Method for applying near field dynamic load of two-dimensional small model in numerical simulation

Abstract

The application relates to a method for applying near-field dynamic load of a two-dimensional small model in numerical simulation, which comprises the following steps: determining the size of a numerical model and establishing the numerical model by the geological environment near a studied roadway, simulating roadway excavation and calculating balance, collecting mine shock waveform signals recorded by a microseismic monitoring system, marking the P-wave first arrival time, solving the source position, determining the position of dynamic load design application according to the source distribution, grouping surface grids of a numerical model dynamic load application end according to the distance from the source, determining the time when the dynamic load propagates to each group and the time when the dynamic load of each group grid is applied according to the propagation speed of the dynamic load and the distance from the source to each group, and then applying the dynamic load to each group in time steps. The application makes the two-dimensional small model near-field dynamic load application conform to the characteristics that the vibration wave propagates from the center to the periphery, truly reflects the propagation characteristics of the vibration wave, obtains accurate simulation results, and meets the needs of underground safety production.

Description

Technical Field

[0001] This invention relates to a method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation, belonging to the field of coal mine safety mining and simulation technology. Background Technology

[0002] In recent years, with the rapid development of computer technology and numerical simulation technology, numerical simulation has become one of the important methods for modern engineering analysis and theoretical research. Numerical models can be divided into large models and small models according to their size. The computation time of a larger model will inevitably be longer than that of a smaller model. Therefore, small models can provide research results more quickly and intuitively to a certain extent.

[0003] Currently, the theoretical foundations for small-scale models do not yet meet the needs of production research, especially in simulating the propagation characteristics of seismic waves. Existing simulation methods for seismic waves in homogeneous rock media models simplify the dynamic load as a surface wave applied directly to the model surface when the seismic source is far from the roadway. However, when the seismic source is close to the roadway, this same simplification ignores the influence of spherical waves on the model, fails to reflect the characteristic of seismic waves propagating from the center outwards, and thus cannot accurately reflect the propagation characteristics of seismic waves, resulting in inaccurate simulation results and ultimately failing to provide a strong guarantee for safe underground mining. Therefore, the method for applying near-field dynamic loads to two-dimensional small-scale models is an important issue that urgently needs to be studied. Summary of the Invention

[0004] The purpose of this invention is to provide a method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation. This method enables the application of near-field dynamic loads to the two-dimensional small model to conform to the characteristics of vibration waves propagating from the center to the surroundings, thus realistically reflecting the propagation characteristics of vibration waves, obtaining accurate simulation results, and meeting the needs of safe production in downholes.

[0005] To achieve the above objectives, the present invention provides a method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation, comprising the following steps:

[0006] (1) Determine the size of the numerical model based on the geological environment near the tunnel under study and establish the numerical model;

[0007] (2) Simulate tunnel excavation and calculate the balance;

[0008] (3) Collect the seismic waveform signals recorded by the microseismic monitoring system, mark the arrival time of the P wave, and solve for the location of the seismic source; and determine the location where the dynamic load design is applied based on the distribution of the seismic source.

[0009] (4) Group the surface mesh of the dynamic load application end of the numerical model according to the distance from the earthquake source;

[0010] (5) Determine the time for the dynamic load to propagate to each group based on the propagation speed of the dynamic load and the distance from the source to each group, and then determine the time when the dynamic load is applied to each group of grids;

[0011] (6) Apply free field boundaries to the model, and apply dynamic loads to each group of grids according to the time of dynamic load application obtained in step (5).

[0012] Furthermore, the step of establishing the numerical model in step (1) is as follows:

[0013] a. Determine the size of the numerical model based on the geological environment near the roadway under study and establish the numerical model. Group the model according to the actual occurrence of coal and rock strata and set the model constitutive model as a Mohr-Coulomb model.

[0014] b. Based on the laboratory test results of the mechanical properties of coal and rock, assign the corresponding mechanical parameters of coal and rock strata to the model, including density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength;

[0015] c. Fix the bottom and sides of the model, and apply an equivalent load on top of the model to simulate the force of the overlying rock strata;

[0016] d. Set the gravitational acceleration to achieve initial equilibrium of ground stress.

[0017] Furthermore, the method for simulating tunnel excavation in step (2) is to set the constitutive model of the "tunnel" group to a null model or to directly delete the unit cells of the "tunnel" group.

[0018] Furthermore, the earthquake source in step (3) is represented as a point source in the numerical model.

[0019] Furthermore, in step (4), the numerical model surface mesh is grouped by dividing meshes whose center point is at the same distance from the earthquake source into the same group;

[0020] When the number of surface meshes n at the dynamic load application end of the numerical model is even, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is:

[0021] When the number of surface meshes n at the dynamic load application end of the numerical model is odd, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is:

[0022] In the formula, h k denoted as , where is the distance from the earthquake source to the k-th group of grids in the numerical model, and the group closest to the earthquake source on the surface of the numerical model is the first group; h is the closest distance from the earthquake source to the surface of the numerical model; m is the size of each grid on the surface of the numerical model.

