CN105973706B - Coal rock mass multi-scale mechanical property analysis method based on industrial CT - Google Patents
Coal rock mass multi-scale mechanical property analysis method based on industrial CT Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0284—Bulk material, e.g. powders
Abstract
A coal-rock multi-scale mechanical characteristic analysis method based on industrial CT is a coal-rock multi-scale mechanical characteristic analysis method capable of being matched with CT scanning characteristics, and comprises a whole set of methods of sequential cutting, CT accurate scanning, matrix inclusion remodeling, mechanical parameters obtained through respective three-axis experiments, and numerical compression by sequential combination to realize coal-rock multi-scale mechanical characteristic analysis, and breaks through the limitation of a traditional random simulation method based on probability statistics.
Description
Technical Field
The invention belongs to the field of rock mechanics, in particular to a multi-scale analysis method of a coal-rock mass, which is a supplement to a common multi-scale analysis method of the coal-rock mass and is particularly suitable for a multi-scale analysis method of a porous medium.
Background
The multi-scale analysis of the coal rock mass is carried out, and the understanding of the composition of the internal structure is the basis. In the existing coal rock mass multi-scale analysis method, in order to obtain the internal structure composition of the coal rock mass, an internal structure surface network is often constructed firstly. Firstly, carrying out probability statistical analysis and deviation correction on the inclination, inclination angle, spacing and track length of joints through field joint geological survey; then, according to the corrected data, a joint network is constructed by adopting a random simulation theory; and finally, comparing the joint network data with the joint deviation correction data, and verifying the statistical similarity of the joint network data and the joint deviation correction data.
It can be seen that the above-mentioned internal structure composition is obtained mainly based on statistics, which has the advantage that the whole can be replaced by a part, but has the disadvantage that the obtained internal structure has only statistical significance, the internal real situation is difficult to verify, and the result obtained by the method is difficult to judge whether the internal structure is correct or not.
The coal rock mass often has obvious heterogeneity, even if the coal rock mass is close to the geography, the coal rock mass can be influenced by factors such as stress, structure and the like, and has obvious variation characteristics, at the moment, the traditional multi-scale analysis method based on statistics often cannot be used for the variation analysis, and the method is a dilemma of the multi-scale research of the existing rock mass mechanics. The physical properties of the coal body are greatly influenced by the pores and inclusions which are different in size and uneven in distribution in the coal rock body, so that great errors are brought to the analysis result.
Therefore, there is a need for a multiscale analysis method based on the accurate analysis of internal structural features of coal and rock mass, which requires a CT scanning technique that can reproduce the true structure of the interior of the coal mass, and which is characterized by lossless quantitative refinement, to solve this problem well. Therefore, the invention constructs a novel coal-rock mass multi-scale mechanical property analysis method matched with the CT scanning characteristics on the basis of the microscopic characteristics obtained by scanning the coal sample by the industrial CT.
Based on the thought, the coal-rock mass multi-scale mechanical property analysis method based on the industrial CT is designed.
Disclosure of Invention
The method comprises the steps of firstly selecting blocks in an exploitation mine to be cut into cubes with the size of 1m × 1m × 1m, then cutting the cubes into 1000 small coal blocks with the size of 0.1m × 0.1.1 m × 0.1.1 m again, sequentially numbering and scanning by CT, sequentially recombining again to obtain a large cube grid model, grinding the cut coal blocks into coal powder, remolding, respectively carrying out a triaxial experiment to obtain mechanical parameters of matrix and impurities, substituting the mechanical parameters into the grid model to calculate related physical mechanical parameters of the coal blocks with different volumes, and thus obtaining a representation unit volume and corresponding parameters, wherein the method adopts the following technical scheme in order to achieve the purpose:
a coal-rock mass multi-scale analysis method based on industrial CT comprises the following steps:
s101: selecting a coal block body on a mine coal mining working face, wherein the shape of the block body can be any, but the minimum length of each edge of the block body is required to be more than 1.5 m;
s102, cutting the coal body block in the S101 into a cube of 1m × 1m × 1m by adopting a mine saw;
s103, cutting the cube in the S102 into 1000 small coal blocks of 0.1m × 0.1.1 m × 0.1.1 m, and numbering each coal block in sequence according to the position of each coal block before cutting;
