Construction method and calculation method of stope face steady-state direct current electric method detection model

Abstract

A stope face steady state direct current electric method detection model construction method and a calculation method adopt COMSOL numerical calculation software to realize mine stope face roof overlying strata deformation simulation, form a deformed overlying strata geometric deformation characteristic curve, establish a direct current electric method detection numerical calculation model under the constraint of the geometric deformation characteristic curve, and calculate the stope face steady state direct current electric method detection model. A mine direct current method and coal mining disturbance are closely combined, and the reliability of a numerical calculation result is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of geophysical exploration, and in particular relates to a method for constructing a steady-state direct current electrical detection model for a mining face and a calculation method. Background Art

[0002] With the continuous development of coal mining technology, the disturbance intensity of the roof overburden after coal seam mining in underground mines has increased, and coal mining is accompanied by serious threats of roof accidents. The direct current method is an important method for detecting geological information of the roof of the mining face, and the numerical calculation method is an important tool for the theoretical research of the direct current method technology. Therefore, according to the working environment of the roof of the mining face in the mine, the development of efficient and reliable numerical calculation methods for direct current detection is an important research direction for studying the application mechanism of direct current detection in the roof of the mining face in the mine.

[0003] In recent years, computer numerical calculation technology has been continuously developed, forming a variety of DC numerical calculation technologies such as finite difference, finite volume, and finite element. In fact, after coal resources are mined, the overlying rock layer of the coal seam will inevitably move due to the force. However, when simulating the detection of the roof of the mining face, the existing DC numerical calculation technology does not consider the influence of the mechanical parameters of the overlying surrounding rock on the displacement of the rock layer. The existing numerical simulation method of DC detection of the roof of the mining face is not closely integrated with the actual mining of the mine. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for constructing a steady-state DC electrical detection model and a calculation method for a mining face, so as to solve the problem of inaccurate data calculation results caused by the lack of close integration of existing methods with actual mine mining.

[0005] To achieve the above object, the technical solution adopted by the present invention includes:

[0006] A method for constructing a steady-state direct current electrical detection model for a mining face comprises the following steps:

[0007] S1, obtain the bulk modulus, shear modulus, cohesion, internal friction angle, density, resistivity and thickness of the overburden rock of the mining face before mining, and construct the roof overburden deformation model through the solid mechanics module of COMSOL;

[0008] S2, setting boundary conditions and peripheral conditions in the solid mechanics module of COMSOL, meshing the roof overburden deformation model obtained in S1, and then using the solver to calculate the deformation of the mining face under the influence of gravity before mining to obtain a deformation mesh model;

[0009] S3, setting the goaf area at the lower part of the deformed grid model obtained in S2 to obtain the post-mining stratum displacement model;

[0010] S4, setting the soil plasticity constraint condition and Mohr-Coulomb criterion in the solid mechanics module of COMSOL, meshing the post-mining stratum displacement model obtained in S3, and then calculating the deformation of the mining face under the influence of gravity through the solver;

[0011] S5, through the AC / DC module of COMSOL software, select the two-dimensional model, and construct a steady-state direct current electrical detection model based on the thickness of the overburden of the mining face after mining and the resistivity of the overburden of the mining face before mining;

[0012] The thickness of the overburden of the mining face after mining is the difference between the thickness of the overburden of the mining face before mining obtained by S1 and the deformation of the mining face after mining under the influence of gravity.

[0013] Preferably, the mesh quality of the meshes in S2 and S4 is greater than 0.8.

[0014] Preferably, the solver is a direct solver.

[0015] A numerical calculation method for direct current electrical detection of roof of a mining face, comprising:

[0016] A steady-state DC electrical detection model for a mining face is constructed using the method disclosed in the present application; and the DC electrical detection value of the overburden of the mining face is calculated based on the constructed steady-state DC electrical detection model for the mining face.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] (1) The present application discloses a method for constructing a steady-state DC electrical detection model and a calculation method for a mining face. The COMSOL numerical calculation software is used to simulate the deformation of the roof overburden of the mining face to form a geometric deformation characteristic curve of the overburden after deformation. Under the constraints of the geometric deformation characteristic curve, a DC electrical detection numerical calculation model is established, which closely combines the mine DC electrical detection with the disturbance caused by coal mining, thereby improving the reliability of the numerical calculation results.

