A method for generating initial stress of coal-bearing strata and tunnels in PFC3D

Abstract

The present invention discloses a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, including: obtaining the ground stress parameters of the research block location and the macroscopic basic physical and mechanical parameters corresponding to the coal body and the rock mass, and calibrating the parameters through the PFC3D triaxial compression numerical simulation technology; preliminarily establishing the PFC3D coal-bearing strata numerical model according to the microscopic mechanical parameters and stratum size corresponding to the coal body and the rock mass, and preloading through the wall servo; establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, and generating the coupling surface of the PFC‑FLAC calculation, setting the constitutive model and material parameters corresponding to the coal body and the rock mass at the FLAC3D model area boundary; assigning ground stress to the coal body and the rock mass at the FLAC3D model area boundary and setting the boundary conditions of the model, performing equilibrium calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generating a three-dimensional model of the coal tunnel according to the tunnel size excavation calculation. The present invention realizes the accurate generation of the initial stress of the coal-bearing strata and the tunnel.

Description

Technical Field

[0001] The invention relates to the technical field of numerical simulation experiments, and in particular to a method for generating initial stress of coal-bearing strata and tunnels in PFC3D. Background Art

[0002] The numerical calculation method of discrete element based on PFC3D (a three-dimensional particle fluid simulation software) can well simulate the process of discontinuous deformation and microscopic destruction, and has been widely used in complex coal and rock tunnel mechanics problems. In order to use PFC3D to calculate the coal tunnel engineering case, the user first needs to perform three-dimensional modeling and set model parameter conditions, then perform the initial stress balance calculation of the model according to the ground stress conditions, and finally perform excavation balance calculation to generate a three-dimensional model of the coal tunnel.

[0003] At present, PFC3D usually uses the servo balance method of wall units to calculate the initial stress application process. This method has a good initial stress simulation effect in homogeneous materials. However, due to the large difference in material parameters of coal and rock in actual engineering, especially the elastic modulus of coal is much smaller than that of rock, this will lead to a large difference in the initial stress generation results of coal and rock in coal-bearing strata, thus affecting the accuracy of the three-dimensional model generation of coal roadways. At the same time, some users use the particle membrane method for flexible triaxial loading. Due to the relatively small elastic modulus of the particle membrane, the particle membrane will have a large deformation under this method, which also fails to achieve the effect of initial stress simulation application, and will also affect the generation of the three-dimensional model of coal roadways.

[0004] Since the generation of the three-dimensional model of the coal roadway and the subsequent dynamic load disturbance and other working condition analyses are all based on the initial stress balance, if the initial stress generation results of the coal formation are inaccurate, it will seriously affect the subsequent coal roadway failure mode and analysis and calculation results.

[0005] Therefore, the prior art needs to be improved. Summary of the invention

[0006] The technical problem to be solved by the present invention is that, in view of the defects of the prior art, the present invention provides a method for generating initial stress for coal-bearing strata and tunnels in PFC3D, so as to solve the problem of poor accuracy of the initial stress generation results for coal-bearing strata and tunnels by the existing stress balance method in PFC3D.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] In a first aspect, the present invention provides a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, comprising:

[0009] Obtain the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock mass, and calibrate the parameters through PFC3D triaxial compression numerical simulation technology;

[0010] According to the corresponding micromechanical parameters of coal and rock mass and the formation size, a preliminary PFC3D coal-bearing formation numerical model was established, and preloading was performed through the wall servo.

[0011] Establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generating the coupling surface of PFC-FLAC calculation, and setting the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary;

[0012] The coal and rock bodies at the boundary of the FLAC3D model area are assigned ground stress and the boundary conditions of the model are set. The entire numerical model is balanced and calculated to generate the initial stress of the coal-bearing strata. The three-dimensional model of the coal roadway is generated by excavation calculation and solution according to the roadway size.

[0013] In one implementation, the geostress parameters of the research block location include: the magnitude and azimuth of the first principal stress, the magnitude and azimuth of the second principal stress, and the magnitude and azimuth of the third principal stress;

[0014] The macroscopic basic physical and mechanical parameters corresponding to the coal mass and the rock mass include: elastic modulus, Poisson's ratio, compressive strength, tensile strength, density, internal friction angle and cohesive force.

[0015] In one implementation, the parameter calibration using the PFC3D triaxial compression numerical simulation technology includes:

[0016] Select the particle size corresponding to the coal and rock mass according to the computing power of the computing equipment and the factors affecting the accuracy of the calculation results;

[0017] The PFC3D triaxial compression numerical model is established based on the parallel bonding contact constitutive model, and the macroscopic and microscopic parameter conversion relationships corresponding to the particle size are obtained by trial and error method and linear regression method;

[0018] The microscopic mechanical parameters corresponding to the coal and rock mass are determined according to the macroscopic and microscopic parameter conversion relationship; wherein the microscopic mechanical parameters corresponding to the coal and rock mass include: effective contact modulus, stiffness ratio, parallel bond strength, internal friction angle and friction coefficient.

[0019] In one implementation, the PFC3D coal-bearing stratum numerical model is initially established according to the microscopic mechanical parameters and stratum dimensions corresponding to the coal and rock mass, and preloading is performed through the wall servo, including:

[0020] Generate corresponding coal particles and rock particles according to the stratum size, and preliminarily establish the PFC3D coal-bearing stratum numerical model;

[0021] The group names corresponding to the coal seams and rock strata are respectively set by grouping commands, and cementation is applied to the PFC3D coal-bearing stratum numerical model according to the microscopic mechanical parameters corresponding to the coal bodies and rock bodies, and the gravity acceleration parameters corresponding to the PFC3D coal-bearing stratum numerical model are set;

[0022] The wall servo is used to preload the PFC3D coal-bearing stratum numerical model to the value of the third principal stress, and the displacement and velocity of all particles are reset to zero.