s104: grinding the coal bodies cut in the step S102 into coal powder, and respectively finding out a matrix part and an inclusion part;
s105: respectively remolding the matrix and the inclusion in the coal dust, and then respectively carrying out a triaxial compression test to obtain mechanical parameters of the matrix and the inclusion in the coal briquette;
s106: loading and scanning the small coal blocks in the step S103 by using a loading type industrial CT (computed tomography), and acquiring two-dimensional gray images of the internal fracture expansion development state of the coal rock test piece under different loads; performing median filtering, threshold segmentation and image shearing on a two-dimensional gray image obtained in an experiment by using MATLAB software, performing three-dimensional reconstruction on the processed two-dimensional gray image by using median interpolation, data compression and volume rendering processes to obtain the distribution of matrixes, pores and inclusions in each coal briquette, and introducing the distribution into numerical simulation software to establish a coal sample grid model so as to obtain a grid model of 1000 small coal briquettes;
s107: obtaining cubic coal block grid models with different volume sizes according to the position and the number of each coal block before cutting in the step S103;
s108: assigning the matrix and inclusion in the cubic coal block grid models with different volume sizes in the step S107 according to the mechanical parameters in the step S105, substituting the assigned matrix and inclusion into numerical simulation software for calculation, and recording the related physical mechanical parameters of the coal blocks with different volumes;
s109: the physical parameters of the coal body are reduced along with the increase of the volume of the coal briquette, and the physical parameters are not changed when the volume of the coal body reaches the REV; therefore, finding out the point where the physical parameter does not change with the volume is the corresponding REV point, and the physical parameter corresponding to the point is the physical parameter of the coal body representation unit volume;
the cube cutting and numbering method in step S103 specifically includes the following steps:
step 1, drawing nine transverse thin lines and nine longitudinal thin lines at equal intervals on each surface of a 1m × 1m × 1m cube large coal block, namely dividing each surface into 100 identical small squares;
step 2, taking the right lower end of the cube coal briquette as an origin, dividing three edges intersected with the origin into an X axis, a Y axis and a Z axis respectively, sequencing the divided coal briquettes along the X axis, and sequentially sequencing 1 and 2 … 10 from the origin of the X axis to the X axis end point of the coal briquettes; sorting the divided coal blocks along the Y axis, and sorting 1,2 … 10 from the origin of the Y axis to the end point of the Y axis of the coal blocks; sequencing the divided coal blocks along the Z axis, and sequencing 1,2 … 10 from the origin of the Z axis to the end point of the Z axis of the coal blocks;
step 3, numbering 1000 small coal blocks according to the sequence, wherein the number of each small coal block is XiYjZk, i is the sequence of the coal blocks on the X axis, j is the sequence of the coal blocks on the Y axis, and k is the sequence of the coal blocks on the Z axis;
step 4, cutting off each small coal block along the drawn thin line, namely cutting off 1000 small coal blocks of 0.1m × 0.1.1 m × 0.1.1 m, wherein the corresponding number of each small coal block is XiYjZk;
the method for acquiring the matrix and inclusion parts in the pulverized coal in the step S104 specifically comprises the following steps:
step 1, taking a block 1dm3The remaining coal briquette is cut off in the step S102, and the mass m of the coal briquette is weighed by an electronic scale; putting into a cylindrical measuring cup capable of completely putting the coal briquette down, and adding more than 1dm3Reading the volume V1 corresponding to the water surface position at the beginning, slowly putting the coal briquette into the water, reading the volume V2 corresponding to the water surface position at the moment again after the water surface is calm, and obtaining the volume V3 of the coal briquette as (V2-V1); the density of the coal briquette is rho-m/V3;
step 2, crushing the residual coal blocks cut in the step 102 into coal blocks with the granularity of below 25mm by using a hammer crusher, and grinding the crushed coal blocks into coal powder with the granularity of below 90 mu m by using a high-pressure micro-grinder;
step 3, carrying out heavy liquid centrifugal separation on the coal powder obtained in the step 2; the specific gravity liquid is JY type nontoxic temperature-variable specific gravity liquid developed by Jilin metallurgy research institute, and the density rho of the coal briquette obtained in the step 1 is (rho-0.5) g/cm3～(ρ+0.5)g/cm3Ten groups of specific gravity liquid are arranged at equal intervals, and the capacity of each group is 1000 mL; adding 100cm into each group3Observing the separation amount of density substances at each level in each group of the uniformly mixed coal dust, and finding out a group with the maximum separation degree;
