Top plate characteristic curve accurate determination method based on similar material test

Abstract

The invention provides a method for accurately measuring a roof characteristic curve based on a similar material test, and relates to the field of underground mineral resource exploiting.According to the method, the test is conducted through similar material simulation, a sample similar to an ore body can be determined through different material matching schemes and preset similarity coefficients, and the sample can be accurately measured. And pouring an ore body three-dimensional model, thereby being capable of adapting to complex and changeable surrounding rock conditions, providing theoretical guidance for obtaining a support scheme, simulating the support force of an expansion strut by arranging a jack structure, and drawing a roof characteristic curve of the support force and roof displacement by adjusting the support force of the jack and the vertical load of a loading system. In the experiment process, the experiment can be controlled to be carried out in the same stope, the material loss is reduced, and meanwhile, the influence of other factors on the result is also reduced. Meanwhile, the technical scheme is high in construction efficiency, and compared with a field test mode, the test period is short, and the result is more visual.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underground mineral resources exploitation, in particular to a method for accurately determining roof property curve based on similar material test. BACKGROUND

[0002] The existing mineral resources are not only extremely rich in reserves, but also widely distributed. These valuable mineral resources are an important foundation support for the vigorous development of modern industry and the continuous progress of society. Among the numerous metal veins, gently inclined veins account for a high proportion. In the process of mining gently inclined veins at depth, the stability control of the roof of the stope is a key and challenging problem. To effectively solve this problem, previous researchers have proposed an innovative pre-stressed expansion prop support scheme. The prop mainly realizes the pressure relief support function of the roof by the specific chemical reaction of the bottom expansion agent, to relieve the pressure borne by the roof of the stope and ensure the safe progress of the mining operation.

[0003] However, in actual field application, different expansion agent ratios will result in different pre-stresses output by the pre-stressed expansion prop. This difference in pre-stress will have a significant impact on the control effect of the roof. If the pre-stress is too small, it cannot effectively support the roof, resulting in deformation or even collapse of the roof and other safety hazards; while if the pre-stress is too large, it may cause excessive extrusion of the roof, even penetrate the roof rock layer and cause damage, and then trigger other potential geological disasters. Therefore, in order to determine the optimal pre-stress support scheme, it is particularly important to accurately obtain the property curve of the roof. The roof property curve can intuitively reflect the mechanical response characteristics of the roof under different support conditions, and has important guiding significance for optimizing support parameters, improving support effect, and improving the economic benefits of mining.

[0004] At present, the existing roof property test methods mainly adopt two ways of static loading or numerical simulation, but both methods have obvious limitations. The static loading method is to load test the roof model in the laboratory environment, but this method cannot simulate the dynamic changes of the support force of the prop in the actual mining process. In the actual underground mining process, as the mining operation advances, the pressure borne by the roof of the stope is constantly changing, and the support force of the prop will also be dynamically adjusted. Due to the limitations of the test conditions, the static loading method cannot accurately reflect this dynamic change process, so there is a large deviation between the test results and the actual situation.

[0005] The numerical simulation method is based on certain theoretical assumptions and simulates the mechanical behavior of the roof through computer software. Although the numerical simulation can predict the mechanical response of the roof to a certain extent, it is difficult to accurately reflect the development of rock mass fractures and nonlinear failure characteristics. In the underground rock mass, due to the influence of various factors such as geological structure and mining disturbance, there are a large number of fractures and joints in the rock mass. The development and expansion process of these fractures has a high degree of nonlinearity. The numerical simulation method often simplifies these complex geological conditions, resulting in a large error between the simulation results and the actual situation.

[0006] In addition, the traditional test equipment also has limitations in obtaining roof characteristic data in industrial sites. In actual mining in the field, it is difficult to find a stope with completely identical geological and mining conditions, which makes the test results susceptible to interference from other factors such as differences in geological structure and different mining processes, thereby reducing the reliability and accuracy of the test results.

