Refined identification of large-scale rock mass structure and acquisition method of size effect parameters

Abstract

The present invention relates to a method for fine identification of large-scale rock mass structure and acquisition of size effect parameters, which is applicable to the field of engineering rock mass technology. The technical scheme adopted by the present invention is: collecting and counting structural surface information of natural rock mass; generating a three-dimensional synthetic rock mass structural surface network model based on the structural surface information of natural rock mass; obtaining mechanical parameters of natural rock mass; distributing rock mass particles in the three-dimensional synthetic rock mass structural surface network model based on the three-dimensional synthetic rock mass structural surface network model and the mechanical parameters of natural rock mass to form a three-dimensional synthetic rock mass numerical model; obtaining a plurality of natural rock mass samples of different sizes and different positions from the natural rock mass, and obtaining the peak strength and failure characteristics of the natural rock mass samples; obtaining a plurality of numerical model samples corresponding to the natural rock mass samples one by one from the three-dimensional synthetic rock mass numerical model, and obtaining the peak strength and failure characteristics of the numerical model samples.

Description

Technical Field

[0001] The present invention relates to a method for fine identification of large-scale rock mass structure and acquisition of size effect parameters, which is applicable to the technical field of engineering rock mass. Background Art

[0002] Rock mass structure is the main basis for geological evaluation. Rock mass is composed of two basic units: geological interface and rock blocks surrounded by geological interface, namely structural surface and structure. And the deformation and failure of rock mass are also controlled by rock material and structural surface. Structural surface is the main factor that constitutes rock mass structure and controls rock mass mechanical properties. Therefore, only by obtaining complete structural surface information, such as spatial distribution characteristics, can a more accurate evaluation of rock mass engineering geological characteristics be provided.

[0003] For engineering rock mass, it is necessary to carry out engineering design and formulate corresponding safety measures based on the rock mass structural surface information such as joints, crack positions, etc. and their mechanical properties. For rock masses of different scales, the number and position of internal joints and cracks are very different, so the mechanical properties of rock masses of different scales are also quite different. In engineering, natural rock masses are often subjected to field and indoor mechanical tests to evaluate the rock mass performance. However, for indoor tests on natural rock masses, due to the specifications of the test instruments and the test time, it is often impossible to conduct mechanical tests on the complete rock mass. Only test cores can be taken from the natural rock mass for mechanical property testing. Through structural tests on rock masses, it is found that to a certain extent, the test results are affected by the size. Therefore, the study of the size effect of rock masses is very important for the prediction of the mechanical properties of large-scale rock masses and has important practical significance.

[0004] For the current rock engineering excavation, the mechanical properties of natural rock cannot be accurately obtained, resulting in improper selection of parameters for caverns, dams and slopes. During excavation, load changes occur near the excavation surface, causing stress redistribution, which in turn causes rock deformation to develop rapidly on certain structural surfaces or weak parts, resulting in fractures and new through-slips, leading to instability and damage of rock engineering, such as dam breaches, cavern collapses, slope instability, etc. Therefore, it is necessary to measure, analyze and summarize the structural surfaces through certain methods, find out the distribution rules, surface characteristics and spatial combinations, and then determine the stability conditions and stability of the rock mass.

[0005] Over the years, through a large number of research experiments, great achievements have been made in the acquisition of rock mass structural surface information, and many rock mass structural surface information acquisition methods have been proposed, such as drilling core joint acquisition method, line survey method, photogrammetry method, etc. However, for large-scale rock mass structural surface information acquisition, geological compass is still the main method, which cannot quickly and comprehensively collect rock mass structural information. In addition, for large-scale rock mass, its size effect also has three classic problems, such as long and weak structural surface, discrete fracture network and anisotropic rock mass, which leads to inaccuracy in the obtained rock mass mechanical properties and their related change laws. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a method for fine identification of large-scale rock mass structure and acquisition of size effect parameters is provided.

