A method for calibrating broken coal rock mass compaction reconstruction

Abstract

The application provides a broken coal rock mass compaction rebuilding calibration method, first obtains the ground stress parameters of the position of the second mining working face based on the geological conditions of the research area; the regenerative coal body is obtained by designing the compaction rebuilding with a hierarchical loading mode, the ground stress test results are used to determine the hierarchical loading mode of each level load stress and time; the coal rock particle size grading used in the test of the size of the broken coal rock mass is investigated, the compaction regenerative coal body rebuilding test is carried out according to the designed hierarchical loading mode, the regenerative coal body rebuilding sample is obtained; the related physical and mechanical parameters of the regenerative coal body rebuilding sample are obtained by testing, and finally the relationship between the fractal dimension of the broken coal rock mass in the goaf and the compaction time is obtained by combining the fractal dimension change model considering the time effect. The specific rebuilding process of the compaction regenerative coal body of the coal mine second mining working face is given, the fractal dimension change model considering the time effect is established, and reference is provided for the safe and efficient mining of the coal mine second mining working face.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal mining, and particularly relates to a broken coal rock mass compaction re-establishment calibration method. BACKGROUND

[0002] With long-term large-scale exploitation of coal resources, in order to ensure the sustainable supply of coal resources, the re-mining of early un-mined residual coal resources has gradually been valued, and more and more coal mines have entered the stage of re-mining of residual coal resources. The re-mining of residual coal resources has become an important development direction to ensure the national energy supply and the sustainable development of the coal industry. The residual coal in the re-mining working face is mixed with the caved rock mass and gradually forms a regenerated coal body after long-term compaction. This regenerated coal body is the main object of the re-mining of residual coal. Related scholars have conducted a large number of studies on the re-mining of residual coal. Based on different re-mining conditions, various types of re-mining methods such as water mining, comprehensive mechanized long-arm re-mining and filling re-mining have been proposed. However, there is no specific laboratory-scale re-mining working face regenerated coal body re-establishment method at present, and the study of the mechanical strength and permeability characteristics of the residual coal in the re-mining working face is still the key and difficulty of the safety production of the re-mining working face. SUMMARY

[0003] The purpose of the present application is to provide a broken coal rock mass compaction re-establishment calibration method. The device provides a re-mining working face regenerated coal body compaction re-establishment process and constructs a fractal dimension change model considering the time effect, which is of great significance for studying the properties of the re-mining working face compaction regenerated coal body and estimating the compaction period.

[0004] In order to achieve the above-mentioned purpose of the application, the present application obtains the ground stress at the location of the re-mining working face by studying the geological data and ground stress test of the research area, designs the compaction time and compaction force based on the stress state change law of the caved coal rock mass in the goaf of the engineering site, adopts a graded loading method to compact and re-establish the regenerated coal body, tests the related physical and mechanical parameters of the regenerated coal body re-establishment sample, and constructs a relationship between the fractal dimension of the caved coal rock mass in the goaf and the compaction time, which is specifically as follows:

[0005] The present application provides a broken coal rock mass compaction re-establishment calibration method, which comprises the following steps:

[0006] (1) Based on the geological conditions of the research area, the ground stress parameters of the re-mining working face area are obtained by stress relief method or stress recovery method;

[0007] (2) According to the mine pressure principle and the rock mass movement law, the regenerated coal body is obtained by adopting a graded loading method, and the load parameters of each level in the graded loading method are determined by the following formula combined with the ground stress test results:

[0008]

[0009] In the formula, σi σ represents the load values ​​for each level, in MPa; i represents the number of loading levels; σ n σ is the measured ground stress value, MPa, where n is the maximum graded loading level; j For less than σ n / 2 is the maximum graded load value, where j is the corresponding graded loading level; σ j+1 σ is the load value for level j+1; n+1 This represents the load value for level n+1; σ m The maximum applied graded load value; the function f(x) = [x] is a Gaussian function, where [x] represents the integer part of the real number x, that is, [x] represents the largest integer not exceeding the real number x; k is a constant, ranging from 0.1 to 0.2 MPa.

[0010] In the graded loading method, after each level of load has stabilized, the next level of loading is applied. The next level of load is applied when the vertical deformation of the specimen at each level of the graded load is less than 0.0075 mm per hour.

[0011] (3) Investigate the size of the crushed coal and rock mass on site, and determine the particle size distribution of the coal and rock mass to be used in the laboratory based on the similarity ratio principle; carry out compaction and reconstruction tests of recycled coal according to the designed graded loading method, and finally obtain recycled coal reconstruction samples under the corresponding geological conditions. Test the relevant physical and mechanical parameters of the recycled coal reconstruction samples, including the elastic modulus, viscoelastic modulus, viscosity coefficient and porosity of the crushed coal and rock mass.