step 4, preparing 100L of specific gravity liquid with the same density as that of the group with the maximum separation degree in the step 3, and adding 0.01cm3After the coal powder is fully separated, collecting obtained density objects at all levels, wherein the density objects comprise a coal powder matrix and two inclusion parts, and respectively attaching labels to the two parts; namely, the acquisition of the matrix and the inclusion part in the coal dust is completed;
the method for respectively performing remodeling and mechanical parameter acquisition on the matrix and the inclusion in the pulverized coal in the step S105 comprises the following steps:
step 1, mixing 160cm3The coal powder substrate obtained in the step S105 was put into a cylindrical mold vessel having a diameter of × and a height of 50 × 100mm, and 20cm was further added320mL of the concrete is uniformly stirred to fill the whole container;
step 2, repeating the step 1 for 15 times to complete the remodeling of the matrix of the 15 cylindrical coal bodies;
step 3, standing for 20 days for drying, and opening a mold after 20 days to obtain a molded coal powder matrix cylindrical block;
step 4, carrying out confining pressure experiments under the pressure of 5MPa, 10MPa and 20MPa on the cylindrical blocks of the coal powder matrix in the step 3, carrying out 5 confining pressures on each cylindrical block to obtain the strength and the elastic modulus of 15 cylindrical blocks of the coal powder matrix, and constructing a Mokolun circle by using the strength values under the three confining pressures to obtain the cohesive force and the internal friction angle of the coal powder matrix;
step 5, taking the elastic modulus average value of the 15 coal powder matrix cylindrical blocks obtained in the step 4 as the elastic modulus of the coal powder matrix;
step 6, performing remodeling and triaxial compression on the pulverized coal inclusion part according to the steps 1,2, 3, 4 and 5 to obtain 15 pulverized coal inclusion cylindrical blocks of 0.1m × 0.1.1 m × 0.1.1 m, performing confining pressure experiments under the conditions of 5MPa, 10MPa and 20MPa, and obtaining the elastic modulus, cohesive force and internal friction angle of the pulverized coal inclusion;
the method for obtaining mesh models with different volume sizes in step S107 specifically includes:
step 1, small coal blocks of 0.1m × 0.1, 0.1m × 0.1.1 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 1, small coal blocks of 0.2m × 0.2, 0.2m × 0.2.2 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 2, small coal blocks of 0.3m × 0.3, 0.3m × 0.3.3 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 3, … … 1m × 1m × 1m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 10;
step 2, combining the grid models of the small coal blocks obtained in the step 106 according to the step 1 to obtain cubic coal block grid models with different volume sizes, wherein the cubic coal block grid models are coal blocks with the size of 0.1m × 0.1m × 0.1.1 m, coal blocks with the size of 0.2m × 0.2m × 0.2.2 m, coal blocks with the size of 0.3m × 0.3.3 m × 0.3.3 m … … to coal blocks with the size of 1m × 1m × 1 m;
the coal briquette assignment and numerical compression method in step S108 specifically includes the following steps:
step 1, assigning the elastic modulus, cohesive force and internal friction angle of the matrix obtained in the step S105 to the matrix part of the grid model in the step S106, and assigning the elastic modulus, cohesive force and internal friction angle of inclusions obtained in the step S105 to the inclusion part of the grid model in the step S106;
step 2, carrying out a numerical compression experiment by using FLAC3D, respectively carrying out numerical uniaxial compression on a coal block with the volume of 0.1m × 0.1m × 0.1m, a coal block with the volume of 0.2m × 0.2.2 m × 0.2m and a coal block with the volume of 0.3m × 0.3.3 m × 0.3m, wherein the coal block with the volume of … … 1m × 1m × 1m is … … m, the upper surface and the lower surface of the coal block are compression surfaces, the compression rate is 0.0001m/s, the left surface and the right surface and the front surface are free surfaces, and recording relevant physical parameters of the coal block at different volumes, including elastic modulus, compressive strength and residual strength;
step 3, respectively drawing a graph of the change of the elastic modulus, the compressive strength and the residual strength of the coal blocks along with the volume of the coal blocks by using the obtained data;
the method for finding out the physical parameters of the coal body characterization unit volume in the step S109 specifically comprises the following steps:
step 1, finding out a point of which the elastic modulus does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the elastic modulus corresponding to the point is the elastic modulus of the representation unit volume of the coal body;
step 2, finding out a point of which the compressive strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the compressive strength corresponding to the point is the compressive strength of the representation unit volume of the coal body;
and 3, finding out a point of which the residual strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the residual strength corresponding to the point is the residual strength of the representation unit volume of the coal body.
