the point cloud. The elevation of this sub-region is recorded as the average elevation of the points contained within it. Thus, each grid will have an elevation value, resulting in an m x n grid matrix, where m is the number of rows and n is the number of columns.

[0080] It should be noted that the surface morphology of the structure obtained from 3D laser scanning is a very advanced technology. The feasibility and realism of the obtained surface morphology point cloud coordinate parameters are very high, showing significant advancement and accuracy compared to previous methods. Using the accompanying MATLAB algorithm, the corresponding joint surface contact area value can be obtained simply by inputting the relevant parameters, demonstrating high reliability. The operation can be performed using a testing machine, 3D laser scanner, MATLAB, point cloud software, etc. Compared to traditional manual estimation methods of contact area, the subjective error caused by human factors is greatly reduced. The results can be more conveniently stored on a computer or USB flash drive, facilitating data portability and transmission. Errors and discrepancies during the calculation process can be promptly corrected, ensuring accurate information transmission. This provides assurance for determining the true contact area during joint shearing, contributing to engineering applications such as slope protection, mining construction, and oil and gas energy extraction.

[0081] In one embodiment, step S11: before the sample is sheared, acquiring initial three-dimensional topographic point cloud data of the joint surface of the sample, and dividing the initial three-dimensional topographic point cloud data into multiple grid regions, specifically includes the following steps:

[0082] S111. Before the sample is sheared, scan the two joint surfaces of the sample, and cut the initial three-dimensional topography point cloud data of the two scans to retain only the outermost layer, to obtain two structural surfaces U and D, wherein the elevation of structural surface U is greater than the elevation of structural surface D.

[0083] It should be noted that for a smooth and flat cubic rock sample with dimensions of 100×100×100mm, after splitting along the center line to form two rock samples, each small rock sample will have an uneven random joint surface due to the splitting. The two joint surfaces scanned are these uneven joint surfaces in each rock sample. These two joint surfaces are also the corresponding joint surfaces in the two rock blocks, one above the other, during the shearing process. The initial scan is based on these two joint surfaces.

[0084] It should be noted that, in the initial uncut state, the sample is placed in a fixed position on the table and scanned by a 3D laser scanner. The result is a 3D point cloud of the object. Point cloud software such as Cloudcompare is needed to perform a cropping process to crop the 3D point cloud object to retain only the outermost layer. This retained surface is the joint surface that is required.

[0085] The elevation of surface U is the distance from the point cloud on surface U to the bottom along the vertical direction. This elevation is marked with a marker near the side of the surface. The other surface is named surface D. The elevation of surface D is the distance from the bottom along the vertical direction of the point cloud coordinates on surface D. This elevation is also marked with a marker on the side.

[0086] S112. Using an orthogonal partitioning method, the structural surface U and structural surface D are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0087] It should be noted that in this embodiment, the point cloud data corresponding to structural surfaces U and D are imported into MATLAB for subsequent operations. In MATLAB, the meshing is performed in an orthogonal manner, that is, the 100×100mm joint surface is divided into 1×1mm small grids. The elevation on surface U is the average distance of each small grid on surface U from the bottom surface along the vertical direction. The elevation on surface D is the average distance of the point cloud coordinates in each small grid on surface D from the bottom surface along the vertical direction.

[0088] Furthermore, the joint surfaces U and D are defined as follows:

[0089]

[0090] In the formula: U 11 This represents the elevation values ​​of the U-joint surfaces scanned in the rock sample, in the first row and first column of the matrix. mn Represents the elevation value of the small grid in the m-th row and n-th column of the matrix for the U-joint surface scanned in the rock sample; D 11 This represents the D-joint surface scanned in the rock sample, with the elevation values ​​of the first grid in the first row and first column of the matrix. mn This represents the elevation value of the small grid in the m-th row and n-th column of the matrix, representing the D-joint surface scanned in the rock sample.