[0023] Furthermore, when n is even, the number of mesh groups k on the dynamic load application end surface is... max The relationship between the number of grids n and the number of grids is as follows: When n is odd, the number of groups k max The relationship between the number of grids n and the number of grids is as follows:

[0024] Furthermore, the formula for calculating the time for dynamic load propagation to each group of grids in step (5) is as follows:

[0025] In the formula, t k is the time required for the dynamic load to propagate to the k-th grid; v is the propagation speed of the dynamic load.

[0026] Furthermore, the dynamic load applied in step (6) is in the form of a half-sine P-wave, as shown in the following formula:

[0027]

[0028] In the formula, f is the frequency of the dynamic load; the duration of the dynamic load is 1 / f.

[0029] Furthermore, the propagation speed of the dynamic load in step (5) is consistent with the propagation speed of the P-wave used by the microseismic monitoring system to solve for the location of the seismic source in step (2).

[0030] This invention determines the size of a numerical model based on the geological environment near the studied tunnel and establishes the numerical model. It simulates tunnel excavation and calculates equilibrium, collects seismic waveform signals recorded by a microseismic monitoring system, marks the arrival time of the P-wave, solves for the source location, and determines the location for dynamic load application based on the source distribution. The surface mesh of the dynamic load application end of the numerical model is grouped according to its distance from the source. The propagation speed of the dynamic load and the distance from the source to each group are used to determine the propagation time of the dynamic load to each group and the application time of the dynamic load to each group's mesh. Then, the dynamic load is applied to each group in a time-step manner. This invention ensures that the application of near-field external dynamic loads to the two-dimensional small model conforms to the characteristics of seismic waves propagating from the center outwards, realistically reflecting the propagation characteristics of seismic waves, obtaining accurate simulation results, and meeting the needs of safe underground production. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a surface mesh with an even number of meshes at the dynamic load application end of the numerical model of the present invention;

[0032] Figure 2 This is a schematic diagram of a surface mesh with an odd number of meshes at the dynamic load application end of the numerical model of the present invention;

[0033] Figure 3 This is a schematic diagram of the dynamic load application time in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the numerical model in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the mine seismic profile projection in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the grid grouping on the surface of the dynamic load application end in an embodiment of the present invention;

[0037] Figure 7 This is a diagram showing the effect of applying near-field dynamic load at a certain moment in an embodiment of the present invention. Detailed Implementation

[0038] The invention will now be further described with reference to the accompanying drawings.

[0039] (1) Determine the size of the numerical model based on the geological environment near the tunnel under study and establish the numerical model;

[0040] (2) Simulate tunnel excavation and calculate the balance;

[0041] (3) Collect the seismic waveform signals recorded by the microseismic monitoring system, mark the arrival time of the P wave, and solve for the location of the seismic source; and determine the location where the dynamic load design is applied based on the distribution of the seismic source.

[0042] (4) Group the surface mesh of the dynamic load application end of the numerical model according to the distance from the earthquake source;

[0043] (5) Determine the time for the dynamic load to propagate to each group based on the propagation speed of the dynamic load and the distance from the source to each group, and then determine the time when the dynamic load is applied to each group of grids;

[0044] (6) Apply free field boundaries to the model, and apply dynamic loads to each group of grids according to the time of dynamic load application obtained in step (5).

[0045] In a preferred embodiment, the step of establishing the numerical model in step (1) is as follows:

[0046] a. Determine the size of the numerical model based on the geological environment near the roadway under study and establish the numerical model. Group the model according to the actual occurrence of coal and rock strata and set the model constitutive model as a Mohr-Coulomb model.

[0047] b. Based on the laboratory test results of the mechanical properties of coal and rock, assign the corresponding mechanical parameters of coal and rock strata to the model, including density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength;

[0048] c. Fix the bottom and sides of the model, and apply an equivalent load on top of the model to simulate the force of the overlying rock strata;

[0049] d. Set the gravitational acceleration to achieve initial equilibrium of ground stress.

[0050] As a preferred embodiment, the method for simulating tunnel excavation in step (2) is to set the constitutive model of the "tunnel" group to a null model or to directly delete the unit cells of the "tunnel" group.

[0051] In a preferred embodiment, the seismic source in step (3) is represented as a point source in the numerical model.

[0052] In a preferred embodiment, in step (4), the numerical model surface mesh is grouped by dividing meshes whose center point is at the same distance from the earthquake source into the same group;

[0053] like Figure 1 As shown, when the number of surface meshes n at the dynamic load application end of the numerical model is even, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is:

[0054] like Figure 2 As shown, when the number of surface meshes n at the dynamic load application end of the numerical model is odd, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is:

[0055] In the formula, h k denoted as , where is the distance from the earthquake source to the k-th group of grids in the numerical model, and the group closest to the earthquake source on the surface of the numerical model is the first group; h is the closest distance from the earthquake source to the surface of the numerical model; m is the size of each grid on the surface of the numerical model.