The specific embodiment described in the invention is merely an illustration of a coal-rock mass multi-scale mechanical property analysis method based on industrial CT. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Compared with the prior art, the invention has the following advantages:
the traditional acquisition of the internal structure composition is mainly based on statistics, the obtained internal structure only has statistical significance, the internal real situation is often difficult to verify, and the obtained result is difficult to judge whether the internal structure composition is correct or not. The method can reproduce the real structure in the coal body, so that the physical properties of the coal body can be accurately analyzed and judged.
The invention aims at the problems in the prior art, one purpose of the invention is to provide a novel coal-rock mass multi-scale analysis idea based on industrial CT, and the invention overcomes the defect that the multi-scale characteristics of coal-rock mass cannot be truly reflected by a statistical method in the conventional multi-scale analysis method, and the other purpose of the invention is to construct an analysis method of coal-rock mass multi-scale mechanical characteristics matched with CT scanning.
Detailed Description
A coal-rock mass multi-scale analysis method based on industrial CT comprises the following steps:
s101: the coal body block can be selected on the working face of coal mining of the mine, and the shape of the block can be any, but the minimum length of each edge of the block is required to be more than 1.5 m.
And S102, cutting the coal block in the S101 into cubes of 1m × 1m × 1m by using a mine saw (model: KSG-3600).
And S103, cutting the cube in the S102 into 1000 small coal blocks of 0.1m × 0.1.1 m × 0.1.1 m, and numbering each coal block in sequence according to the position of each coal block before cutting.
S104: and (4) grinding the coal bodies remained after cutting in the step (S102) into coal powder, and respectively finding out a matrix part and an inclusion part.
S105: and respectively remolding the matrix and the inclusion in the coal dust, and then respectively carrying out a triaxial compression test to obtain the mechanical parameters of the matrix and the inclusion in the coal briquette.
S106: and (2) scanning and grid reconstruction are sequentially carried out on the small coal blocks in the step S103 by utilizing a loading type industrial CT (model: ACTIS300-320/225) according to the method of 'a loaded coal rock damage constitutive equation construction method based on CT scanning' to obtain the distribution of matrixes, pores and inclusions in each coal block, and a numerical simulation software is introduced to establish a coal sample grid model, so that the grid model of 1000 small coal blocks can be obtained.
S107: and obtaining cubic coal block grid models with different volume sizes according to the position and the number of each coal block before cutting in the step S103.
S108: and assigning the matrix and inclusion in the cubic coal block grid models with different volume sizes in the step S107 according to the mechanical parameters in the step S105, substituting the assigned matrix and inclusion into numerical simulation software for calculation, and recording the related physical mechanical parameters of the coal blocks with different volumes.
S109: the physical parameters of the coal body are reduced along with the increase of the volume of the coal briquette, and the physical parameters are not changed when the volume of the coal briquette reaches the REV. Therefore, the point at which the physical parameter does not change with the volume is found to be the corresponding REV point, and the physical parameter corresponding to the point is the physical parameter of the coal body characterization unit volume.
The cube cutting and numbering method in step S103 specifically includes the following steps:
step 1, drawing nine transverse thin lines and nine longitudinal thin lines at equal intervals on each surface of a 1m × 1m × 1m cube large coal block, namely dividing each surface into 100 identical small squares.
And 2, taking the right lower end of the cube coal briquette as an origin, dividing three edges intersected with the origin into an X axis, a Y axis and a Z axis respectively, sequencing the divided coal briquettes along the X axis, and sequentially sequencing 1 and 2 … 10 from the origin of the X axis to the X axis of the coal briquette.
The divided coal blocks are sorted again along the Y-axis and sorted from the Y-axis origin to the Y-axis end of the coal block by 1,2 … 10. The divided coal blocks are sorted along the Z axis, and the coal blocks are sorted from the Z-axis origin to the Z-axis end of the coal blocks by 1,2 … 10.