[0023] In one implementation, the establishing of the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generating a coupling surface for PFC-FLAC calculation, and setting the constitutive model and material parameters corresponding to the coal and rock mass at the FLAC3D model area boundary include:

[0024] Divide the structural unit grids corresponding to the coal and rock mass according to the computing power of the computing equipment and the factors affecting the accuracy of the calculation results, and establish the FLAC3D model area boundaries of the coal and rock mass structural units;

[0025] According to the wall coupling command, a coupling medium is created on the surface of the structural unit of the spherical particles of the PFC3D coal-bearing stratum numerical model and the boundary of the FLAC3D model area to form the coupling surface of the PFC-FLAC calculation;

[0026] The constitutive model and material parameters corresponding to the coal mass and rock mass at the boundary of the FLAC3D model area are set; wherein the constitutive model and material parameters corresponding to the coal mass and rock mass include: a coal mass constitutive model, a rock mass constitutive model, and Young's modulus, Poisson's ratio, cohesion, tensile strength, internal friction angle and density corresponding to each constitutive model.

[0027] In one implementation, assigning ground stress to coal and rock masses at the boundary of the FLAC3D model region and setting the boundary conditions of the model, performing equilibrium calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, includes:

[0028] The ground stress values ​​corresponding to the coal body and the rock body at the boundary of the FLAC3D model region are set according to the initialization command, and the stress boundary conditions of the same magnitude are applied on the boundary surface of the FLAC3D model region according to the distribution of the ground stress field and kept constant;

[0029] The entire numerical model is balanced by the calculation balance command to generate the initial stress of the coal-bearing strata.

[0030] In one implementation, a three-dimensional model of a coal roadway is generated by calculating and solving the excavation calculation according to the roadway size, including:

[0031] The displacement and velocity of all particles are reset to zero, and the corresponding PFC3D particles and FLAC3D units are deleted according to the cross-sectional shape and size of the roadway. The balance calculation command is used to perform a balance calculation on the entire numerical model to generate a three-dimensional model of the coal roadway.

[0032] In a second aspect, the present invention provides an initial stress generating device for coal-bearing strata and tunnels in PFC3D, comprising:

[0033] The parameter calibration module is used to obtain the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock mass, and calibrate the parameters through the PFC3D triaxial compression numerical simulation technology;

[0034] The numerical model building module is used to preliminarily build the PFC3D coal-bearing stratum numerical model according to the corresponding microscopic mechanical parameters of the coal and rock mass and the stratum size, and to perform preloading through the wall servo;

[0035] A coupling surface establishment module is used to establish the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generate the coupling surface of the PFC-FLAC calculation, and set the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary;

[0036] The balance calculation module is used to assign ground stress to the coal and rock masses at the boundary of the FLAC3D model area and set the boundary conditions of the model, perform balance calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generate a three-dimensional model of the coal roadway based on the excavation calculation and solution of the roadway size.

[0037] In a third aspect, the present invention provides a terminal, comprising: a processor and a memory, wherein the memory stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D, and when the initial stress generation program for coal-bearing strata and tunnels in PFC3D is executed by the processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described in the first aspect.

[0038] In a fourth aspect, the present invention further provides a medium, which is a computer-readable storage medium, and which stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D. When the initial stress generation program for coal-bearing strata and tunnels in PFC3D is executed by a processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described in the first aspect.

[0039] The present invention adopts the above technical solution to achieve the following effects:

[0040] (1) The present invention takes into account both computational efficiency and modeling precision through coupled modeling, ensures the deformation coordination of the embedded particle model and the external finite difference grid model, and provides a new modeling idea for the three-dimensional coal seam tunnel modeling method.

[0041] (2) The present invention can quickly and effectively achieve the equilibrium simulation of the initial stress of coal-bearing strata by preloading the particle model, setting the ground stress value for the unit model, and applying the stress boundary on the model surface.

[0042] (3) The present invention can achieve uniform initial stress distribution in the coal body and rock body through the uneven deformation of the coupling surface, and realize accurate generation of the initial stress field of the coal-bearing strata in PFC3D, which is more in line with the stress simulation of actual deep-buried coal mine engineering.

[0043] (4) The three-dimensional model of coal roadway generated by the present invention can achieve the effects of local stress concentration, discontinuous deformation and destruction, and can remove the boundary effect of the particle model. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0045] Figure 1 It is a flow chart of the method for generating initial stress of coal-bearing strata and tunnels in PFC3D of the present invention.

[0046] Figure 2 It is a schematic diagram of the coal body and rock mass parameter calibration curve diagram in the present invention.

[0047] Figure 3 It is a schematic diagram of initial stress monitoring data of coal-bearing strata with conventional wall servo loading in the present invention.

[0048] Figure 4 It is a schematic cross-sectional view of the geometric model of the three-dimensional coal-bearing strata in the present invention.

[0049] Figure 5 It is a schematic diagram of the initial stress monitoring data of the coal-bearing strata in the present invention.

[0050] Figure 6 It is a schematic diagram of the geometric model of the coal roadway in the present invention.

[0051] Figure 7 It is a functional principle diagram of a terminal in one implementation of the present invention.