[0007] In order to overcome the shortcomings of the above methods, some people have proposed a method of combining similar material tests with stress and displacement monitoring of the roof to obtain the roof characteristic curve. Similar material tests are a method of simulating the underground mining process in a laboratory environment by creating a model similar in mechanical properties to the actual rock mass, thereby obtaining the mechanical response data of the roof. However, this method also faces many difficulties in practical application. However, even in similar material tests, it is difficult to ensure that each test model is identical to the actual excavation conditions due to slight differences in various factors such as manufacturing process and loading conditions during the test, resulting in poor repeatability of the test results. It is impossible to simultaneously obtain the multi-parameter coupling response of support force-roof displacement-fracture expansion. In the actual mechanical behavior of the stope roof, the three parameters of support force, roof displacement, and fracture expansion are interrelated and influence each other. For example, changes in support force will cause changes in roof displacement, and changes in roof displacement will further affect the expansion of fractures. Therefore, only by simultaneously obtaining the coupling response data of these three parameters can the mechanical properties of the roof be fully and accurately understood. However, due to technical limitations, the current similar experimental method cannot achieve this function, affecting the integrity and accuracy of the test data. SUMMARY

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for accurately determining the roof characteristic curve based on similar material tests, comprising:

[0009] Step 1: Determine the similarity coefficient between the ore body and the three-dimensional model of the ore body, which includes the geometric similarity coefficient and the bulk density similarity coefficient;

[0010] Step 2: according to a plurality of material proportioning schemes, a plurality of samples of the ore body three-dimensional model are prepared, and according to a similarity coefficient, a target sample is determined and the ore body three-dimensional model is poured, the ore body three-dimensional model being a cuboid model;

[0011] Step 3: curing and surface treatment are performed on the ore body three-dimensional model to obtain a treated ore body three-dimensional model;

[0012] Step 4: according to the size and position of a stope region designed in advance, the treated ore body three-dimensional model is excavated to obtain an ore body three-dimensional model after stope excavation;

[0013] The stope region penetrates two parallel planes of the treated ore body three-dimensional model, and the ore body three-dimensional model after stope excavation generates four planes in the stope region.

[0014] Step 5: a jack is placed in the stope region, a high-precision force sensor is placed below the jack, and an existing loading system is placed above the stope region and on the outer surface of the ore body three-dimensional model after stope excavation;

[0015] The jack is used to apply a support force above the stope region, and the loading system is used to apply a vertical load above the stope region, wherein the plane directly contacted by the jack to apply the support force is the roof.

[0016] Step 6: according to a preset gradient, the vertical load is increased by the loading system, the support force is increased by the jack, and the support force is collected and monitored in real time by the high-precision force sensor, so that the support force and the vertical load are equal in size until the support force and the vertical load reach the original rock stress.

[0017] Step 7: the support force of the jack is gradually reduced according to a preset gradient, the maximum displacement of the roof is calculated, and a curve of the support force and the maximum displacement, i.e., a roof characteristic curve, is generated.

[0018] Optionally, the geometric similarity coefficient is expressed as:

[0019] ;

[0020] wherein, represents the length of the ore body, represents the length of the ore body three-dimensional model;

[0021] Optionally, the bulk density similarity coefficient is expressed as:

[0022] ;

[0023] wherein, represents the bulk density of the ore body, Bulk density of the ore body three-dimensional model.

[0024] Optionally, the target sample is determined according to the similarity coefficient in step 2, and the ore body three-dimensional model is cast, comprising:

[0025] The bulk density similarity coefficient of each sample is calculated, the sample within the preset numerical range of the bulk density similarity coefficient is obtained as the target sample, and the ore body three-dimensional model is cast according to the geometric similarity coefficient and the material proportioning scheme of the target sample.

[0026] Specifically, the bulk density of the ore body and the preset numerical range of the bulk density similarity coefficient are obtained, the bulk density of the sample is measured, the ratio between the bulk density of the ore body and the bulk density of the sample is calculated, the bulk density similarity coefficient of the sample is obtained, and the bulk density similarity coefficient of each sample is obtained. The sample within the preset numerical range of the bulk density similarity coefficient is obtained as the target sample, the length of the ore body and the preset geometric similarity coefficient are obtained, the length of the ore body three-dimensional model is calculated, and the ore body three-dimensional model is cast based on the length of the ore body three-dimensional model and the material proportioning scheme of the target sample.

[0027] Optionally, step 3 specifically comprises:

[0028] The ore body three-dimensional model is covered with a plastic film, and water is sprinkled to keep the ore body three-dimensional model moist. After the cured ore body three-dimensional model is dried, a layer of white paint is uniformly sprayed on the surface of the ore body three-dimensional model, and after the white paint is dried, black speckles are sprayed again to obtain a treated ore body three-dimensional model.