Step 3, numbering 1000 small coal blocks according to the sequence, wherein the numbering is X respectivelyiYjZkWherein i is the sequence of the coal blocks corresponding to the X axis, j is the sequence of the coal blocks corresponding to the Y axis, and k is the sequence of the coal blocks corresponding to the Z axis.
Step 4, cutting off each small coal block along the drawn thin line, namely 1000 small coal blocks with the number of X and the corresponding number of 0.1m × 0.1.1 m × 0.1.1 miYjZk。
The method for acquiring the matrix and inclusion parts in the pulverized coal in the step S104 specifically comprises the following steps:
step 1, taking a block 1dm3Left and right (approximate, not precise) steps S102 cut the remaining coal briquette, and weigh its mass m with an electronic scale. Putting into a cylindrical measuring cup capable of completely putting the coal briquette down, and adding more than 1dm3Reading the volume V corresponding to the water surface position at the initial time1Slowly putting coal blocks into the water surface, and reading out the volume V corresponding to the water surface position again after the water surface is calm2The volume V of the coal block can be obtained3Is (V)2-V1). The density of the coal block is rho-m/V3。
And 2, crushing the residual coal blocks cut in the step 102 into coal blocks with the granularity of less than 25mm by using a hammer crusher (model: PC phi 400 × 300), and grinding the crushed coal blocks into coal powder with the granularity of less than 90 mu m by using a high-pressure type micro-powder mill (model: YGM 9531).
And 3, carrying out heavy liquid centrifugal separation on the coal powder obtained in the step 2. The specific gravity liquid is JY type nontoxic temperature-variable specific gravity liquid developed by Jilin metallurgy research institute, and the density rho of the coal briquette obtained in the step 1 is (rho-0.5) g/cm3～(ρ+0.5)g/cm3Ten groups of specific gravity liquid are arranged at equal intervals, and the capacity of each group is 1000 mL. Adding 100cm into each group3And observing the separation amount of density substances of each level in each group of the uniformly mixed coal powder, and finding out a group with the maximum separation degree.
Step 4, preparing 100L of specific gravity liquid with the same density as that of the group with the maximum separation degree in the step 3, and adding 0.01cm3After the coal powder is fully separated, the obtained density objects at all levels are collected, and the density objects comprise a coal powder substrate and two inclusion parts (wherein the coal powder substrate part floats on the upper part of the specific gravity liquid, and the inclusion part sinks on the bottom part), and labels are respectively stuck on the coal powder substrate and the inclusion parts. Namely, the obtaining of the matrix and the inclusion part in the coal powder is completedAnd (6) taking.
The method for respectively performing remodeling and mechanical parameter acquisition on the matrix and the inclusion in the pulverized coal in the step S105 comprises the following steps:
step 1, mixing 160cm3The coal powder substrate obtained in the step S105 was put into a cylindrical mold vessel having a diameter of × and a height of 50 × 100mm, and 20cm was further added320mL of concrete, and stirred well to fill the entire container.
And 2, repeating the step 1 for 15 times to complete the remodeling of the matrix of the 15 cylindrical coal bodies.
And 3, standing for 20 days for drying, and opening the mold after 20 days to obtain the molded coal powder matrix cylindrical block.
And 4, carrying out confining pressure experiments under the conditions of 5MPa, 10MPa and 20MPa on the cylindrical blocks of the coal powder matrix in the step 3, carrying out 5 confining pressures on each cylindrical block to obtain the strength and the elastic modulus of 15 cylindrical blocks of the coal powder matrix, and constructing a Mokolun circle by using the strength values under the three confining pressures to obtain the cohesive force and the internal friction angle of the coal powder matrix.
And 5, taking the elastic modulus average value of the 15 cylindrical blocks of the coal powder matrix obtained in the step 4 as the elastic modulus of the coal powder matrix.
And 6, performing remodeling and triaxial compression on the pulverized coal inclusion part according to the steps 1,2, 3, 4 and 5 to obtain 15 pulverized coal inclusion cylindrical blocks of 0.1m × 0.1.1 m × 0.1.1 m, performing confining pressure experiments under the conditions of 5MPa, 10MPa and 20MPa, and obtaining the elastic modulus, cohesive force and internal friction angle of the pulverized coal inclusion.