[0007] The technical solution adopted by the present invention is: a method for fine identification of large-scale rock mass structure and acquisition of size effect parameters, characterized in that:

[0008] Collect and count the structural surface information of natural rock mass;

[0009] Generate a three-dimensional synthetic rock mass structural surface network model based on the structural surface information of natural rock mass;

[0010] Obtain mechanical parameters of natural rock mass;

[0011] Based on the three-dimensional synthetic rock mass structural surface network model and the mechanical parameters of the natural rock mass, the rock mass particles are distributed in the three-dimensional synthetic rock mass structural surface network model to form a three-dimensional synthetic rock mass numerical model;

[0012] Obtain multiple natural rock samples of different sizes and positions from the natural rock mass to obtain the peak strength and failure characteristics of the natural rock samples; obtain multiple numerical model samples corresponding to the natural rock samples from the three-dimensional synthetic rock mass numerical model to obtain the peak strength and failure characteristics of the numerical model samples, and adjust the mechanical parameters of the three-dimensional synthetic rock mass model based on the comparative analysis of the peak strength and failure characteristics of the natural rock mass samples and the numerical model samples;

[0013] Cut and generate rock model specimens of different sizes in the adjusted and corrected three-dimensional synthetic rock mass numerical model to obtain their relevant mechanical properties;

[0014] The stress-strain curve is drawn on the same graph according to the relevant mechanical properties of rock model specimens of different sizes. The size effect of the rock model is obtained according to the characteristics of stress-strain variation with age.

[0015] The collecting and counting of structural surface information of natural rock mass includes: obtaining a large number of geological pictures of natural rock mass slopes.

[0016] The method of generating a three-dimensional synthetic rock mass structural surface network model of a natural rock mass based on the structural surface information of the natural rock mass comprises:

[0017] Generate point cloud data based on geological pictures of natural rock slopes, and reconstruct a three-dimensional digital terrain model of natural rock slopes using point cloud data;

[0018] According to the three-dimensional coordinates on the natural rock structure surface, the structural surface is interpreted;

[0019] Generate a three-dimensional structural surface network based on the location and size of the structural surface on the three-dimensional digital terrain model;

[0020] A three-dimensional space is established, and the generated three-dimensional structural surface network is cut with it to obtain a three-dimensional synthetic rock mass structural surface network model of the rock mass area corresponding to the three-dimensional space.

[0021] The method of generating a three-dimensional structural surface network based on the position and size of the structural surface on the three-dimensional digital terrain model includes:

[0022] Draw the iso-density lines of the structural surface poles based on the natural rock mass structural surface data;

[0023] The density and position of the structural surface are simulated according to the isovalue density lines of the structural surface poles, and a three-dimensional structural surface network with a thin disk shape is randomly generated through the Monte Carlo simulation method.

[0024] Based on the 3D synthetic rock mass structural surface network model and the mechanical parameters of the natural rock mass, the rock mass particles are distributed in the 3D synthetic rock mass structural surface network model to form a 3D synthetic rock mass numerical model, including:

[0025] The rock mass particles are randomly distributed in the three-dimensional synthetic rock mass structural surface network model to form a three-dimensional synthetic rock mass numerical model;

[0026] The three-dimensional synthetic rock mass numerical model is adjusted and set according to the mechanical parameters of the natural rock mass.

[0027] Rock mass model specimens of different sizes are cut from the adjusted and calibrated three-dimensional synthetic rock mass numerical model to obtain their relevant mechanical properties, including:

[0028] Numerical tests are carried out on rock model specimens of the same center and different scales to obtain their relevant mechanical properties;

[0029] Numerical tests are carried out on rock model specimens with different centers and the same scale to obtain their relevant mechanical properties;

[0030] Particle flow slicing was performed on rock model specimens of different scales and numerical experiments were carried out to obtain their relevant mechanical properties.