[0052] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] Exemplary Methods

[0055] At present, PFC3D usually uses the servo balance method of wall units to calculate the initial stress application process. This method has a good initial stress simulation effect in homogeneous materials. However, due to the large difference in material parameters of coal and rock in actual engineering, especially the elastic modulus of coal is much smaller than that of rock, this will lead to a large difference in the initial stress generation results of coal and rock in coal-bearing strata, thus affecting the accuracy of the three-dimensional model generation of coal roadways. At the same time, some users use the particle membrane method for flexible triaxial loading. Due to the relatively small elastic modulus of the particle membrane, the particle membrane will have a large deformation under this method, which also fails to achieve the effect of initial stress simulation application and will also affect the generation of the three-dimensional model of coal roadways.

[0056] Since the generation of three-dimensional coal roadway models and subsequent dynamic load disturbance and other working condition analyses are all based on the premise of initial stress balance, if the initial stress generation results of coal-bearing strata are of poor accuracy, it will seriously affect the subsequent failure mode of coal roadways and the results of analysis and calculation. In response to the above technical problems, an embodiment of the present invention provides a method for generating initial stress of coal-bearing strata and roadways in PFC3D. This method obtains the ground stress parameters of the study block location and the macroscopic basic physical and mechanical parameters corresponding to the coal body and rock mass, and calibrates the parameters through the PFC3D triaxial compression numerical simulation technology; preliminarily establishes a PFC3D coal-bearing stratum numerical model based on the microscopic mechanical parameters and stratum dimensions corresponding to the coal body and rock mass, and performs preloading through the wall servo; establishes the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, and generates the PFC- The coupling surface of FLAC calculation is used to set the constitutive model and material parameters corresponding to the coal body and rock mass at the boundary of the FLAC3D model area; the ground stress is assigned to the coal body and rock mass at the boundary of the FLAC3D model area and the boundary conditions of the model are set, the initial stress of the coal-bearing stratum is generated by equilibrium calculation of the entire numerical model, and the three-dimensional model of the coal roadway is generated by excavation calculation and solution according to the size of the roadway; therefore, the embodiment of the present invention can achieve uniform initial stress distribution in the coal body and rock body, and realize accurate generation of initial stress of coal-bearing strata and roadways in PFC3D, which is more in line with the stress simulation of actual deep-buried coal mine engineering.

[0057] like Figure 1As shown, an embodiment of the present invention provides a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, comprising the following steps:

[0058] Step S100, obtaining the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock masses, and calibrating the parameters through the PFC3D triaxial compression numerical simulation technology.

[0059] In this embodiment, the initial stress of coal-bearing strata and tunnels is accurately generated based on PFC3D (a three-dimensional particle fluid simulation software). Before three-dimensional modeling is performed through PFC3D, it is necessary to collect the ground stress parameters of the study block location and the macroscopic basic physical and mechanical parameters of the coal and rock masses.

[0060] Due to the complexity and variability of the ground stress state, there are differences in the ground stress state at different points in the same mine. The ground stress data of the coal roadway in the study area include but are not limited to: the magnitude and azimuth of the maximum principal stress (i.e. the magnitude and azimuth of the first principal stress), the magnitude and azimuth of the intermediate principal stress (i.e. the magnitude and azimuth of the second principal stress) and the magnitude and azimuth of the minimum principal stress (i.e. the magnitude and azimuth of the third principal stress).

[0061] As an example, the maximum principal stress in the study block in this embodiment is horizontal stress, with a value of approximately 26 MPa and a direction of 79.98° to 82.87°; the azimuths of the intermediate principal stresses are concentrated at 327.25° to 347.94°, with a value of approximately 17 MPa; the azimuths of the minimum principal stresses are concentrated at 169.85° to 175.78°, with a stress value of 14 MPa; and the vertical stress is 17 MPa.

[0062] In this embodiment, the macroscopic basic physical and mechanical parameters corresponding to the coal mass and rock mass are mainly used to obtain the macroscopic mechanical parameters of the top and bottom rock layers and coal seams in the study area, including but not limited to: elastic modulus, Poisson's ratio, compressive strength, tensile strength, density, internal friction angle and adhesion.

[0063] Since a five-layer rock model is often constructed in the field of coal mining, namely the basic roof, the direct roof, the coal seam, the direct bottom and the basic bottom, this embodiment needs to obtain the macroscopic basic physical and mechanical parameters of these five rock layers. The macroscopic mechanical parameters of the representative coal rock in this block are shown in Table 1.

[0064] Table 1 Macroscopic mechanical parameters of representative coal rocks

[0065]

[0066] In this embodiment, after obtaining the ground stress parameters of the study block location and the macroscopic basic physical and mechanical parameters corresponding to the coal and rock masses, the parameters can be calibrated through the PFC3D triaxial compression numerical simulation technology, thereby realizing the conversion between the macroscopic parameters and microscopic parameters corresponding to the coal and rock masses.

[0067] Specifically, in an implementation of this embodiment, step S100 includes the following steps:

[0068] Step S101, selecting particle sizes corresponding to coal and rock masses according to the computing power of the computing equipment and factors affecting the accuracy of the calculation results;

[0069] Step S102, establishing the PFC3D triaxial compression numerical model based on the parallel bonding contact constitutive model, and using trial and error method and linear regression method to obtain the macroscopic and microscopic parameter conversion relationship corresponding to the particle size;

[0070] Step S103, determining the microscopic mechanical parameters corresponding to the coal mass and the rock mass according to the macroscopic and microscopic parameter conversion relationship.