[0091] S113. Take the average elevation of all point cloud data points in each grid region as the coordinate elevation value of the corresponding grid region;

[0092] S114. Subtract the coordinate elevation values ​​of each grid region corresponding to the structural surface U and the structural surface D to obtain the coordinate difference value of each grid region after the coordinates of the upper and lower surfaces of the unsheared specimen are aligned.

[0093] Specifically, such as Figure 8 , Figure 10 As shown, the x and y coordinates of the grid regions of structural plane U and structural plane D are mapped one-to-one, and the elevation values ​​of each grid are subtracted accordingly. The resulting coordinate difference matrix is ​​ΔZ1. Specifically, the formula for calculating ΔZ1 is: ΔZ1 = Z U1-Z D1 Among them, Z U1 Z represents the elevation value of the U-shaped surface of the specimen in the unsheared state. D1 This represents the elevation value of the D structural surface of the sample in the unsheared state.

[0094] In one embodiment, step S12: after shearing the sample, acquiring the post-shear three-dimensional topography point cloud data of the joint surface of the sample, and dividing the post-shear three-dimensional topography point cloud data into multiple grid regions, specifically includes the following steps:

[0095] S121. After the sample is sheared, the two joint surfaces of the sample are scanned, and the initial three-dimensional topography point cloud data of the two scans are respectively cropped to retain only the outermost layer, resulting in two structural surfaces U' and D', wherein the elevation of structural surface U' is greater than the elevation of structural surface D'.

[0096] It should be noted that the two joint surfaces scanned before and after shearing are different. Due to the shearing process, the U-surface and D-surface of the rock sample have undergone wear and shear dilation, so the joint surfaces will also be different. The sample is scanned once before shearing and once again after shearing.

[0097] S122. Using an orthogonal partitioning method, the structural surface U' and structural surface D' are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0098] S123. Take the average elevation of all point cloud data points in each grid region as the coordinate elevation value of the corresponding grid region;

[0099] S124. Subtract the coordinate elevation values ​​of each grid region corresponding to the structural surface U' and the structural surface D' to obtain the coordinate difference value of each grid region after the coordinates of the upper and lower surfaces of the sheared sample are aligned.

[0100] It should be noted that after the sample is sheared, it is placed on the same table as before the shearing scan, and the surface morphology of the joint surface after shearing is scanned again using a 3D laser scanner. The sheared sample obtained by the 3D laser scanner is also a 3D point cloud. It needs to be trimmed using point cloud software such as Cloudcompare to retain only the outermost layer. This retained surface is the required joint surface. Then, this joint surface is imported into MATLAB for mesh generation. The point cloud data of the scanned structural surface U' is then processed in MATLAB. In MATLAB, the joint surface is divided into 1×1mm grids using an orthogonal method. The elevation of the U' surface is the distance from the bottom surface along the vertical direction of each small grid on the U' surface. The scanned point cloud data is also divided into grids using an orthogonal method in MATLAB, that is, the 100×100mm joint surface is divided into 1×1mm grids. The elevation of the D' surface is the distance from the bottom surface along the vertical direction of the point cloud coordinates in each small grid on the D' surface. The elevation of the structural surface U' is greater than the elevation of the structural surface D'.

[0101] The elevation values ​​of each small grid in the U' and D' surfaces are calculated. Then, using the programmed algorithm, considering shear displacement, the upper and lower surfaces are aligned. The coordinate elevation values ​​of each small grid corresponding to the U' and D' surfaces are subtracted. This yields the coordinate difference matrix ΔZ2 of the grid after the sheared specimen's U' and D' surfaces are aligned. The calculation formula is: ΔZ2 = Z U2 -Z D2 Among them, Z U2 Z represents the elevation value of the U' structural surface of the specimen after shearing. D2 This represents the elevation value of the structural surface D' of the sample after shearing.

[0102] In one embodiment, such as Figure 10 As shown, the formula for calculating the normal deformation of the joint surface during the shearing process is expressed as follows:

[0103] dz=u n -δ n

[0104] In the formula: u n δ represents the normal expansion deformation generated during the shearing process. n This represents the normal compressive deformation generated during the shearing process.