The method for obtaining mesh models with different volume sizes in step S107 specifically includes:
the small coal blocks of 0.1m × 0.1, 0.1m × 0.1.1 m in step 1 refer to the combination of all the coal blocks with the coal block numbers i, j and k being less than or equal to 1, the small coal blocks of 0.2m × 0.2, 0.2m × 0.2.2 m refer to the combination of all the coal blocks with the coal block numbers i, j and k being less than or equal to 2, and the small coal blocks of 0.3m × 0.3, 0.3m × 0.3.3 m refer to the combination of all the coal blocks with the coal block numbers i, j and k being less than or equal to 3, and the coal block volume of … … 1m × 1m × 1m refers to the combination of all the coal blocks with the coal block numbers i, j and k being less than or equal to 10.
And 2, combining the grid models of the small coal blocks obtained in the step 106 according to the step 1 to obtain cubic coal block grid models with different volume sizes, wherein the cubic coal block grid models are coal blocks with the volume sizes ranging from 0.1m × 0.1m × 0.1.1 m, 0.2m × 0.2m × 0.2.2 m, 0.3m × 0.3.3 m × 0.3.3 m … … to 1m × 1m × 1 m.
The coal briquette assignment and numerical compression method in step S108 specifically includes the following steps:
step 1, assigning the matrix elastic modulus, the cohesive force and the internal friction angle obtained in the step S105 to a matrix part of the grid model in the step S106, and assigning the inclusion elastic modulus, the cohesive force and the internal friction angle obtained in the step S105 to an inclusion part of the grid model in the step S106.
Step 2, utilizing FLAC3DA numerical compression experiment is carried out, numerical uniaxial compression is respectively carried out on a coal block with the volume of 0.1m × 0.1m × 0.1.1 m, a coal block with the volume of 0.2m × 0.2m × 0.2.2 m and a coal block with the volume of 0.3m × 0.3.3 m × 0.3.3 m, namely a coal block with the volume of … … 1m × 1m × 1m, the upper surface and the lower surface of the coal block are compression surfaces, the compression rate is 0.0001m/s, the left surface, the right surface, the front surface, the rear surface and the left surface are free surfaces, and relevant physical parameters of the coal block at different volumes are recorded, wherein the relevant physical parameters comprise elastic modulus, compressive strength and residual strength.
And 3, respectively drawing a graph of the change of the elastic modulus, the compressive strength and the residual strength of the coal blocks along with the volume of the coal blocks by using the obtained data.
The method for finding out the physical parameters of the coal body characterization unit volume in the step S109 specifically comprises the following steps:
step 1, finding out a point in the graph where the elastic modulus no longer changes with the volume, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the elastic modulus corresponding to the point is the elastic modulus of the representation unit volume of the coal body.
And 2, finding out a point of which the compressive strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the compressive strength corresponding to the point is the compressive strength of the representation unit volume of the coal body.
And 3, finding out a point of which the residual strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the residual strength corresponding to the point is the residual strength of the representation unit volume of the coal body.
The specific embodiment described in the invention is merely an illustration of a coal-rock mass multi-scale mechanical property analysis method based on industrial CT. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (1)
1. A coal-rock mass multi-scale analysis method based on industrial CT comprises the following steps:
s101: selecting a coal block body on a mine coal mining working face, wherein the shape of the block body can be any, but the minimum length of each edge of the block body is required to be more than 1.5 m;
s102, cutting the coal body block in the S101 into a cube of 1m × 1m × 1m by adopting a mine saw;
s103, cutting the cube in the S102 into 1000 small coal blocks of 0.1m × 0.1.1 m × 0.1.1 m, and numbering each coal block in sequence according to the position of each coal block before cutting;
s104: grinding the coal bodies cut in the step S102 into coal powder, and respectively finding out a matrix part and an inclusion part;
s105: respectively remolding the matrix and the inclusion in the coal dust, and then respectively carrying out a triaxial compression test to obtain mechanical parameters of the matrix and the inclusion in the coal briquette;
s106: loading and scanning the small coal blocks in the step S103 by using a loading type industrial CT (computed tomography), and acquiring two-dimensional gray images of the internal fracture expansion development state of the coal rock test piece under different loads; performing median filtering, threshold segmentation and image shearing on a two-dimensional gray image obtained in an experiment by using MATLAB software, performing three-dimensional reconstruction on the processed two-dimensional gray image by using median interpolation, data compression and volume rendering processes to obtain the distribution of matrixes, pores and inclusions in each coal briquette, and introducing the distribution into numerical simulation software to establish a coal sample grid model so as to obtain a grid model of 1000 small coal briquettes;