[0029] Optionally, step 5 specifically comprises:

[0030] After the stope is excavated, a jack is placed on a first plane in the ore body three-dimensional model, the first plane is any one of the four planes generated in the stope area, and a steel plate and a high-precision force sensor are sequentially arranged between the first plane and the jack. The other end of the jack is in contact with a second plane, the second plane is a plane parallel to the first plane among the four planes generated in the stope area, the second plane is the roof, and a steel plate is arranged between the other end of the jack and the second plane. An existing loading system is arranged on a target plane of the ore body three-dimensional model after the stope is excavated, the target plane is a plane parallel to the second plane and closest to the second plane among the external planes of the ore body three-dimensional model after the stope is excavated.

[0031] Optionally, step 7 specifically comprises:

[0032] Gradually reduce the supporting force of the jack according to the preset gradient until the roof is damaged or the supporting force is reduced to 0, the supporting force is collected and monitored in real time through the high-precision force sensor, the roof image is collected in real time through the high-speed camera instrument in the VIC-3D speckle displacement monitoring system, the VIC-3D software in the VIC-3D speckle displacement monitoring system is used for image processing of the roof, the maximum displacement of the roof corresponding to each supporting force is obtained, and a curve of the supporting force and the maximum displacement, i.e. the roof characteristic curve, is generated.

[0033] Optionally, the in-situ rock stress is calculated by the following method:

[0034] The self-weight stress q of the ore body is calculated p , and is realized by the following formula:

[0035] q p = γ p H ;

[0036] Wherein, The bulk density of the ore body is represented by H, and the actual stope depth of the ore body is represented by H.

[0037] The geometric similarity coefficient and the bulk density similarity coefficient are multiplied to obtain the stress similarity coefficient, and the self-weight stress of the ore body is multiplied by the stress similarity coefficient to obtain the in-situ rock stress.

[0038] The beneficial effects produced by the above technical scheme are:

[0039] By using the similar material simulation test, the similar sample of the ore body can be determined through different material proportioning schemes and the pre-set similarity coefficient, and the three-dimensional model of the ore body is poured, so that the present application can adapt to the complex and variable surrounding rock conditions, and provide theoretical guidance for obtaining the supporting scheme, and then the supporting force of the jack structure is simulated to expand the supporting force of the expansion support, the supporting force of the jack and the vertical load of the loading system are adjusted, the roof characteristic curve of the supporting force and the roof displacement is drawn, and in the experimental process, the present application can control the test in the same stope, thereby reducing the material loss and reducing the influence of other factors on the results. At the same time, the technical scheme of the present application has high construction efficiency, compared with the field test method, the test period is short, and the result is more intuitive. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The present application is a kind of roof characteristic curve accurate determination method based on similar material test in the embodiment of the present application;

[0041] Figure 2 The test device schematic diagram in the embodiment of the present application, in the drawing, 1-loading system, 2-jack, 3-high-precision force sensor, 4-high-speed camera instrument, 5-VIC-3D speckle displacement monitoring system;

[0042] Figure 3 A physical model diagram of the jacking support in the embodiment of the present application;

[0043] Figure 4 A schematic diagram of the roof image in the embodiment of the present application;

[0044] Figure 5 A schematic diagram of the roof characteristic curve in the embodiment of the present application. DETAILED DESCRIPTION

[0045] The specific embodiments of the present application are described in further detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0046] The present application provides a kind of roof characteristic curve accurate determination method based on similar material test, specifically, the present application belongs to the key field of stability control to roof in underground mineral resources exploitation, especially related to a kind of accurate determination method of roof characteristic curve under the support condition of pre-stressed yielding bearing expansion prop.This field is crucial to guarantee the safe, efficient exploitation of underground mineral resources, and the roof characteristic curve determination method focused by the present application will provide more scientific, accurate basis for the stability control of underground stope roof.

[0047] In order to solve the many deficiencies of the existing roof characteristic curve determination method, meet the demand of accurate control of roof stability in underground mineral resources exploitation. Therefore, it is of urgent practical significance to develop a more scientific, accurate, reliable determination method of roof characteristic curve under the support condition of pre-stressed yielding bearing expansion prop.