[0105] In one embodiment, the normal expansion deformation amount u n The calculation formula is expressed as:

[0106] u n =δ s ·tand nmob

[0107]

[0108] Where: δ s It refers to the shear displacement during the shearing process, in mm; d nmob The dynamic shear dilatation angle; M is the damage coefficient related to the normal stress; JRC mob σ is the dynamic JRC parameter; JCS is the rock wall strength, which can be approximated by the uniaxial compressive strength of the rock sample, and the uniaxial compressive strength of the rock sample is obtained from a uniaxial compression test; n The applied normal stress value is used in the calculation, which is the value of the applied normal stress during the shearing process.

[0109] Specifically, M is the damage coefficient related to the normal stress. When the stress state is set to 1, 2, and 3 MPa, M is 2.0. When the stress state is set to 1, 5, and 10 MPa, M is 1.0, 2.0, and 2.0, respectively.

[0110] JRC mob These are dynamic JRC parameters, specifically the JRC parameters corresponding to different shear displacements. In other words, they are the JRC parameters obtained after scanning the specimen following shearing and processing. mob The specific calculation is as follows: after cutting, first take the coordinate values ​​of the U' surface point cloud obtained by scanning, then divide the U' surface into small grids of size 1×1mm, and calculate in each small grid using the following JRC formula:

[0111] JRC = 32.2 + 32.47logz2

[0112]

[0113] Furthermore, this formula can be used in MATLAB to first calculate the z2 value from the scanned joint surface point cloud data, then calculate the JRC of the U' and D' surfaces based on the obtained z2 value, and finally take the average of the JRC calculated for the U' and D' surfaces to obtain the JRC. mob L represents the length of the section line along the calculation direction in the joint surface; for a 100×100mm joint surface, the length is 100mm; x i Let x be the x-coordinate of the i-th point in the profile along the calculation direction; y be the x-coordinate of the i-th point. i Let x be the y-coordinate of the i-th point in the profile along the calculation direction; i+1 Here are the x-coordinates of the (i+1)th point in the profile along this calculation direction; y-coordinates are... i+1 y is the y-coordinate of the (i+1)th point in the profile along the calculation direction; N is the number of sampling points in the profile along the calculation direction.

[0114] In one embodiment, the formula for calculating the normal compressive deformation is expressed as:

[0115]

[0116] In the formula: V m For maximum closure; K ni σ is the initial normal stiffness; n denoted as σ, representing the normal stress applied during the shearing process; and σ is the wear coefficient.

[0117] Furthermore, the maximum closure V m and initial normal stiffness K ni The calculation formula is:

[0118]

[0119] In the formula: A, B, C, D are the values ​​used to calculate V. m The constant values ​​in the empirical formula are: A = -0.296 ± 0.1258, B = -0.0056 ± 0.0022, C = -2.241 ± 0.3504, D = -0.245 ± 0.1086; JRC is the surface roughness of the specimen during the initial scan. The point cloud coordinates of the scan are calculated in MATLAB according to the formula and algorithm to obtain JRC; that is, the JRC of surfaces U and D are calculated and the average value is taken; a j The initial opening value is calculated using the corresponding theoretical formula, which includes parameters such as JRC, JCS, and uniaxial compressive strength σ. c These three parameters are related to u n The methods for calculating or obtaining intermediate parameters are the same.

[0120] It should be noted that the normal deformation dz during the shearing process can be directly calculated using the parameters according to the algorithm in this paper. In situations where it is inconvenient to install LVDT, extensometers, etc. to measure the normal deformation of rock mass during shearing, especially in construction in more challenging areas such as tunnels, slopes, and hydropower stations, the normal deformation during shearing can be directly calculated using some basic parameters and then substituted into the algorithm. This method has strong innovation and convenience in challenging engineering projects.

[0121] In one embodiment, after step S30: using the proportion of the number of contact mesh regions to the total number of mesh regions as the contact area of ​​the joint surface during shearing, the method further includes:

[0122] Apply a layer of paint or pigment to the surface of the sample, and obtain a wear image of the contact area of ​​the sample after shearing.