[0071] In this embodiment, in the process of parameter calibration through PFC3D triaxial compression numerical simulation technology, it is first necessary to comprehensively consider the computer's computing power and the factors affecting the accuracy of the calculation results, and select a reasonable particle size, where the particle size includes the particle size corresponding to coal particles and rock particles; if the particles are too small, the calculation efficiency will be reduced, and if the particles are too large, the accuracy of the calculation results will be reduced.

[0072] In this regard, in this embodiment, a PFC3D triaxial compression numerical model is established based on a parallel bonding contact constitutive model, and the trial and error method and linear regression method are used to obtain the macro- and micro-parameter conversion relationship corresponding to the particle size; then, the micro-mechanical parameters corresponding to the coal body and the rock mass can be determined according to the macro- and micro-parameter conversion relationship; wherein, the micro-mechanical parameters corresponding to the coal body and the rock mass include but are not limited to: effective contact modulus, stiffness ratio, parallel bonding strength, internal friction angle and friction coefficient.

[0073] Specifically, the focus of the simulation and analysis through the PFC3D triaxial compression numerical simulation technology is the situation around the coal-rock tunnel. The PFC3D coal-bearing stratum only needs to establish a three-layer surrounding rock numerical model. Therefore, the PFC3D parameter calibration only needs to consider the microscopic parameters of the direct roof and floor rock layers and coal seams.

[0074] As an example, considering the computing power of the computer and the accuracy of the calculation results, the minimum radius of the particles in this embodiment is 0.1m, and the radius ratio is 1.5. The PFC3D triaxial compression numerical model is established based on the parallel bonding contact constitutive model, and the macro-micro parameter conversion relationship corresponding to the particle size is obtained by trial and error method and linear regression method. The specific coal and rock particle micro parameters are shown in Table 2, and the coal and rock mass parameter calibration curve is shown in Figure 2 shown.

[0075] Table 2 Coal rock calibration microscopic parameters

[0076]

[0077] By comparing Table 1 with the calibration curve, it can be seen that the calibrated mechanical properties of coal rock are consistent with the macroscopic parameters of coal rock, indicating the rationality of the mesoscopic parameters of numerical simulation.

[0078] like Figure 1 As shown, an embodiment of the present invention provides a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, comprising the following steps:

[0079] Step S200, preliminarily establish a PFC3D coal-bearing stratum numerical model according to the microscopic mechanical parameters and stratum dimensions corresponding to the coal and rock masses, and perform preloading through the wall servo.

[0080] In this embodiment, after calibrating the corresponding microscopic mechanical parameters of the coal and rock masses, coal particles and rock particles are generated according to the size of the coal-rock strata, a three-dimensional numerical model of the coal-bearing strata is established, and preloading is performed through the wall servo.

[0081] Specifically, in an implementation of this embodiment, step S200 includes the following steps:

[0082] Step S201, generating corresponding coal particles and rock particles according to the stratum size, and preliminarily establishing the PFC3D coal-bearing stratum numerical model;

[0083] Step S202, respectively setting the group names corresponding to the coal seam and the rock stratum through the grouping command, applying cementation to the PFC3D coal-bearing stratum numerical model according to the microscopic mechanical parameters corresponding to the coal body and the rock body, and setting the gravity acceleration parameters corresponding to the PFC3D coal-bearing stratum numerical model;

[0084] Step S203, using the wall servo to preload the PFC3D coal-bearing stratum numerical model to the value of the third principal stress, and clearing the displacement and velocity of all particles to zero.

[0085] In this embodiment, corresponding coal particles and rock particles are generated according to the formation size, and the PFC3D coal-bearing formation numerical model is preliminarily established. Then, the group command (i.e., the grouping command, used to create groups) is used to set different group names for the coal seams and rock strata, and cementation is applied to the PFC3D coal-bearing formation numerical model according to the corresponding micromechanical parameters of the coal body and the rock mass.

[0086] It can be understood that the coordinate system in this embodiment is defined as follows: the z-axis is agreed to be the plumb direction, the x-direction perpendicular to the roadway direction is the horizontal tangent direction, and the y-direction parallel to the roadway direction is the horizontal radial direction. After applying cementation to the PFC3D coal-bearing stratum numerical model, the component of the gravity acceleration of the particles along the horizontal direction is set to 0, and the component along the plumb direction is set to 9.8 m / s 2 , pointing downward.

[0087] As an example, when preliminarily establishing a PFC3D coal-bearing stratum numerical model, a three-dimensional three-layer coal rock model can be established in PFC3D, and the group names of the three rock layers from top to bottom are immediate roof, coal, and immediate floor; the overall size of the PFC3D coal-bearing stratum numerical model is 10m×10m×10m, and the thickness from top to bottom is 4m, 3m and 3m respectively, the minimum radius of the particle is 0.1m, the radius ratio is 1.5, and the model contains a total of 99422 particles.

[0088] According to the microscopic mechanical parameters of the coal and rock mass calibrated in step S103, the PFC3D coal-bearing stratum numerical model is cemented, and the component of the gravity acceleration of the corresponding particles along the plumb bob direction is set to 9.8 m / s. 2 , pointing downward. According to the ground stress parameters of the coal roadway at the location of the study block, the maximum principal stress at the location of the study block is perpendicular to the direction of the roadway, and the initial stress should be 26MPa, the intermediate principal stress is vertical stress, and the initial stress should be 17MPa, and the minimum principal stress is parallel to the direction of the roadway, and the initial stress should be 14MPa.