[0048] The present application aims to overcome the deficiencies of the prior art in the determination of the roof characteristic curve of deep mining, and proposes a roof characteristic curve accurate determination method based on similar material test, which is used to study the mechanical characteristic curve behavior of the roof under the support of prestressed expansion support. The method proposed by the present application is suitable for obtaining the roof characteristic curve of various gently inclined ore body stope under support conditions, and the physical model simulates the target ore body stope and its surrounding rock system. The method relies on the similarity principle, and establishes a physical model according to the predetermined similarity ratio, and simulates the stope excavation process in the model. The test system mainly includes a similar material testing machine, a jack, a VIC-3D speckle displacement monitoring system and a stress sensor composed of similar material blocks and strain gauges. In order to ensure the consistency of the stope conditions, a single variable control method is used in the experiment process, and the jacks are arranged inside the stope. By adjusting the support force of the jacks, the different active support forces provided by the prestressed expansion support are simulated, and the stress sensor composed of similar material blocks and strain gauges is used to monitor the stress change of the roof. The VIC-3D system is used to monitor the displacement evolution process of the key area of the stope roof in real time, accurately quantify the maximum displacement of the roof under different support forces, and provide core data support for drawing the support force-displacement relationship curve (roof characteristic curve), and provide scientific basis for the stability analysis and support parameter optimization of deep mining roof.

[0049] Among them, the VIC-3D speckle displacement monitoring system is a non-contact optical measurement system based on digital image correlation method, which acquires high-resolution sequence images of model surface speckle field, combines image processing algorithm, and calculates full-field displacement field and strain field of model roof under load. The system includes the following three parts:

[0050] 1) High-speed camera instrument: synchronously acquires speckle image sequence of model surface at fixed frame rate;

[0051] 2) Image processing software: based on the preset speckle matching algorithm (such as sub-pixel interpolation algorithm), calculate the displacement vector of speckle points in adjacent images;

[0052] 3) Three-dimensional full-field reconstruction module: reconstruct the three-dimensional displacement field and strain field distribution of the model surface through the principle of double-camera stereo vision.

[0053] Based on this, the present application provides a roof characteristic curve accurate determination method based on similar material test, which combines Figure 1 , and can specifically include the following steps:

[0054] Step 1: determine the similarity coefficient between the ore body and the three-dimensional model of the ore body, the similarity coefficient includes the geometric similarity coefficient and the volume weight similarity coefficient;

[0055] Among them, the geometric similarity coefficient is expressed as:

[0056] ;

[0057] wherein, represents the length of the ore body, represents the length of the three-dimensional model of the ore body;

[0058] The smaller the geometric similarity ratio is, the larger the model is, and the more the model can reflect the actual engineering problems on site. However, due to the limitation of the size of the indoor similar test model, it is impossible to keep the similarity ratio to 1 with the site. In the actual test process, for the simulation of underground stope mining, the simulation similarity ratio coefficient C L Generally, 50-100 is taken, that is, the original stope is reduced by 50-100 times in length, width and height in proportion.

[0059] wherein, the bulk density similarity coefficient is represented as:

[0060] ;

[0061] wherein, represents the bulk density of the ore body, represents the bulk density of the three-dimensional model of the ore body.

[0062] wherein, the bulk density similarity coefficient may be selected between 1-2.

[0063] Step 2: according to a plurality of material proportioning schemes set in advance, a plurality of samples of the three-dimensional model of the ore body are prepared, a target sample is determined according to the similarity coefficient, and the three-dimensional model of the ore body is poured, the three-dimensional model of the ore body is a cuboid model;

[0064] wherein, the target sample is determined according to the similarity coefficient, and the three-dimensional model of the ore body is poured, comprising:

[0065] The bulk density similarity coefficient of each sample is calculated, the sample within the preset numerical range of the bulk density similarity coefficient is obtained as the target sample, and the three-dimensional model of the ore body is poured according to the geometric similarity coefficient and the material proportioning scheme of the target sample;

[0066] Specifically, the bulk density of the ore body and the preset numerical range of the bulk density similarity coefficient are obtained, the bulk density of the sample is measured, the ratio between the bulk density of the ore body and the bulk density of the sample is calculated, the bulk density similarity coefficient of the sample is obtained, and then the bulk density similarity coefficient of each sample is obtained, the sample within the preset numerical range of the bulk density similarity coefficient is obtained as the target sample from all the bulk density similarity coefficients of the samples, the length of the ore body and the preset geometric similarity coefficient are obtained, the length of the three-dimensional model of the ore body is calculated, and the three-dimensional model of the ore body is poured based on the length of the three-dimensional model of the ore body and the material proportioning scheme of the target sample.