[0123] The wear coefficient is corrected based on the wear image of the contact area.

[0124] It should be noted that n is related to the material type, degree of weathering, roughness, and loading history. For gypsum of the same type and under the same normal loading conditions, the material is gypsum, and the degree of weathering and roughness are the same. Therefore, one sample is selected for testing, and the value of n is measured and represented by 0.7. The value is then continuously corrected based on the contact area wear diagram. The specific correction steps are as follows: During the shearing process, the contact area diagram of the specimen surface can be obtained according to the theoretical formula. Alternatively, applying a thin layer of paint or pigment to the specimen surface can be used to verify the wear of the specimen surface after shearing.

[0125] It should be noted that the method in this embodiment is based on modern science and technology, and compared with traditional methods, it is forward-looking; and with the development of science and technology, it also has greater possibilities, development and progress; compared with the unchanging calculation of traditional methods, this technology has the characteristic of continuous updating, and the accuracy of calculation will be further improved; with the development of science and technology, and with the exploration and progress of software, it can be improved to be more convenient and efficient in each step and process.

[0126] like Figure 11 As shown, the second embodiment of the present invention also proposes a contact area evaluation system during joint surface shearing, the system comprising:

[0127] The acquisition module 10 is used to acquire three-dimensional topographic point cloud data of the joint surface of the sample and divide the three-dimensional topographic point cloud data into multiple grid regions.

[0128] Module 20 is used to determine the number of mesh regions that all the mesh regions come into contact with during the shearing process;

[0129] The contact area calculation module 30 is used to calculate the proportion of the number of contact mesh areas to the total number of mesh areas as the contact area of ​​the joint surface during the shearing process.

[0130] This embodiment uses a meshing method to divide the three-dimensional topographic point cloud data of the joint surface of the sample into multiple mesh regions. First, it determines whether each mesh region is in contact, and then it counts the proportion of the number of contacting mesh regions to the total number of mesh regions, which is taken as the overall contact area of ​​the joint surface. This method has very high accuracy. The contact area calculated above can be used to calculate the contact area and even permeability parameters of the rock and soil joint surface during shearing as needed, which provides assistance for mining and tunneling and has strong application guidance significance for specific engineering examples.

[0131] In one embodiment, the determining module 20 is specifically used for:

[0132] The formula for determining whether each grid region in all the aforementioned grid regions is in contact is expressed as: Δ Z=ΔZ2-ΔZ1+dz, where Δ Z <0 and Δ Z When the value is 0, the grid region is considered to be in contact.

[0133] In the formula: ΔZ1 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the unsheared state; ΔZ2 is the coordinate difference matrix of the grid region after the coordinates of the upper and lower surfaces of the specimen are aligned in the sheared state; dz is the normal deformation of the joint surface during the shearing process.

[0134] In one embodiment, the acquisition module 10 includes:

[0135] The first acquisition unit is used to acquire the initial three-dimensional topography point cloud data of the joint surface of the sample before the sample is sheared, and to divide the initial three-dimensional topography point cloud data into multiple grid regions.

[0136] The second acquisition unit is used to acquire the three-dimensional topographic point cloud data of the joint surface of the sample after shearing, and to divide the three-dimensional topographic point cloud data after shearing into multiple grid regions.

[0137] In one embodiment, the first acquisition unit is specifically used to perform the following steps:

[0138] Before the specimen is sheared, the two joint surfaces of the specimen are scanned, and the initial three-dimensional topography point cloud data from the two scans are cropped to retain only the outermost layer, resulting in two structural surfaces U and D, where the elevation of structural surface U is greater than the elevation of structural surface D.

[0139] Using an orthogonal partitioning method, the structural plane U and structural plane D are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0140] The average elevation of all point cloud data points in each grid region is used as the coordinate elevation value of the corresponding grid region;

[0141] Subtracting the coordinate elevation values ​​of each grid region corresponding to structural surface U and structural surface D yields the coordinate difference value of each grid region after aligning the coordinates of the upper and lower surfaces of the unsheared specimen.