[0031] The beneficial effects of the present invention are as follows: by collecting the on-site digital photography of the natural rock mass structure surface, on the basis of the structure surface information collection and statistics, a digital terrain model of the representative area is generated, and a trace diagram is drawn according to the coordinates of the extreme end points of the fracture. According to the measured parameters such as the shape, occurrence, spacing of the structure surface and the size of the structure surface inferred from the measurement window trace diagram, a three-dimensional synthetic rock mass structure surface network of the representative area is generated through the Poisson process. Then, the mechanical parameters of the natural rock mass and the structure surface are determined through indoor tests and field tests. On this basis, the three-dimensional synthetic network model is randomly filled with particles and relevant parameters are set to generate a three-dimensional synthetic rock mass numerical model. Further, a numerical simulation test of specific mechanical boundary conditions is carried out on the numerical model, and the boundary conditions are consistent with those of the indoor test. The test results and failure characteristics of the two are analyzed and compared, so as to correct the three-dimensional synthetic rock mass parameters and obtain a true simulation of the natural rock mass. For the generated three-dimensional synthetic rock mass model, mechanical performance tests and failure characteristics of particle flows of different scales, different centers of the same scale, and different scales can be carried out to obtain the high-precision size effect change characteristics of the rock mass. It solves the difficulty of accurate quantitative evaluation of large-scale rock mass performance, improves the speed and accuracy of large-scale rock mass structural surface information collection, and provides a reference for related engineering design and stability evaluation of large-scale rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 , 2 A schematic diagram of the process of fine identification technology of large-scale rock structure and acquisition of size effect parameters provided in an embodiment of the present invention.

[0033] Figure 3 The present invention provides a natural rock structure surface digital acquisition process.

[0034] Figure 4 A three-dimensional rock model synthesis process is provided in an embodiment of the present invention.

[0035] Figure 5 An on-site shear test device is provided in an embodiment of the present invention.

[0036] Figure 6 Rock mass models of different scales provided by the embodiments of the present invention.

[0037] Figure 7 The same scale, different center model provided for the embodiment of the present invention.

[0038] Figure 8 Particle flow models of different scales provided by the embodiments of the present invention.

[0039] Fig. 9 Numerical experiment curve diagram of different scale models provided by the embodiments of the present invention. DETAILED DESCRIPTION

[0040] like Figure 1 , 2 As shown, the method for fine identification of large-scale rock mass structure and acquisition of size effect parameters provided in this embodiment includes the following steps:

[0041] Step 101, natural rock mass structural surface information collection and information statistics.

[0042] In order to obtain the address image of the natural rock slope, multi-station frontal photography of the high slope facade was carried out through digital acquisition. According to the actual situation on site, cameras were used to carry out multi-station photography of different elevation surfaces and multiple base stations. Each station shooting needed to have a 66 degree of overlap, and the slope should be photographed as much as possible from different photography surfaces to avoid photography blind spots.

[0043] Step 102, generating a three-dimensional structural surface network of the natural rock mass to obtain a fracture network.

[0044] After the photography field work, the pictures with different focal lengths are classified and processed and imported into the software; then, the multi-view Figure 3 3D reconstruction technology automatically calculates the photo position, automatically orients and generates point cloud data based on the impact, POS data and ground point control point data; extracts point cloud data with coordinate information from the captured pictures based on the image scanning system, and quickly reconstructs the 3D digital terrain model of the natural rock mass;

[0045] The three-dimensional coordinates of points on the structural surface can be used to interpret the structural surface. Geometric interpretation, simulation interpretation and three-point interpretation can be used. As for the size of the structural surface, it can be concluded that it is related to the trace length through correlation analysis. Therefore, through the digital terrain model, the coordinates of the extreme end points of the fracture and the coordinates of the characteristic points on the fracture surface that characterize the rock mass occurrence are collected, the trace diagram is drawn, and the trace length is measured to determine the size of the structural surface (for specific procedures, refer to Figure 3 ).