[0012] (4) By combining the creep model of the western body and the fractal model of the porosity of the broken coal and rock mass, a fractal dimension change model considering the time effect is established. The relevant physical and mechanical parameters of the recycled coal reconstructed sample are substituted into the model to finally obtain the relationship between the fractal dimension of the broken coal and rock mass in the goaf and the compaction time.

[0013] Based on the principles of mine pressure and the laws of rock mass movement, the broken coal and rock mass in the goaf will successively experience the natural accumulation state, stress recovery state and recompaction state in the direction of working face advancement, and the stress gradually increases to the ground stress. According to this design, a graded loading method is adopted to rebuild the recycled coal body and reproduce the stress state of the broken coal and rock mass in the goaf.

[0014] Preferably, in step S4, the fractal dimension change model considering time effects is:

[0015]

[0016] In the formula, The porosity function of the fractured coal and rock mass is given by time t and obtained through porosity test fitting under different time conditions; σ is the in-situ stress, MPa; E1 and E2 are the elastic modulus and viscoelastic modulus of the fractured coal and rock mass, respectively; η is the viscosity coefficient of the fractured coal and rock mass; t is the compaction time; e is the Euler number, which is approximately 2.71828 and is an exponential function. The base value; ρ0 is the apparent density of the fractured coal and rock mass, kg / m³ 3 ;ρ s The true density of the fractured coal and rock mass is kg / m³. 3 ;d max Maximum particle size, mm; d min denoted as minimum particle size (mm); D represents the fractal dimension of the fractured coal and rock mass. Through field investigation and testing, the fractal dimension parameters of the compacted fractured coal and rock mass underground were obtained. Combined with the fractal dimension variation model, the relationship between the compaction time and the fractal dimension of the fractured coal and rock mass in the underground goaf was obtained.

[0017] Preferably, in step S4, the formula for calculating the fractal dimension is:

[0018] ln[m1(d i ) / m t ]=(3-D)ln(d i / d max )

[0019] In the formula, m1(d i ) represents particles with a diameter less than d i Partial rock particle mass, kg; m t Total mass, kg; d i The size characteristic scale for a certain particle is in mm.

[0020] Preferably, in step S3, the mechanical and permeability characteristics of the compacted recycled coal body in the re-mining face are obtained through mechanical and permeability tests.

[0021] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a complete process for compacting and reconstructing recycled coal in a re-mining face. It can reproduce recycled coal samples from the reconstructed mining face on a laboratory scale. Through experimental analysis of the recycled coal's properties, its main property parameters can be determined. Combining the physical and mechanical parameters of the recycled coal with a fractal dimension variation model considering the time effect, the relationship between the fractal dimension of the broken coal and rock mass in the goaf and the compaction time is finally obtained. This method is simple to operate and yields reliable results, providing a reliable theoretical basis for the recovery of residual coal and disaster prevention in re-mining faces, further promoting the development of residual coal recovery technology, and has wide applicability. Attached Figure Description

[0022] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification, illustrate embodiments of the application, and together with the description serve to explain the application, and do not limit the application.

[0023] Figure 1 A flow chart of a broken coal and rock mass compaction and re-construction calibration method is provided in an embodiment of the application. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. Of course, the specific embodiments described herein are only used to explain the application, and do not limit the application.

[0025] Reference is made to Figure 1 The embodiment provides a broken coal and rock mass compaction and re-construction calibration method, and specifically comprises the following steps.

[0026] First, the in-situ stress parameters of the position of the second mining working face are obtained based on the geological conditions of the research area; the regenerated coal body is obtained by designing a hierarchical loading method for compaction and re-construction, and the hierarchical load stress and time in the hierarchical loading method are determined according to the in-situ stress test results; the coal and rock mass particle size gradation used in the test is investigated, the compaction and re-construction test of the regenerated coal body is carried out according to the designed hierarchical loading method, and the regenerated coal body re-construction sample is obtained; the related physical and mechanical parameters of the regenerated coal body re-construction sample are tested, and finally the fractal dimension and compaction time relationship of the broken coal and rock mass in the goaf is obtained by combining the fractal dimension change model considering the time effect.

[0027] Next, the specific steps are as follows with the second mining working face of a certain mine as an example.

[0028] (1) Based on the geological conditions of the research area, the in-situ stress value of the second mining working face region is obtained by the drill hole casing stress relief method as 15 MPa.

[0029] (2) According to the mine pressure principle and the rock mass movement law, the hierarchical loading method is used to obtain the regenerated coal body by compaction and re-construction, and the hierarchical load parameters in the hierarchical loading method are determined by the following formula in combination with the in-situ stress test results:

[0030]

[0031] The hierarchical load parameters are obtained according to the above formula, as shown in Table 1:

[0032] Table 1 Compaction force hierarchical load value

[0033]

[0034] It is determined that when the deformation of each level sample of the hierarchical load is less than 0.0075 mm per hour vertical deformation, the next level load is applied.