[0019] (2) The present application discloses a method for constructing a steady-state DC electrical detection model for a mining face and a calculation method. According to the actual situation of the mining face under study, the bulk modulus, shear modulus, cohesion, internal friction angle, density, resistivity and thickness of the overburden are collected, and the deformation simulation of the roof overburden is established using the solid mechanics module of the COMSOL numerical calculation software. A geometric deformation characteristic curve of the deformed overburden is formed in the post-processing function of COMSOL, and the geometric deformation characteristic curve is derived. Under the constraint of the geometric deformation characteristic curve, a geometric model for numerical calculation of DC electrical detection is established in the AC / DC module of COMSOL, which closely combines the mine DC electrical detection with the disturbance caused by coal mining, thereby improving the reliability of the numerical calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 It is a schematic diagram of the deformation model of the roof overburden with three layers of overburden.

[0022] Figure 2 yes Figure 1 The geometric model after meshing.

[0023] Figure 3 This is the displacement diagram of the overburden after 100m of mining.

[0024] Figure 4 It is the geometric deformation characteristic curve of the overburden rock.

[0025] Figure 5 It is the grid generation result of DC electrical detection constrained by the geometric deformation of the overburden rock.

[0026] Figure 6 is the accuracy distribution of DC electrical detection. DETAILED DESCRIPTION

[0027] The invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the invention.

[0028] All components and devices in the present invention, unless otherwise specified, are components and devices known in the prior art.

[0029] COMSOL disclosed in this application refers to COMSOL Multiphysics developed by COMSOL, which is a high-performance simulation software. For details, please refer to the official website https: / / cn.comsol.com /

[0030] Example

[0031] This embodiment takes the numerical calculation of the direct current method for detecting the roof of a three-layer overburden mining face as an example, and explains the present invention in detail in combination with the accompanying drawings and specific implementation methods.

[0032] S1, obtain the bulk modulus, shear modulus, cohesion, internal friction angle, density, resistivity and thickness of the overburden of the mining face before mining, see Table 1, and construct the roof overburden deformation model through the solid mechanics module of COMSOL, as shown in Figure 1 As shown;

[0033] Table 1 Parameters of overburden rock at the mining face before mining

[0034]

[0035] S2, set boundary conditions and peripheral conditions in the solid mechanics module of COMSOL, and mesh the roof overburden deformation model obtained in S1, as shown in Figure 2 As shown, the deformation of the mining face under the influence of gravity before mining is calculated by the solver to obtain the deformation mesh model;

[0036] The boundary condition disclosed in this embodiment is set as the bottom boundary U=0; the peripheral condition adopts roller support constraint for infinite formation model, and the normal displacement of the peripheral boundary is set to 0, U·n=0, n represents the unit vector in the normal direction; the gravity influence is that the vertical acceleration is the gravity acceleration, and the solver selects the direct solver.

[0037] The embodiment disclosed herein meshes the roof overburden deformation model obtained in S1, and checks the mesh quality in the COMSOL software post-processing module to control the mesh quality to be greater than 0.8, otherwise meshes are re-meshed until the mesh quality is greater than 0.8.

[0038] S3, setting the goaf area at the lower part of the deformed grid model obtained in S2 to obtain the post-mining stratum displacement model;

[0039] This embodiment takes the numerical calculation process of roof DC electrical detection when the working face is mined for 100 m as an example, the goaf area is represented by air, and the corresponding initial physical medium parameters of the area adopt vacuum physical medium parameters.

[0040] S4, set the soil plasticity constraint condition and Mohr-Coulomb criterion in the solid mechanics module of COMSOL, mesh the stratum displacement model after mining obtained in S3, and then use the solver to calculate the deformation of the mining face under the influence of gravity after mining, that is, to obtain the displacement of the overburden when the working face is mined for 100m, as shown in Figure 3 As shown; at this time, select the two-dimensional curve drawing in the post-processing module of COMSOL software, set the drawing object to the vertical displacement of the upper boundary of overburden 1, overburden 2 and overburden 3, and obtain Figure 4 .