[0067] That is, the application pre-provides a preset numerical range of the volume weight similarity coefficient and a specific value of the geometric similarity coefficient, and the actual length and the actual volume weight can be obtained according to the ore body measurement, so that the volume weight of the sample can be calculated according to the existing method after the sample is prepared, and then the volume weight of the ore body is divided by the volume weight of the sample to obtain the volume weight similarity coefficient of the sample, if the volume weight similarity coefficient of the sample is within the preset numerical range of the volume weight similarity coefficient, the sample is taken as the target sample, and then the length of the ore body three-dimensional model is calculated according to the specific value of the geometric similarity coefficient and the actual length obtained by the ore body measurement, and the ore body three-dimensional model is poured.

[0068] It should be noted that the geometric similarity coefficient in the application only mentions length, and further can also include specific dimensions of the ore body, such as width and height; if the volume weight similarity coefficients of the samples obtained by the plurality of material proportioning schemes pre-provided by the application are all not within the preset numerical range of the volume weight similarity coefficient, the material proportioning scheme can be re-set, and further, the new material proportioning scheme can be obtained by adjusting the material proportioning scheme closest to the preset numerical range of the volume weight similarity coefficient to prepare the sample again.

[0069] Step 3: curing and surface treatment are performed on the ore body three-dimensional model to obtain a treated ore body three-dimensional model;

[0070] Specifically, the curing is natural curing, the ore body three-dimensional model is covered with a plastic film, and water is sprayed to keep the ore body three-dimensional model wet, wherein the temperature of the curing environment should be kept at 20±2℃, and the humidity should be above 95%. The core purpose is to maintain the stability of the material physical and mechanical parameters and the design similarity ratio, to ensure that the model accurately simulates the prototype behavior within the test period, after the curing is completed, the baffle is removed and continues to be stationary, after the cured ore body three-dimensional model is dried, a layer of white paint is uniformly sprayed on the surface of the ore body three-dimensional model, and after the white paint is dried, black speckles are sprayed again to obtain the treated ore body three-dimensional model.

[0071] The diameter of the black speckles can be set according to the actual situation, and the black speckles with a diameter of about 5 mm can be used in the application, and the black speckles are used to form a speckle field suitable for VIC-3D system identification.

[0072] Step 4: according to the size and position of the stope area pre-designed, the treated ore body three-dimensional model is excavated to obtain a ore body three-dimensional model after stope excavation;

[0073] The stope area penetrates two parallel planes of the treated ore body three-dimensional model, and the ore body three-dimensional model after stope excavation generates four planes in the stope area.

[0074] Step 5: Place the jack in the stope area, place the high-precision force sensor under the jack, place the existing loading system above the stope area, on the outer surface of the ore body three-dimensional model after the stope excavation, such as Figure 2 Wherein, 1 is the loading system, 2 is the jack, 3 is the high-precision force sensor, 4 is the high-speed camera instrument, and 5 is the VIC-3D speckle displacement monitoring system.

[0075] Wherein, the jack is used to apply support force above the stope area, and the loading system is used to apply vertical load above the stope area, wherein the plane directly contacted by the jack to apply support force is the roof;

[0076] It should be noted that the number of jacks can be set according to actual conditions, and when the number of jacks is multiple, the support force is the sum of the support forces of all jacks, for example, when the number of jacks is 3 and the support force is 900, the support force of each jack is 300.

[0077] Specifically, the jack is placed on the first plane in the ore body three-dimensional model after the stope excavation, the first plane is any of the four planes generated by the stope area, and the steel plate and the high-precision force sensor are sequentially arranged between the first plane and the jack, the other end of the jack is in contact with the second plane, the second plane is a plane parallel to the first plane among the four planes generated by the stope area, the second plane is the roof, and the other end of the jack is in contact with the second plane. A steel plate is arranged between the other end of the jack and the second plane, and an existing loading system is arranged on the target plane of the ore body three-dimensional model after the stope excavation, the target plane is the plane parallel to the second plane and closest to the second plane among the external planes of the ore body three-dimensional model after the stope excavation.

[0078] Wherein, the function of the steel plate is to ensure uniform transmission of vertical load and support force.