s107: obtaining cubic coal block grid models with different volume sizes according to the position and the number of each coal block before cutting in the step S103;
s108: assigning the matrix and inclusion in the cubic coal block grid models with different volume sizes in the step S107 according to the mechanical parameters in the step S105, substituting the assigned matrix and inclusion into numerical simulation software for calculation, and recording the related physical mechanical parameters of the coal blocks with different volumes;
s109: the physical parameters of the coal body are reduced along with the increase of the volume of the coal briquette, and the physical parameters are not changed when the volume of the coal body reaches the REV; therefore, finding out the point where the physical parameter does not change with the volume is the corresponding REV point, and the physical parameter corresponding to the point is the physical parameter of the coal body representation unit volume;
the cube cutting and numbering method in step S103 specifically includes the following steps:
step 1, drawing nine transverse thin lines and nine longitudinal thin lines at equal intervals on each surface of a 1m × 1m × 1m cube large coal block, namely dividing each surface into 100 identical small squares;
step 2, taking the right lower end of the cube coal briquette as an origin, dividing three edges intersected with the origin into an X axis, a Y axis and a Z axis respectively, sequencing the divided coal briquettes along the X axis, and sequentially sequencing 1 and 2 … 10 from the origin of the X axis to the X axis end point of the coal briquettes; sorting the divided coal blocks along the Y axis, and sorting 1,2 … 10 from the origin of the Y axis to the end point of the Y axis of the coal blocks; sequencing the divided coal blocks along the Z axis, and sequencing 1,2 … 10 from the origin of the Z axis to the end point of the Z axis of the coal blocks;
step 3, numbering 1000 small coal blocks according to the sequence, wherein the number of each small coal block is XiYjZk, i is the sequence of the coal blocks on the X axis, j is the sequence of the coal blocks on the Y axis, and k is the sequence of the coal blocks on the Z axis;
step 4, cutting off each small coal block along the drawn thin line, namely cutting off 1000 small coal blocks of 0.1m × 0.1.1 m × 0.1.1 m, wherein the corresponding number of each small coal block is XiYjZk;
the method for acquiring the matrix and inclusion parts in the pulverized coal in the step S104 specifically comprises the following steps:
step 1, taking a block 1dm3The remaining coal briquette is cut off in the step S102, and the mass m of the coal briquette is weighed by an electronic scale; putting into a cylindrical measuring cup capable of completely putting the coal briquette down, and adding more than 1dm3Reading the volume V1 corresponding to the water surface position at the beginning, slowly putting the coal briquette into the water, reading the volume V2 corresponding to the water surface position at the moment again after the water surface is calm, and obtaining the volume V3 of the coal briquette as (V2-V1); the density of the coal briquette is rho-m/V3;
step 2, crushing the residual coal blocks cut in the step 102 into coal blocks with the granularity of below 25mm by using a hammer crusher, and grinding the crushed coal blocks into coal powder with the granularity of below 90 mu m by using a high-pressure micro-grinder;
step 3, carrying out heavy liquid centrifugal separation on the coal powder obtained in the step 2; the specific gravity liquid is JY type nontoxic temperature-variable specific gravity liquid developed by Jilin metallurgy research institute, and the density rho of the coal briquette obtained in the step 1 is (rho-0.5) g/cm3～(ρ+0.5)g/cm3Ten groups of specific gravity liquid are arranged at equal intervals, and the capacity of each group is 1000 mL; adding 100cm into each group3Observing the separation amount of density substances at each level in each group of the uniformly mixed coal dust, and finding out a group with the maximum separation degree;
step 4, preparing 100L of specific gravity liquid with the same density as that of the group with the maximum separation degree in the step 3, and adding 0.01cm3After the coal powder is fully separated, collecting obtained density objects at all levels, wherein the density objects comprise a coal powder matrix and two inclusion parts, and respectively attaching labels to the two parts; namely, the acquisition of the matrix and the inclusion part in the coal dust is completed;