[0089] Furthermore, after setting the gravity acceleration parameters corresponding to the PFC3D coal-bearing stratum numerical model, the wall unit servo preload is used to load to the value of the minimum principal stress (i.e., the third principal stress). This method can not only release the large internal stress inside the model, but also reduce the time for subsequent initial stress loading balance. In order to avoid the influence of particle velocity on subsequent coupling, the particle displacement and velocity need to be cleared after the model preload balance.

[0090] As an example, in the process of preloading by wall servo in this embodiment, the conventional wall servo method is firstly adopted. Since the stress monitoring of PFC3D model is usually carried out by using a measuring ball, the radius of the measuring ball in this embodiment is 0.4m, and three measuring balls are respectively set at the center of the top and bottom rock layers and the coal seam. After the model is balanced, the initial stress monitoring data of the coal and rock bodies in the coal-bearing strata of the measuring balls are as follows: Figure 3 As shown, the measuring balls 1, 2 and 3 are the measuring balls of the roof rock layer, coal seam and bottom rock layer respectively. Figure 3 It can be seen that only the vertical stress generation in the coal body and rock mass meets the actual ground stress conditions, and the horizontal stress in the rock mass is much higher than that in the coal body.

[0091] like Figure 1 As shown, an embodiment of the present invention provides a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, comprising the following steps:

[0092] Step S300, establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generating a coupling surface for PFC-FLAC calculation, and setting the constitutive model and material parameters corresponding to the coal and rock masses at the FLAC3D model area boundary.

[0093] In this embodiment, the FLAC3D software (a simulation calculation software) embedded in PFC3D is used to establish a finite difference grid, and a zone (the basic unit of FLAC3D software) unit is generated on the periphery of the PFC3D particle model as a zone boundary to ensure that the size of the embedded particle model matches the size of the internal airspace of the finite difference grid. When establishing the finite difference grid, the computing power of the computer and the factors affecting the accuracy of the calculation results are comprehensively considered, and a reasonable grid size is selected; if the grid is divided too small, the calculation efficiency will be reduced, and if the grid is divided too large, the accuracy of the calculation results will be reduced.

[0094] Since PFC3D always runs in large strain mode, it is necessary to activate the large strain mode of the structural elements, that is, turn on the model largestrain on command (i.e., the model large strain command). In particular, simple meshing can be achieved directly by deleting the internal PFC3D particle calculation area after generating zone units in FLAC3D, and complex meshing can be achieved by modeling in third-party software and then importing it into FLAC3D software.

[0095] Specifically, in an implementation of this embodiment, step S300 includes the following steps:

[0096] Step S301, dividing the structural unit grids corresponding to the coal body and the rock body according to the computing power of the computing equipment and the factors affecting the accuracy of the calculation results, and establishing the FLAC3D model area boundaries of the coal body and the rock body structural units;

[0097] Step S302, creating a coupling medium on the surface of the structural unit at the boundary of the spherical particles of the PFC3D coal-bearing stratum numerical model and the FLAC3D model region according to the wall coupling command, to form a coupling surface for the PFC-FLAC calculation;

[0098] Step S303, setting the constitutive model and material parameters corresponding to the coal mass and rock mass at the boundary of the FLAC3D model area; wherein the constitutive model and material parameters corresponding to the coal mass and rock mass include: coal mass constitutive model, rock mass constitutive model, and Young's modulus, Poisson's ratio, cohesion, tensile strength, internal friction angle and density corresponding to each constitutive model.

[0099] In this embodiment, FLAC3D is used to establish the regional boundaries of coal-bearing strata. Specifically, PFC3D is the main control program, which calls the function library of FLAC3D to achieve platform integration, thereby providing a unified analysis platform for continuous-discontinuous coupling analysis technology. Therefore, it is first necessary to load it through the tools load flac3d (FLAC3D embedded tool) menu item in the user interface.

[0100] Considering that the grid division of this embodiment is relatively simple, a three-dimensional five-layer rock model can be directly created in sequence. The group names of the five rock layers from top to bottom are main roof, immediate roof, coal, immediate floor and main floor. The overall size of the model is 20m×20m×20m, and the thickness from top to bottom is 5m, 4m, 3m, 3m and 5m respectively. After generating the overall grid unit, the unit of the internal PFC particle calculation area size is deleted to ensure that the size of the embedded particle model matches the internal airspace size of the finite difference grid.

[0101] In this embodiment, in the process of establishing the coupling surface calculated by PFC-FLAC, a coupling medium wall is created on the surface of the spherical particles and the zone unit through the wall-zone create command (i.e., the wall coupling command, the medium creation command) to perform data exchange and transmission, thereby forming the coupling surface calculated by PFC-FLAC. The coupling surface can realize the uneven deformation loading of coal rock. In particular, in order to avoid the inability to form a continuous coupling surface, the skip-errors command can be added to ignore the errors generated by the coupling surface. The geometric model of the three-dimensional coal-bearing strata in this embodiment is as follows: Figure 4 As shown, Figure 4 In order to clearly see the internal model structure, a cross-sectional perspective is used here.

[0102] Furthermore, when setting the constitutive models and material parameters corresponding to the coal and rock masses at the boundary of the FLAC3D model area, the constitutive models corresponding to the coal and rock masses are selected. Considering that there is no major damage in the FLAC3D calculation area, the rock masses all adopt elastic constitutive models, and their parameters are directly input according to the macroscopic parameters of the rock masses in Table 1; specifically, the parameters of each constitutive model include Young's modulus, Poisson's ratio, cohesion, tensile strength, internal friction angle and density.