[0079] Step 6: Increase the vertical load by the loading system and increase the support force by the jack according to the preset gradient, specifically, the stress gradient can be gradually increased by 0.05 MPa, the support force is collected and monitored in real time by the high-precision force sensor, so that the support force and the vertical load are equal in size, until the support force and the vertical load reach the original rock stress;

[0080] It should be noted that, in combination with Figure 3 The upward arrow is the support force applied by the jack to the roof, according to Newton's third law, the support force applied by the jack to the roof is equal in size and opposite in direction to the reaction force suffered by the high-precision force sensor. The high-precision force sensor converts the mechanical signal into an electrical signal, which is transmitted in real time to the control console by the dynamic acquisition system (sampling frequency ≥ 100 Hz), realizing closed-loop monitoring of the support force.

[0081] Therefore, the original rock stress environment after excavation is accurately reconstructed, and uniform initial support force is established, so that the method can be universally applied to simulate the roof mechanical behavior of gently inclined ore body stope under different geological conditions, and then the characteristic curve is obtained.

[0082] The original rock stress is calculated by the following method:

[0083] The self-weight stress q of the ore body is calculated p , and is realized by the following formula:

[0084] q p = γ p H ;

[0085] Wherein, The bulk density of the ore body is denoted by H, and the actual stope depth of the ore body is denoted by H.

[0086] According to the similarity criterion, the similarity ratio of stress, strength, elastic modulus, cohesion and other parameters in the similar test is the product of the geometric similarity ratio and the bulk density similarity ratio, so the geometric similarity coefficient and the bulk density similarity coefficient are multiplied to obtain the stress similarity coefficient, and the self-weight stress of the ore body is multiplied by the stress similarity coefficient to obtain the original rock stress.

[0087] Step 7: gradually reduce the support force of the jack according to the preset gradient, calculate the maximum displacement of the roof, and generate the curve of support force and maximum displacement, that is, the roof characteristic curve.

[0088] Gradually reduce the support force of the jack according to the preset gradient until the roof is damaged or the support force is reduced to 0. Specifically, the reduction of the support force can be realized by the following formula:

[0089] Pi=β•P0;

[0090] Wherein, P0 is the current support force, Pi represents the reduced support force, and β is the attenuation coefficient, β≤1.

[0091] The support force is collected and monitored in real time by a high-precision force sensor, the roof image is collected in real time by a high-speed camera instrument in the VIC-3D speckle displacement monitoring system, such as Figure 4 The VIC-3D software (i.e. image processing software) in the VIC-3D speckle displacement monitoring system is used to process the roof image, so as to obtain the maximum displacement of the roof corresponding to each support force, and generate the curve of support force and maximum displacement, that is, the roof characteristic curve, such as Figure 5 Wherein, the fitting curve is the roof characteristic curve.

[0092] In the implementation process, two or more high-resolution industrial cameras (≥ 500 million pixels) are synchronously erected to cover the monitoring area at an angle of 30°-60°, and controllable LED light sources are used to eliminate environmental interference. Precise chessboard calibration plates are used for stereo calibration to ensure that the reprojection error is ≤ 0.02 pixels. During the experiment, when a specific support force Pi is applied, the synchronous controller triggers the camera to collect speckle images at an interval of 0.1 seconds, which are transmitted to the VIC-3D software in real time. Based on the VIC-3D software, the global three-dimensional displacement field of the roof can be output. The displacement field is first subjected to 3x3 median filtering to eliminate noise, and the high-risk area of the roof (such as the midspan position) is framed in the software. The displacement vector [Ux, Uy, Uz] of all nodes is traversed, and the combined displacement modulus is calculated. The maximum value and its spatial coordinates are recorded in real time. This process is repeated under each support force Pi, and finally a data table containing the support force, maximum displacement, occurrence position, and timestamp is formed. After the error verified by the laser interferometer is < ± 0.01 mm, the support force-displacement characteristic curve (i.e., the roof characteristic curve) can be drawn.

[0093] The above description is only the preferred embodiments of the present disclosure and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the above features can be replaced with the technical features disclosed in the embodiments of the present disclosure (but not limited to) having similar functions to form technical solutions.