[0035] (3) Investigate the size of the broken coal and rock mass, select the similar ratio of this test as 1:60, determine the particle size grading of the coal and rock mass less than 20mm in the laboratory as the test sample; carry out the compaction and regeneration of the coal body according to the design of the graded loading mode, finally obtain the regenerated coal body sample under the corresponding geological conditions, test the triaxial compressive strength of the regenerated coal body sample as 8.65MPa, and the permeability as 1.46x10 -11 m 2 , the void ratio The elastic modulus of the broken coal and rock mass E1 is 1226.28MPa, the viscoelastic modulus of the broken coal and rock mass E2 is 2965.8MPa, and the viscosity coefficient of the broken coal and rock mass η is 8.33.

[0036] (4) Substitute the related parameters of the regenerated coal body sample into the fractal dimension change model considering the time effect, obtain the relationship formula of the fractal dimension of the broken coal and rock mass in the goaf and the compaction time as:

[0037]

[0038] The present application obtains the ground stress at the position of the second mining face by studying the geological data and ground stress test of the region, designs the compaction time and compaction force based on the stress state change law of the collapsed coal and rock mass in the goaf of the engineering site, compacts and rebuilds the regenerated coal body by adopting the graded loading mode, tests the related physical and mechanical parameters of the regenerated coal body sample, and constructs the relationship formula of the fractal dimension of the broken coal and rock mass in the goaf and the compaction time.

[0039] The above only describes the preferred embodiments of the present application, and does not limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for calibrating the compaction of a coal rock mass broken by crushing, characterized by, The method comprises the following steps: S1, based on the geological conditions of the research area, the in-situ stress parameters of the area of the second mining face are obtained by stress relief method or stress recovery method test; S2, according to the mine pressure principle and the rock mass movement law, the regenerated coal body is obtained by compaction and reconstruction in a staged loading mode, the stress values of each level of load and the loading time are determined in combination with the in-situ stress test results, and the parameters of each level of load in the staged loading mode are determined by the following formula: ； wherein σ i is a load value at each stage, MPa; i is a stage number of the graded loading; σ n is a ground stress test value, MPa, wherein n is a maximum stage number of the graded loading; σ j is a maximum graded load value less than σ n / 2, j is a corresponding stage number of the graded loading; σ j+1 is a load value at the j+1 stage; σ n-1 is a load value at the n-1 stage, 0 MPa < σ n - σ n-1 ≤ 2.7 MPa; σ m is a maximum graded load value applied; [x] represents an integer part of a real number x, that is, [x] represents a maximum integer not exceeding the real number x; k is a constant, and is taken as 0.1-0.2 MPa; After the action of each level of load in the staged loading mode is stable, the next level of load is loaded, and when the deformation of each level of sample of the staged load is less than 0.0075mm per hour, the next level of load is applied; S3, the size of the broken coal and rock mass is investigated on site, the particle size gradation of the coal and rock mass used in the laboratory is determined based on the similarity ratio principle, the compaction and reconstruction test of the regenerated coal body is carried out according to the designed staged loading mode, and finally the regenerated coal body reconstruction sample under the corresponding geological conditions is obtained, and the related physical and mechanical parameters of the regenerated coal body reconstruction sample are tested, including the elastic modulus, viscoelastic modulus, viscous coefficient and void ratio of the broken coal and rock mass; S4, a fractal dimension change model considering time effect is established in combination with the Nishihara body creep model and the broken coal and rock mass void ratio fractal model, the related physical and mechanical parameters of the regenerated coal body reconstruction sample are substituted, and finally the relationship formula between the fractal dimension of the broken coal and rock mass in the goaf and the compaction time is obtained.

2. The method of claim 1, wherein, In step S4, the fractal dimension change model considering time effect is: ； In the formula, φ(t) is a function of the broken coal rock mass void ratio related to time t, which is obtained by fitting the void ratio test under different time conditions; σ is the ground stress, MPa; E1 and E2 are the elastic modulus and viscoelastic modulus of the broken coal rock mass, respectively; η is the viscosity coefficient of the broken coal rock mass; t is the compaction time; e is Euler's number, which is about 2.71828, and is the base of the exponential function; ρ0 is the apparent density of the broken coal rock mass, kg / m . 3 ​ ρ s For broken coal density, kg / m 3 ; d max D is the maximum particle size, mm; d min D is the minimum particle size, mm; D is the fractal dimension of the crushed coal rock mass; Through field investigation, the fractal dimension parameters of the underground compacted crushed coal rock mass are obtained, and the relationship between the compaction time of the crushed coal rock mass in the underground goaf and the fractal dimension is obtained by combining the fractal dimension change model.

3. The method of claim 2, wherein, In step S4, the calculation formula of the fractal dimension is: ； where m1(d i ) is the mass of rock particles having a size less than d i t is the total mass, kg; d i is a size characteristic dimension, mm.​ 4. The method of claim 1, wherein, In step S3, the mechanical and permeability test is used to test the mechanical and permeability characteristic parameters of the compaction regenerated coal body of the second mining face.

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