[0103] This embodiment takes into account both computational efficiency and modeling precision through coupled modeling, ensures deformation coordination between the embedded particle model and the external finite difference grid model, and provides a new modeling idea for the three-dimensional coal seam roadway modeling method.

[0104] like Figure 1 As shown, in one implementation of the embodiment of the present invention, the method for generating initial stress of coal-bearing strata and tunnels in PFC3D further includes the following steps:

[0105] Step S400, assigning ground stress to the coal and rock masses at the boundary of the FLAC3D model area and setting the boundary conditions of the model, performing equilibrium calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generating a three-dimensional model of the coal roadway by excavation calculation and solution according to the roadway size.

[0106] In this embodiment, the model ground stress value can be set and the stress boundary can be applied on the model surface through the initial command (i.e., the initialization command, the command for setting the initial state), which can effectively realize the stress application simulation of the tectonic stress field.

[0107] Specifically, in an implementation of this embodiment, step S400 includes the following steps:

[0108] Step S401, setting the ground stress values ​​corresponding to the coal and rock masses at the boundary of the FLAC3D model area according to the initialization command, and applying the same magnitude of stress boundary conditions on the boundary surface of the FLAC3D model area according to the distribution of the ground stress field and keeping them constant.

[0109] As an example in this embodiment, the initial command is first used to set the ground stress values ​​corresponding to the coal body and rock body at the boundary of the FLAC3D model area, wherein the initial stress in the x direction should be 26MPa, the initial stress in the y direction should be 14MPa, and the initial stress in the z direction should be 17MPa; then, according to the distribution of the ground stress field, stress boundary conditions of the same magnitude are applied to the surface of the boundary of the FLAC3D model area and kept constant. In this process, the constitutive model does not set velocity boundary conditions, so the stress boundary applied on the surface of the constitutive model can be considered as the stress received by the outermost unit of the constitutive model. Finally, the component of the unit's gravity acceleration in the horizontal direction is set to 0, and the component in the vertical direction is set to 9.8m / s2 , pointing downward.

[0110] Specifically, in an implementation of this embodiment, step S400 further includes the following steps:

[0111] Step S402, performing equilibrium calculation on the entire numerical model through a calculation equilibrium command to generate the initial stress of the coal-bearing stratum;

[0112] Step S403, reset the displacement and velocity of all particles, delete the corresponding PFC3D particles and FLAC3D units according to the shape and size of the roadway section, and perform a balance calculation on the entire numerical model through the calculation balance command to generate a three-dimensional model of the coal roadway.

[0113] In this embodiment, the balance calculation of the entire model specifically includes: using the model solve command (i.e., the calculation balance command, the model solving command) to balance the entire model. The balance result can be considered as the result of the superposition of the tectonic stress field and the self-weight stress field, thereby realizing the generation of the initial stress field of the coal-bearing strata. Since the FLAC3D model has no displacement boundary conditions, the regional boundaries may produce large displacements during the balance process, so it is necessary to clear all node velocities after the model reaches balance. In particular, when the number of particles and units exceeds a certain amount, it will make balance difficult, so the balance conditions can be reduced, and the unbalanced force reaches 1×10 -4 It can be considered that the equilibrium stop condition has been reached. The initial stress monitoring data of coal and rock in the coal-bearing strata of the measuring ball after the model is balanced are as follows: Figure 5 As shown, by comparing with the traditional wall servo method, it can be seen that the method of the present invention can achieve uniform initial stress distribution in the coal body and the rock body, and both the horizontal stress and the vertical stress meet the actual initial stress conditions.

[0114] Furthermore, in this embodiment, the calculation and solution according to the tunnel size specifically includes: according to the tunnel cross-sectional shape and size, the ball delete command and the zone delete command are used to delete the PFC3D particles and the FLAC3D units respectively to realize the tunnel excavation, and then the balance calculation of the whole model is performed to generate a three-dimensional model of the coal tunnel.

[0115] In this embodiment, the cross-section of the roadway is rectangular, and the cross-section size is 3m×3m. First, in order to avoid the influence of particle velocity on excavation, the model needs to clear the particle displacement and velocity. Then, the ball delete command (i.e., ball particle delete command) and zone delete command (i.e., unit delete command) are used to delete PFC3D particles and FLAC3D units respectively to realize roadway excavation. Finally, the whole model is balanced and calculated. The generated three-dimensional model of the coal roadway is as follows: Figure 6 shown.

[0116] This embodiment achieves the following technical effects through the above technical solution:

[0117] (1) The present invention takes into account both computational efficiency and modeling precision through coupled modeling, ensures the deformation coordination of the embedded particle model and the external finite difference grid model, and provides a new modeling idea for the three-dimensional coal seam tunnel modeling method.

[0118] (2) The present invention can quickly and effectively achieve the equilibrium simulation of the initial stress of coal-bearing strata by preloading the particle model, setting the ground stress value for the unit model, and applying the stress boundary on the model surface.

[0119] (3) The present invention can achieve uniform initial stress distribution in the coal body and rock body through the uneven deformation of the coupling surface, and realize accurate generation of the initial stress field of the coal-bearing strata in PFC3D, which is more in line with the stress simulation of actual deep-buried coal mine engineering.

[0120] (4) The three-dimensional model of coal roadway generated by the present invention can achieve the effects of local stress concentration, discontinuous deformation and destruction, and can remove the boundary effect of the particle model.