[0046] Based on the field measurements and image data, the rock mass random structural surface dominant groups are divided according to the structural surface shape, occurrence, spacing, etc. The division results are expressed by the strike rose diagram expressed by the right-hand rule;

[0047] The natural structural surface data are collected through precise measurement by the line survey method, and the obtained data are sorted to draw the iso-density lines of the structural surface poles; the Poisson process is applied to simulate the density and position of the structural surface according to the iso-density lines of the structural surface poles; and the Monte Carlo simulation method is used to randomly generate a three-dimensional structural surface network with the structural surface in the shape of a thin disk.

[0048] According to the actual size of natural rock mass and the subsequent study on the size effect of natural rock mass, a three-dimensional space of 60m×60m×60m was established, and the generated three-dimensional structural surface network was cut with it, and finally a representative three-dimensional synthetic rock mass structural surface network model of the area was obtained (reference Figure 4 ).

[0049] Step 103, conducting indoor and field experiments on natural rock mass to obtain mechanical parameters.

[0050] Conduct on-site physical property tests on natural rock mass to obtain physical properties such as density and hardness of natural rock mass. Based on the determined sample size, use the mass volume method to measure the density of the sample.

[0051] Conduct on-site shear tests on natural rock mass, select representative rock mass, and prepare test samples that meet the test requirements by artificially excavating or carving in the original rock mass. Five points are grouped together to eliminate the impact of human disturbance on rock mass performance. The overall test process meets the relevant requirements of the "Standard for Engineering Geotechnical Test Methods". The test pit is excavated by a cutting machine to minimize disturbance to the rock mass. A saturated water test is carried out after excavation to ensure that the rock mass is in a saturated state. The size of the on-site pressure plate is 50cm×50cm, and the size of the exposed original rock is 50cm×50cm×30cm. A horizontal jack is used to apply horizontal force to the original rock. The test device is referenced Figure 5 , and then obtain the shear mechanical properties and related mechanical parameters of natural rock mass;

[0052] Core samples are taken from representative areas of natural rock mass for indoor mechanical experiments, including shear tests and triaxial compression tests. The standards of the samples should meet the requirements of shear equipment and compression equipment. The size of the sample used in this test is 100mm×100mm×100mm. The shear test equipment uses a YZW50 electric stress shear instrument to obtain the shear mechanical performance parameters and failure characteristics of the rock mass sample. The sample is subjected to a triaxial compression test, in which the confining pressure of the sample should be the same as the ground stress of the natural rock mass. The compressive strength, natural stress parameters and failure characteristics of the rock are obtained through triaxial testing;

[0053] Due to the uniqueness of natural rock samples, when the shear deformation increases sharply or reaches 1 / 10 of the sample size, the test is terminated to facilitate repeated testing.

[0054] Step 104: Generate a three-dimensional synthetic rock mass numerical model.

[0055] The structure is composed of structural surfaces and rock mass. Therefore, based on the obtained three-dimensional structural surface network model, the rock mass particles are randomly distributed in the three-dimensional structural surface network model through software simulation to form a three-dimensional synthetic rock mass numerical model.

[0056] According to the mechanical parameters of natural rock mass such as density, compression resistance and shear resistance measured in indoor and field tests, the three-dimensional synthetic rock mass numerical model is set to obtain a complete natural rock mass numerical model.

[0057] Step 105, complete the real simulation of the failure mechanism of the synthetic rock mass from local to overall.

[0058] Select natural rock samples of different sizes and locations. The size requirements should meet the size requirements of indoor test equipment, and consider the test time factor, and select the sample size with a side length of less than 100mm. At the same time, mark the sampling location.

[0059] The cutting position on the three-dimensional synthetic rock mass numerical model is determined by the marked position, and a numerical model sample is cut to correspond one to one with the natural rock mass sample (with the same position and size).