Claims

1. A method for accurately determining the top plate characteristic curve based on similar material tests, characterized in that, include: Step 1: Determine the similarity coefficient between the ore body and its 3D model, including the geometric similarity coefficient and the bulk density similarity coefficient; Step 2: Based on multiple pre-set material ratio schemes, prepare multiple samples of the three-dimensional model of the ore body. Determine the target sample based on the similarity coefficient and cast the three-dimensional model of the ore body. The three-dimensional model of the ore body is a cuboid model. Step 3: Curing and surface treatment of the ore body 3D model to obtain the treated ore body 3D model; Step 4: Based on the pre-designed size and location of the mining area, create a three-dimensional model of the ore body after excavation. The mining area penetrates two parallel planes of the processed ore body 3D model, and the ore body 3D model after mining excavation generates four planes in the mining area. Step 5: Place jacks in the mining area, place high-precision force sensors below the jacks, and place the existing loading system on the outer surface of the 3D model of the ore body after mining excavation above the mining area. The jack is used to apply support force to the area above the mining area, and the loading system is used to apply vertical load to the area above the mining area. The plane in which the jack directly contacts the surface to apply support force is the roof. Step 6: According to the preset gradient, increase the vertical load through the loading system, increase the support force through the jacks, and collect and monitor the support force in real time through the high-precision force sensor to make the support force and the vertical load equal until the support force and the vertical load reach the original rock stress. Step 7: Gradually reduce the support force of the jacks according to the preset gradient, calculate the maximum displacement of the roof, and generate the curve of support force and maximum displacement, i.e., the roof characteristic curve.

2. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, The geometric similarity coefficient Represented as: ； in, Indicates the length of the ore body. Indicates the length of the 3D model of the ore body; Wherein, the bulk density similarity coefficient Represented as: ； in, Indicates the bulk density of the ore body. This indicates the bulk density of the ore body in a three-dimensional model.

3. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, Step 2 involves determining the target sample based on the similarity coefficient and casting a three-dimensional model of the ore body, including: Calculate the bulk density similarity coefficient for each sample, obtain samples within the preset range of bulk density similarity coefficient as target samples, and cast a three-dimensional model of the ore body according to the geometric similarity coefficient and the material ratio scheme of the target samples. Specifically, the pre-defined range of the bulk density and bulk density similarity coefficient of the ore body is obtained, the bulk density of the sample is measured, the ratio between the bulk density of the ore body and the bulk density of the sample is calculated, the bulk density similarity coefficient of the sample is obtained, and then the bulk density similarity coefficient of each sample is obtained. Among all the bulk density similarity coefficients of the samples, the sample within the pre-defined range of the bulk density similarity coefficient is selected as the target sample. The length of the ore body and the pre-defined geometric similarity coefficient are obtained, the length of the 3D model of the ore body is calculated, and the 3D model of the ore body is cast based on the length of the 3D model of the ore body and the material ratio scheme of the target sample.

4. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, Step 3 specifically includes: The 3D model of the ore body is covered with plastic film and kept moist by sprinkling water. After the 3D model of the ore body dries, a layer of white paint is evenly sprayed on the surface of the 3D model of the ore body. After the white paint dries, black speckled paint is sprayed on to obtain the processed 3D model of the ore body.

5. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, Step 5 specifically includes: A jack is placed on the first plane within the three-dimensional model of the ore body after the mining area is excavated. The first plane is any one of the four planes generated in the mining area. A steel plate and a high-precision force sensor are sequentially arranged between the first plane and the jack. The other end of the jack is in contact with the second plane. The second plane is the plane parallel to the first plane among the four planes generated in the mining area. The second plane is the roof plate. A steel plate is arranged between the other end of the jack and the second plane. An existing loading system is set on the target plane of the three-dimensional model of the ore body after the mining area is excavated. The target plane is the plane that is parallel to the second plane and closest to the second plane among the outer planes of the three-dimensional model of the ore body after the mining area is excavated.

6. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, Step 7 specifically includes: The support force of the jacks is gradually reduced according to a preset gradient until the roof is damaged or the support force is reduced to 0. The support force is collected and monitored in real time by a high-precision force sensor. The roof image is collected in real time by a high-speed camera in the VIC-3D speckle displacement monitoring system. The roof image is processed by the VIC-3D software in the VIC-3D speckle displacement monitoring system to obtain the maximum displacement of the roof corresponding to each support force, and generate a curve of support force and maximum displacement, i.e., the roof characteristic curve.

7. The method for accurately determining the top plate characteristic curve based on similar material testing according to claim 1, characterized in that, The original rock stress is calculated in the following way: Calculate the self-weight stress q of the ore body p Specifically, this is achieved through the following formula: q p = γ p H ; in, H represents the unit weight of the ore body, and H represents the actual burial depth of the ore body in the mining area. Multiplying the geometric similarity coefficient and the unit weight similarity coefficient yields the stress similarity coefficient. Multiplying the self-weight stress of the ore body by the stress similarity coefficient yields the original rock stress.

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