[0041] The soil plasticity constraint conditions and Mohr-Coulomb criterion can be found in [1] Zhao Chunhu, Jin Dewu, Wang Hao, et al. Construction of overburden damage deformation and aquifer dehydration model in deep coal seam mining in Yushen mining area [J]. Journal of China Coal Society, 2019, 44(07): 2227-2235.

[0042] S5, through the AC / DC module of COMSOL software, select the two-dimensional model, and construct a steady-state direct current electrical detection model through the thickness of the overburden of the mining working face after mining and the resistivity of the overburden of the mining working face before mining; the thickness of the overburden of the mining working face after mining is the difference between the thickness of the overburden of the mining working face before mining obtained by S1 and the deformation of the mining working face after mining under the influence of gravity.

[0043] This embodiment takes a monopole-monopole direct current method device as an example, and sets 20 receiving electrodes at equal intervals of 10m. According to the above method, the COMSOL post-processing function is used to calculate the response voltage (direct current method detection value) of each receiving electrode. Figure 6 The calculation results of the present invention taking into account terrain subsidence and the calculation results of the traditional method without taking into account terrain subsidence are plotted in the figure. It can be seen intuitively that terrain subsidence has a significant impact on the numerical calculation results of DC electrical detection of the roof of the mining face. The calculation method proposed in the present invention effectively improves the reliability of the numerical calculation results.

[0044] From the above description, it can be known that the present invention loads the influence of the mechanical parameters of the overlying surrounding rock on the displacement of the rock formation into the numerical simulation calculation of the DC electrical detection of the roof of the mining face. The simulation process fully considers the bulk modulus, shear modulus, cohesion, internal friction angle, density, resistivity and thickness parameters of the overburden rock. The solid mechanics module of the COMSOL numerical calculation software is used to establish the deformation simulation of the roof overburden rock. The geometric deformation characteristic curve of the deformed overburden rock is formed in the post-processing function of COMSOL, and the geometric deformation characteristic curve is derived. Under the constraint of the geometric deformation characteristic curve, a geometric model of the numerical calculation of the DC electrical detection is established in the AC / DC module of COMSOL, and the mine DC electrical method is closely combined with the disturbance of coal mining, thereby improving the reliability of the numerical calculation results.

[0045] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0047] In addition, the various different implementation modes disclosed in this solution may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the content invented by the present disclosure.

Claims

1. A method for constructing a steady-state direct current electrical detection model for a mining face, characterized in that: The steps include: S1, obtain the bulk modulus, shear modulus, cohesion, internal friction angle, density, resistivity and thickness of the overburden rock of the mining face before mining, and construct the roof overburden deformation model through the solid mechanics module of COMSOL; S2, setting boundary conditions and peripheral conditions in the solid mechanics module of COMSOL, meshing the roof overburden deformation model obtained in S1, and then using the solver to calculate the deformation of the mining face under the influence of gravity before mining to obtain a deformation mesh model; S3, setting the goaf area at the lower part of the deformed grid model obtained in S2 to obtain the post-mining stratum displacement model; S4, setting the soil plasticity constraint condition and Mohr-Coulomb criterion in the solid mechanics module of COMSOL, meshing the post-mining stratum displacement model obtained in S3, and then calculating the deformation of the mining face under the influence of gravity through the solver; S5, through the AC / DC module of COMSOL software, select the two-dimensional model, and construct a steady-state direct current electrical detection model based on the thickness of the overburden of the mining face after mining and the resistivity of the overburden of the mining face before mining; The thickness of the overburden of the mining working face after mining is the difference between the thickness of the overburden of the mining working face before mining obtained by S1 and the deformation of the mining working face after mining under the influence of gravity.

2. The method for constructing a steady-state direct current electrical detection model for a mining face according to claim 1, characterized in that: The mesh quality of the meshes in S2 and S4 is greater than 0.

8.

3. The method for constructing a steady-state direct current electrical detection model for a mining face according to claim 1, characterized in that: The solver is a direct solver.

4. A numerical calculation method for direct current electrical detection of the roof of a mining face, characterized in that: include: Use the method described in any one of claims 1 to 3 to construct a steady-state direct current electrical detection model for the mining face; The DC electrical detection value of the overburden of the mining face is calculated based on the constructed steady-state DC electrical detection model of the mining face.

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