[0121] Exemplary Devices

[0122] Based on the above embodiments, the present invention further provides an initial stress generating device for coal-bearing strata and tunnels in PFC3D, comprising:

[0123] The parameter calibration module is used to obtain the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock mass, and calibrate the parameters through the PFC3D triaxial compression numerical simulation technology;

[0124] The numerical model building module is used to preliminarily build the PFC3D coal-bearing stratum numerical model according to the corresponding microscopic mechanical parameters of the coal and rock mass and the stratum size, and to perform preloading through the wall servo;

[0125] A coupling surface establishment module is used to establish the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generate the coupling surface of the PFC-FLAC calculation, and set the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary;

[0126] The balance calculation module is used to assign ground stress to the coal and rock masses at the boundary of the FLAC3D model area and set the boundary conditions of the model, perform balance calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generate a three-dimensional model of the coal roadway based on the excavation calculation and solution of the roadway size.

[0127] This embodiment achieves the following technical effects through the above technical solution:

[0128] (1) The present invention takes into account both computational efficiency and modeling precision through coupled modeling, ensures the deformation coordination of the embedded particle model and the external finite difference grid model, and provides a new modeling idea for the three-dimensional coal seam tunnel modeling method.

[0129] (2) The present invention can quickly and effectively achieve the equilibrium simulation of the initial stress of coal-bearing strata by preloading the particle model, setting the ground stress value for the unit model, and applying the stress boundary on the model surface.

[0130] (3) The present invention can achieve uniform initial stress distribution in the coal body and rock body through the uneven deformation of the coupling surface, and realize accurate generation of the initial stress field of the coal-bearing strata in PFC3D, which is more in line with the stress simulation of actual deep-buried coal mine engineering.

[0131] (4) The three-dimensional model of coal roadway generated by the present invention can achieve the effects of local stress concentration, discontinuous deformation and destruction, and can remove the boundary effect of the particle model.

[0132] Based on the above embodiment, the present invention further provides a terminal, whose principle block diagram can be as follows: Figure 7 shown.

[0133] The terminal includes: a processor, a memory, an interface, a display screen and a communication module connected through a system bus; wherein the processor of the terminal is used to provide computing and control capabilities; the memory of the terminal includes a storage medium and an internal memory; the storage medium stores an operating system and a computer program; the internal memory provides an environment for the operation of the operating system and the computer program in the storage medium; the interface is used to connect to external devices; the display screen is used to display corresponding information; and the communication module is used to communicate with a cloud server or other devices.

[0134] When the computer program is executed by a processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D.

[0135] It can be understood by those skilled in the art that Figure 7 The principle block diagram shown in the figure is only a block diagram of a partial structure related to the scheme of the present invention, and does not constitute a limitation on the terminal to which the scheme of the present invention is applied. The specific terminal may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0136] In one embodiment, a terminal is provided, which includes: a processor and a memory, wherein the memory stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D, and the initial stress generation program for coal-bearing strata and tunnels in PFC3D is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described above when executed by the processor.

[0137] In one embodiment, a storage medium is provided, wherein the storage medium stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D. When the initial stress generation program for coal-bearing strata and tunnels in PFC3D is executed by a processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described above.

[0138] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the computer program can be stored in a non-volatile storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include non-volatile and volatile memory.

[0139] In summary, the present invention provides a method for generating initial stress of coal-bearing strata and tunnels in PFC3D, including: obtaining the ground stress parameters of the research block location and the macroscopic basic physical and mechanical parameters corresponding to the coal body and the rock mass, and calibrating the parameters through the PFC3D triaxial compression numerical simulation technology; preliminarily establishing the PFC3D coal-bearing strata numerical model according to the microscopic mechanical parameters and stratum size corresponding to the coal body and the rock mass, and preloading through the wall servo; establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, and generating the coupling surface of the PFC-FLAC calculation, setting the constitutive model and material parameters corresponding to the coal body and the rock mass at the FLAC3D model area boundary; assigning ground stress to the coal body and the rock mass at the FLAC3D model area boundary and setting the boundary conditions of the model, performing equilibrium calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generating a three-dimensional model of the coal tunnel according to the tunnel size excavation calculation. The present invention realizes the accurate generation of initial stress of coal-bearing strata and tunnels.

[0140] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for generating initial stress of coal-bearing strata and tunnels in PFC3D, characterized in that: include: Obtain the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock mass, and calibrate the parameters through PFC3D triaxial compression numerical simulation technology; According to the corresponding microscopic mechanical parameters of coal and rock mass and the formation size, a preliminary PFC3D coal-bearing formation numerical model was established, and preloading was performed through the wall servo. Establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generating the coupling surface of PFC-FLAC calculation, and setting the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary; The coal and rock bodies at the boundary of the FLAC3D model area are assigned ground stress and the boundary conditions of the model are set. The entire numerical model is balanced and calculated to generate the initial stress of the coal-bearing strata. The three-dimensional model of the coal roadway is generated by excavation calculation and solution according to the roadway size.

2. The method for generating initial stress of coal-bearing strata and tunnels in PFC3D according to claim 1, characterized in that: The in-situ stress parameters of the research block include: the magnitude and azimuth of the first principal stress, the magnitude and azimuth of the second principal stress, and the magnitude and azimuth of the third principal stress; The macroscopic basic physical and mechanical parameters corresponding to the coal mass and rock mass include: elastic modulus, Poisson's ratio, compressive strength, tensile strength, density, internal friction angle and cohesive force.