[0142] In one embodiment, the second acquisition unit is specifically used to perform the following steps:

[0143] After the sample is sheared, the two joint surfaces of the sample are scanned, and the initial three-dimensional topography point cloud data from the two scans are respectively cropped to retain only the outermost layer, resulting in two structural surfaces U' and D', wherein the elevation of structural surface U' is greater than the elevation of structural surface D'.

[0144] Using an orthogonal partitioning method, the structural plane U' and structural plane D' are divided into multiple grid regions, wherein each grid region falls into at least one point cloud data point;

[0145] The average elevation of all point cloud data points in each grid region is used as the coordinate elevation value of the corresponding grid region;

[0146] Subtract the coordinate elevation values ​​of each grid region corresponding to the structural surface U' and the structural surface D' to obtain the coordinate difference value of each grid region after the coordinates of the upper and lower surfaces of the sheared sample are aligned.

[0147] In one embodiment, the formula for calculating the normal deformation of the joint surface during the shearing process is expressed as follows:

[0148] dz=u n -δ n

[0149] In the formula: u n δ represents the normal expansion deformation generated during the shearing process. n This represents the normal compressive deformation generated during the shearing process.

[0150] In one embodiment, the formula for calculating the normal expansion deformation is expressed as:

[0151] u n =δ s ·tand nmob

[0152]

[0153] Where: δ s It is the shear displacement during the shearing process; d nmob The dynamic shear dilatation angle; M is the damage coefficient related to the normal stress; JRC mob JRC is the dynamic JRC parameter; JCS is the rock wall strength; σ n This represents the normal stress value applied during the shearing process.

[0154] In one embodiment, the formula for calculating the normal compressive deformation is expressed as:

[0155]

[0156] In the formula: V m For maximum closure; K ni σ is the initial normal stiffness; n denoted as σ, representing the normal stress applied during the shearing process; and σ is the wear coefficient.

[0157] In one embodiment, the system further includes a correction module, specifically used for:

[0158] Apply a layer of paint or pigment to the surface of the sample, and obtain a wear image of the contact area of ​​the sample after shearing.

[0159] The wear coefficient is corrected based on the wear image of the contact area.

[0160] It should be noted that other embodiments or implementation methods of the contact area evaluation system during joint surface shearing described in this invention can refer to the above-described method embodiments, and will not be repeated here.

[0161] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0162] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0163] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for evaluating contact area in a joint plane shear process, characterized by, The method comprises: acquiring three-dimensional topography point cloud data of a sample joint surface, and dividing the three-dimensional topography point cloud data into a plurality of grid regions; determining the number of grid regions that contact during the shearing process, including determining whether each of the grid regions is in contact, expressed in formula as: Δ Z = ΔZ2- ΔZ1+ dz, where Δ Z <0 and Δ Z = 0, the grid region is determined to be in contact; in the formula: ΔZ1 is the coordinate difference matrix of the grid region after the upper and lower surface coordinates of the un-sheared sample are aligned; ΔZ2 is the coordinate difference matrix of the grid region after the upper and lower surface coordinates of the sample after shearing are aligned; and dz is the normal deformation amount of the joint surface during the shearing process. the proportion of the number of contact grid regions to the total number of grid regions is taken as the contact area of the joint surface in the shearing process.

2. The method of claim 1, wherein, The acquisition of the three-dimensional topography point cloud data of the sample joint surface and the division of the three-dimensional topography point cloud data into a plurality of grid regions comprise: Before the sample is not sheared, the initial three-dimensional topography point cloud data of the sample joint surface is acquired, and the initial three-dimensional topography point cloud data is divided into a plurality of grid regions; After the sample is sheared, the three-dimensional topography point cloud data of the sample joint surface after shearing is acquired, and the three-dimensional topography point cloud data after shearing is divided into a plurality of grid regions.