[0060] Triaxial compression test and shear test were carried out on natural rock samples to obtain their peak strength and failure characteristics. At the same time, numerical tests with specific mechanical boundary conditions were carried out on numerical model samples of the same size. The boundary condition parameters were kept consistent with those in the indoor tests to obtain their peak strength and failure characteristics.

[0061] The test results of the indoor test and the numerical test are compared and analyzed, and the mechanical parameter settings of the three-dimensional synthetic rock mass are adjusted according to the comparison and analysis results, so as to ensure that the numerical model can simulate the natural rock mass most realistically.

[0062] This embodiment conducts numerical tests from local to overall on a numerical model with calibrated parameters, analyzes its failure mechanism, and thus completes a true simulation of large-scale natural rock mass failure.

[0063] Step 106, conducting mechanical property tests of rock masses at different scales.

[0064] In the calibrated three-dimensional synthetic rock mass numerical model, the model size required for the numerical model test is cut to obtain rock mass model specimens. The rock mass model specimens are all square, with sizes of 1m, 2m, 4m, 5m, 8m, 10m, 20m, 40m, 50m, and 60m. Numerical tests with specific boundary conditions are carried out on them, and the relevant mechanical properties are analyzed.

[0065] Numerical tests were conducted on three-dimensional synthetic rock models of the same center and different scales to obtain their relevant mechanical properties. Figure 6 ;

[0066] Numerical tests were conducted on three-dimensional synthetic rock models with different centers and the same scale to obtain their relevant mechanical properties. Figure 7 ;

[0067] The particle flow slices were sliced ​​and numerical experiments were performed on the three-dimensional synthetic rock models of different scales to obtain their relevant mechanical properties. Figure 8 .

[0068] Step 107, obtaining high-precision size effect variation characteristics of the synthetic rock mass.

[0069] By conducting numerical tests on rock mass model specimens of different scales, the stress, strain, displacement and other data corresponding to the models of different sizes are obtained, and the corresponding graphs are drawn. The stress-strain curves under the numerical models of different scales are drawn in a graph, as shown in the figure. Fig. 9 , analyze the characteristics of stress and strain changes with size, and obtain the size effect of the three-dimensional rock model, so as to accurately predict the mechanical properties of large-scale natural rock masses.

[0070] This embodiment generates a three-dimensional structural surface network of the natural rock mass in the representative area and obtains a discrete fracture network based on the analysis and statistics of the natural rock mass structural surface information by digitally collecting large-scale natural rock mass information; then, the relevant mechanical parameters of the rock and structural surface are obtained by conducting field experiments on complete rock samples and indoor tests on the rock mass structural surface. Furthermore, based on the generation of the three-dimensional structural surface network and the acquisition of the mechanical parameters of the rock and structural surface, a large-scale three-dimensional synthetic rock mass numerical model is generated. On this basis, a sample consistent with the indoor test scale is selected, and numerical tests under specific mechanical boundary conditions and indoor mechanical tests of natural rock mass under this scale are carried out to obtain the mechanical properties and failure characteristics of the three-dimensional synthetic rock mass and natural rock mass, and analyze and compare them. According to the comparison results, the mechanical parameter selection of the three-dimensional numerical model is corrected; then, simulations of three-dimensional numerical models of different scales under different mechanical boundary conditions are carried out to obtain the mechanical properties and failure characteristics of three-dimensional models of different scales, and obtain the high-precision size effect change characteristics of the rock mass, which solves the problem that the mechanical properties of natural large-scale rock mass cannot be quantitatively evaluated in the past, and the geological characteristics of the natural large-scale rock mass structural surface can be obtained efficiently and quickly. Therefore, this embodiment can improve the understanding of the mechanical properties and failure laws of large-scale natural rock structure surfaces, and provide a reference for the design and safety and stability evaluation of rock engineering projects.

[0071] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the claims above.