3. The method for generating initial stress of coal-bearing strata and tunnels in PFC3D according to claim 1, characterized in that: The parameter calibration is performed by using the PFC3D triaxial compression numerical simulation technology, including: Select the particle size corresponding to the coal and rock mass according to the computing power of the computing equipment and the factors affecting the accuracy of the calculation results; The PFC3D triaxial compression numerical model is established based on the parallel bonding contact constitutive model, and the macroscopic and microscopic parameter conversion relationships corresponding to the particle size are obtained by trial and error method and linear regression method; The microscopic mechanical parameters corresponding to the coal and rock mass are determined according to the macroscopic and microscopic parameter conversion relationship; wherein the microscopic mechanical parameters corresponding to the coal and rock mass include: effective contact modulus, stiffness ratio, parallel bond strength, internal friction angle and friction coefficient.

4. The method for generating initial stress of coal-bearing strata and tunnels in PFC3D according to claim 2, characterized in that: The PFC3D coal-bearing stratum numerical model is initially established according to the microscopic mechanical parameters and stratum dimensions corresponding to the coal and rock mass, and preloading is performed through the wall servo, including: Generate corresponding coal particles and rock particles according to the stratum size, and establish the PFC3D coal-bearing stratum numerical model; The group names corresponding to the coal seams and rock strata are respectively set by grouping commands, and cementation is applied to the PFC3D coal-bearing stratum numerical model according to the microscopic mechanical parameters corresponding to the coal bodies and rock bodies, and the gravity acceleration parameters corresponding to the PFC3D coal-bearing stratum numerical model are set; The PFC3D coal-bearing stratum numerical model is preloaded to the value of the third principal stress by using the wall servo, and the displacement and velocity of all particles are reset to zero.

5. The method for generating initial stress of coal-bearing strata and tunnels in PFC3D according to claim 1, characterized in that: The step of establishing the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generating a coupling surface for PFC-FLAC calculation, and setting the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary includes: Divide the structural unit grids corresponding to the coal and rock mass according to the computing power of the computing equipment and the factors affecting the accuracy of the calculation results, and establish the FLAC3D model area boundaries of the coal and rock mass structural units; According to the wall coupling command, a coupling medium is created on the surface of the structural unit of the spherical particles of the PFC3D coal-bearing stratum numerical model and the boundary of the FLAC3D model area to form the coupling surface of the PFC-FLAC calculation; The constitutive model and material parameters corresponding to the coal mass and rock mass at the boundary of the FLAC3D model area are set; wherein the constitutive model and material parameters corresponding to the coal mass and rock mass include: a coal mass constitutive model, a rock mass constitutive model, and Young's modulus, Poisson's ratio, cohesion, tensile strength, internal friction angle and density corresponding to each constitutive model.

6. The method for generating initial stress of coal-bearing strata and tunnels in PFC3D according to claim 1, characterized in that: The assigning of ground stress to the coal and rock masses at the boundary of the FLAC3D model area and setting the boundary conditions of the model include: The ground stress values ​​corresponding to the coal body and the rock body at the boundary of the FLAC3D model area are set according to the initialization command, and the stress boundary conditions of the same magnitude are applied to the boundary surface of the FLAC3D model area according to the distribution of the ground stress field and kept constant.

7. The method for generating the initial stress of coal-bearing strata and the three-dimensional model of coal roadway in PFC3D according to claim 1 is characterized in that: The method of performing a balance calculation on the entire numerical model to generate the initial stress of the coal-bearing stratum and performing an excavation calculation and solving to generate a three-dimensional model of the coal roadway according to the roadway size includes: The entire numerical model is balanced by the calculation balance command to generate the initial stress of the coal-bearing strata; The displacement and velocity of all particles are reset to zero, and the corresponding PFC3D particles and FLAC3D units are deleted according to the cross-sectional shape and size of the roadway. The balance calculation command is used to perform a balance calculation on the entire numerical model to generate a three-dimensional model of the coal roadway.

8. An initial stress generating device for coal-bearing strata and tunnels in PFC3D, characterized in that: include: The parameter calibration module is used to obtain the ground stress parameters of the research block and the macroscopic basic physical and mechanical parameters of the coal and rock mass, and calibrate the parameters through the PFC3D triaxial compression numerical simulation technology; The numerical model building module is used to preliminarily build the PFC3D coal-bearing stratum numerical model according to the corresponding microscopic mechanical parameters of the coal and rock mass and the stratum size, and to perform preloading through the wall servo; A coupling surface establishment module is used to establish the FLAC3D model area boundary of the PFC3D coal-bearing stratum numerical model, generate the coupling surface of the PFC-FLAC calculation, and set the constitutive model and material parameters corresponding to the coal body and rock mass at the FLAC3D model area boundary; The balance calculation module is used to assign ground stress to the coal and rock masses at the boundary of the FLAC3D model area and set the boundary conditions of the model, perform balance calculation on the entire numerical model to generate the initial stress of the coal-bearing strata, and generate a three-dimensional model of the coal roadway based on the excavation calculation and solution of the roadway size.

9. A terminal, characterized in that: include: A processor and a memory, wherein the memory stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D, and when the initial stress generation program for coal-bearing strata and tunnels in PFC3D is executed by the processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores an initial stress generation program for coal-bearing strata and tunnels in PFC3D. When the initial stress generation program for coal-bearing strata and tunnels in PFC3D is executed by a processor, it is used to implement the operation of the initial stress generation method for coal-bearing strata and tunnels in PFC3D as described in any one of claims 1-7.

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