the method for respectively performing remodeling and mechanical parameter acquisition on the matrix and the inclusion in the pulverized coal in the step S105 comprises the following steps:
step 1, mixing 160cm3The coal powder substrate obtained in the step S105 was put into a cylindrical mold vessel having a diameter of × and a height of 50 × 100mm, and 20cm was further added320mL of the concrete is uniformly stirred to fill the whole container;
step 2, repeating the step 1 for 15 times to complete the remodeling of the matrix of the 15 cylindrical coal bodies;
step 3, standing for 20 days for drying, and opening a mold after 20 days to obtain a molded coal powder matrix cylindrical block;
step 4, carrying out confining pressure experiments under the pressure of 5MPa, 10MPa and 20MPa on the cylindrical blocks of the coal powder matrix in the step 3, carrying out 5 confining pressures on each cylindrical block to obtain the strength and the elastic modulus of 15 cylindrical blocks of the coal powder matrix, and constructing a Mokolun circle by using the strength values under the three confining pressures to obtain the cohesive force and the internal friction angle of the coal powder matrix;
step 5, taking the elastic modulus average value of the 15 coal powder matrix cylindrical blocks obtained in the step 4 as the elastic modulus of the coal powder matrix;
step 6, performing remodeling and triaxial compression on the pulverized coal inclusion part according to the steps 1,2, 3, 4 and 5 to obtain 15 pulverized coal inclusion cylindrical blocks of 0.1m × 0.1.1 m × 0.1.1 m, performing confining pressure experiments under the conditions of 5MPa, 10MPa and 20MPa, and obtaining the elastic modulus, cohesive force and internal friction angle of the pulverized coal inclusion;
the method for obtaining mesh models with different volume sizes in step S107 specifically includes:
step 1, small coal blocks of 0.1m × 0.1, 0.1m × 0.1.1 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 1, small coal blocks of 0.2m × 0.2, 0.2m × 0.2.2 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 2, small coal blocks of 0.3m × 0.3, 0.3m × 0.3.3 m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 3, … … 1m × 1m × 1m refer to the combination of all the coal blocks with coal block numbers i, j and k being less than or equal to 10;
step 2, combining the grid models of the small coal blocks obtained in the step 106 according to the step 1 to obtain cubic coal block grid models with different volume sizes, wherein the cubic coal block grid models are coal blocks with the size of 0.1m × 0.1m × 0.1.1 m, coal blocks with the size of 0.2m × 0.2m × 0.2.2 m, coal blocks with the size of 0.3m × 0.3.3 m × 0.3.3 m … … to coal blocks with the size of 1m × 1m × 1 m;
the coal briquette assignment and numerical compression method in step S108 specifically includes the following steps:
step 1, assigning the elastic modulus, cohesive force and internal friction angle of the matrix obtained in the step S105 to the matrix part of the grid model in the step S106, and assigning the elastic modulus, cohesive force and internal friction angle of inclusions obtained in the step S105 to the inclusion part of the grid model in the step S106;
step 2, carrying out a numerical compression experiment by using FLAC3D, respectively carrying out numerical uniaxial compression on a coal block with the volume of 0.1m × 0.1m × 0.1m, a coal block with the volume of 0.2m × 0.2.2 m × 0.2m and a coal block with the volume of 0.3m × 0.3.3 m × 0.3m, wherein the coal block with the volume of … … 1m × 1m × 1m is … … m, the upper surface and the lower surface of the coal block are compression surfaces, the compression rate is 0.0001m/s, the left surface and the right surface and the front surface are free surfaces, and recording relevant physical parameters of the coal block at different volumes, including elastic modulus, compressive strength and residual strength;
step 3, respectively drawing a graph of the change of the elastic modulus, the compressive strength and the residual strength of the coal blocks along with the volume of the coal blocks by using the obtained data;
the method for finding out the physical parameters of the coal body characterization unit volume in the step S109 specifically comprises the following steps:
step 1, finding out a point of which the elastic modulus does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the elastic modulus corresponding to the point is the elastic modulus of the representation unit volume of the coal body;
step 2, finding out a point of which the compressive strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the compressive strength corresponding to the point is the compressive strength of the representation unit volume of the coal body;
and 3, finding out a point of which the residual strength does not change along with the volume in the graph, wherein the volume corresponding to the point is the representation unit volume of the coal body, and the residual strength corresponding to the point is the residual strength of the representation unit volume of the coal body.
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