[0072] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for fine identification of large-scale rock mass structure and acquisition of size effect parameters, characterized by: Collect and count the structural surface information of natural rock mass; Generate a three-dimensional synthetic rock mass structural surface network model based on the structural surface information of natural rock mass; Obtain mechanical parameters of natural rock mass; Based on the three-dimensional synthetic rock mass structural surface network model and the mechanical parameters of the natural rock mass, the rock mass particles are distributed in the three-dimensional synthetic rock mass structural surface network model to form a three-dimensional synthetic rock mass numerical model; Obtain multiple natural rock samples of different sizes and positions from the natural rock mass to obtain the peak strength and failure characteristics of the natural rock samples; obtain multiple numerical model samples corresponding to the natural rock samples from the three-dimensional synthetic rock mass numerical model to obtain the peak strength and failure characteristics of the numerical model samples, and adjust the mechanical parameters of the three-dimensional synthetic rock mass model based on the comparative analysis of the peak strength and failure characteristics of the natural rock mass samples and the numerical model samples; Cut and generate rock model specimens of different sizes in the adjusted and corrected three-dimensional synthetic rock mass numerical model to obtain their relevant mechanical properties; The stress-strain curve is drawn on the same graph according to the relevant mechanical properties of rock model specimens of different sizes. The size effect of the rock model is obtained according to the characteristics of stress-strain variation with age.

2. The method for fine identification of large-scale rock mass structure and acquisition of size effect parameters according to claim 1 is characterized in that: The collecting and counting of structural surface information of natural rock mass includes: obtaining a large number of geological pictures of natural rock mass slopes.

3. The method for fine identification of large-scale rock mass structure and acquisition of size effect parameters according to claim 2 is characterized in that: The method of generating a three-dimensional synthetic rock mass structural surface network model of a natural rock mass based on the structural surface information of the natural rock mass comprises: Generate point cloud data based on geological pictures of natural rock slopes, and reconstruct a three-dimensional digital terrain model of natural rock slopes using point cloud data; According to the three-dimensional coordinates on the natural rock structure surface, the structural surface is interpreted; Generate a three-dimensional structural surface network based on the location and size of the structural surface on the three-dimensional digital terrain model; A three-dimensional space is established, and the generated three-dimensional structural surface network is cut with it to obtain a three-dimensional synthetic rock mass structural surface network model of the rock mass area corresponding to the three-dimensional space.

4. The method for fine identification of large-scale rock mass structure and acquisition of size effect parameters according to claim 3 is characterized in that: The method of generating a three-dimensional structural surface network based on the position and size of the structural surface on the three-dimensional digital terrain model includes: Draw the iso-density lines of the structural surface poles based on the natural rock mass structural surface data; The density and position of the structural surface are simulated according to the isovalue density lines of the structural surface poles, and a three-dimensional structural surface network with a thin disk shape is randomly generated through the Monte Carlo simulation method.

5. The method for fine identification of large-scale rock mass structure and acquisition of size effect parameters according to claim 1, characterized in that: Based on the 3D synthetic rock mass structural surface network model and the mechanical parameters of the natural rock mass, the rock mass particles are distributed in the 3D synthetic rock mass structural surface network model to form a 3D synthetic rock mass numerical model, including: The rock mass particles are randomly distributed in the three-dimensional synthetic rock mass structural surface network model to form a three-dimensional synthetic rock mass numerical model; The three-dimensional synthetic rock mass numerical model is adjusted and set according to the mechanical parameters of the natural rock mass.

6. The method for fine identification of large-scale rock mass structure and acquisition of size effect parameters according to claim 1, characterized in that: Rock mass model specimens of different sizes are cut from the adjusted and calibrated three-dimensional synthetic rock mass numerical model to obtain their relevant mechanical properties, including: Numerical tests are carried out on rock model specimens of the same center and different scales to obtain their relevant mechanical properties; Numerical tests are carried out on rock model specimens with different centers and the same scale to obtain their relevant mechanical properties; Particle flow slicing was performed on rock model specimens of different scales and numerical experiments were carried out to obtain their relevant mechanical properties.

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