3. The method of claim 2, wherein, The acquisition of the initial three-dimensional topography point cloud data of the sample joint surface before the sample is not sheared and the division of the initial three-dimensional topography point cloud data into a plurality of grid regions comprise: Before the sample is not sheared, two joint surfaces of the sample are scanned, and the initial three-dimensional topography point cloud data scanned twice is respectively cut to retain only the topmost layer to obtain two structure surfaces U and D, wherein the elevation of the structure surface U is greater than the elevation of the structure surface D; The structure surface U and the structure surface D are respectively divided into a plurality of grid regions by using an orthogonal division method, wherein each grid region falls into at least one point cloud data point; The average value of the elevations of all point cloud data points in each grid region is taken as the coordinate elevation value of the corresponding grid region; The coordinate elevation values of each grid region corresponding to the structure surface U and the structure surface D are subtracted to obtain the coordinate difference value of each grid region after the upper and lower surface coordinates of the sample in the un-sheared state are aligned.

4. The method of claim 2, wherein, The acquisition of the three-dimensional topography point cloud data of the sample joint surface after shearing and the division of the three-dimensional topography point cloud data after shearing into a plurality of grid regions comprise: After the sample is sheared, two joint surfaces of the sample are scanned, and the initial three-dimensional topography point cloud data scanned twice is respectively cut to retain only the topmost layer to obtain two structure surfaces U' and D', wherein the elevation of the structure surface U' is greater than the elevation of the structure surface D'; The structure surface U' and the structure surface D' are respectively divided into a plurality of grid regions by using an orthogonal division method, wherein each grid region falls into at least one point cloud data point; The average value of the elevations of all point cloud data points in each grid region is taken as the coordinate elevation value of the corresponding grid region; The coordinate elevation values of each grid region corresponding to the structure surface U' and the structure surface D' are subtracted to obtain the coordinate difference value of each grid region after the upper and lower surface coordinates of the sample after shearing are aligned.

5. The method of claim 1, wherein, The calculation formula of the normal deformation amount of the joint surface in the shearing process is represented as: dz = u n -δ n where: u n is the normal dilatational deformation generated during shearing; δ n is the normal compressive deformation generated during shearing.

6. The method of claim 5, wherein, The calculation formula of the normal expansion deformation amount is represented as: u n = δ s · tan d nmob where δ s is the shear displacement during shearing; d nmob is the dynamic dilatancy angle; M is the damage coefficient related to the normal stress; JRC mob is the dynamic JRC parameter; JCS is the rock wall rock strength; σ n is the normal stress value applied during shearing.

7. The method of claim 5, wherein, The calculation formula of the normal compression deformation amount is represented as: where: V m K is the maximum closure; K ni K is the initial normal stiffness; σ n K is the normal stress value applied during shearing; n is the wear coefficient.

8. The method of claim 7, wherein, After the proportion of the number of contact grid regions to the total number of grid regions is taken as the contact area of the joint surface in the shearing process, the method further comprises: A layer of paint or pigment is applied to the surface of the sample, and a contact area wear image of the sample after shearing is acquired; The wear coefficient is corrected based on the contact area wear image.

9. A system for evaluating contact area during joint plane shear, comprising: The system comprises: An acquisition module is configured to acquire three-dimensional topography point cloud data of a test sample joint surface, and divide the three-dimensional topography point cloud data into a plurality of grid regions; determining module for determining the number of grid regions contacting in the shearing process of all the grid regions, including judging whether each grid region in all the grid regions is contacting, expressed as: Δ z = ΔZ2- ΔZ1+ dz, wherein Δ z <0 and Δ z = 0, the grid region is determined as contacting; in the formula: ΔZ1 is the coordinate difference matrix of the grid region after the upper and lower surface coordinates of the un-sheared sample are aligned; ΔZ2 is the coordinate difference matrix of the grid region after the upper and lower surface coordinates of the sample are aligned after shearing; and dz is the normal deformation amount of the joint surface in the shearing process. A contact area calculation module is configured to take the proportion of the number of contact grid regions to the total number of grid regions as the contact area of the joint surface in the shearing process.

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