[0056] Furthermore, when n is even, the number of mesh groups k on the dynamic load application end surface is... max The relationship between the number of grids n and the number of grids n is When n is odd, the number of groups k max The relationship between the number of grids n and the number of grids n is

[0057] In a preferred embodiment, the formula for calculating the time for dynamic load propagation to each group of grids in step (5) is as follows:

[0058] In the formula, t k is the time required for the dynamic load to propagate to the k-th grid; v is the propagation speed of the dynamic load.

[0059] As a preferred implementation method, such as Figure 3 As shown, the dynamic load applied in step (6) is a half-sine P-wave, and the formula is as follows:

[0060]

[0061] In the formula, f is the frequency of the dynamic load; the duration of the dynamic load is 1 / f.

[0062] To further improve the accuracy and realism of the simulation of external dynamic load application, the propagation speed of the dynamic load in step (5) is consistent with the propagation speed of the P-wave used by the microseismic monitoring system to solve for the source location in step (2).

[0063] Example:

[0064] The method was used to apply a two-dimensional small-model near-field dynamic load to the roadway on the 37221-1 working face of a certain mine. The specific steps are as follows:

[0065] (1) Based on the geological environment near the studied tunnel, the size of the numerical model was determined to be 50m × 50m (length × height), and a model was established as follows: Figure 4 The numerical model shown is based on the Mohr-Coulomb model; the physical and mechanical parameters of the coal and rock strata are listed in Table 1:

[0066] Table 1 Mechanical parameters of coal and rock strata

[0067]

[0068] (2) Assign null to the “tunnel” group, simulate tunnel excavation, and calculate the balance;

[0069] (3) Collect microseismic data with large energy during the mining of the 37221-1 working face, solve the location of the seismic source and analyze its distribution layer; Figure 5 This is a projection of the seismic profile of the mine, from Figure 5 It can be seen that the mine tremors are mainly distributed between 40m and 60m below the roadway on the 37221-1 working face. Therefore, the dynamic load is designed at 50m directly below the roadway, that is, 30m directly below the bottom of the model.

[0070] (4) Group the surface mesh of the numerical model according to its distance from the earthquake source. The grouping results are as follows: Figure 6 As shown, the side length m of the bottom mesh of the model is 2m. The mesh at the center of the bottom surface is the first group, and the mesh at the two side edges is the last group, for a total of 25 groups.

[0071] (5) Since the number of grids n = 50 at the dynamic load application end, i.e. the bottom of the model, is an even number, and the dynamic load is applied 30m directly below the bottom of the model, according to the formula... The distances from the first group to the second group are 30m, 30.04m, 30.10m, 30.20m, 30.34m, 30.50m, 30.70m, 30.92m, 31.18m, 31.47m, 31.78m, 32.13m, and 32.50m respectively. The distances from the fourteenth group are 32.90m, the fifteenth group is 33.32m, the sixteenth group is 33.77m, the seventeenth group is 34.24m, the eighteenth group is 34.73m, the nineteenth group is 35.25m, the twentieth group is 35.78m, the twenty-first group is 36.34m, the twenty-second group is 36.91m, the twenty-third group is 37.50m, the twenty-fourth group is 38.11m, and the twenty-fifth group is 38.73m.

[0072] (6) Set the propagation speed v of the dynamic load to 4100 m / s, and the application time of the first set of dynamic loads to 0, according to the formula Determine the time when dynamic load is applied to each group of meshes; therefore, the time when dynamic load is applied to the second group of meshes is 9.14e. -6 The dynamic load is applied to the third set of grids at time 2.54e. -5 The dynamic load is applied to the fourth grid group at time 4.96e. -5 The dynamic load was applied to the fifth grid group at 8.19e. -5 The dynamic load is applied to the sixth grid group at time 1.22e. -4 The dynamic load is applied to the seventh grid group at time 1.70e. -4 The dynamic load is applied to the eighth grid group at time 2.25e. -4 The dynamic load was applied to the ninth grid group at time 2.88e. -4 The dynamic load was applied to the tenth grid at time 3.58e. -4 The dynamic load is applied to the eleventh grid at time 4.35e. - 4 The dynamic load is applied to the twelfth grid group at time 5.19e. -4 The dynamic load was applied to the thirteenth grid at time 6.10e. -4 The dynamic load is applied to the fourteenth grid group at time 7.07e. -4 The dynamic load was applied to the fifteenth grid group at time 8.10e. -4The dynamic load was applied to the sixteenth grid group at 9.19e. -4 The dynamic load is applied to the seventeenth grid group at time 1.03e. -3 The dynamic load is applied to the eighteenth grid group at time 1.15e. -3 The dynamic load is applied to the nineteenth grid group at time 1.28e. -3 The dynamic load is applied to the twentieth grid at time 1.41e. -3 The dynamic load is applied to the twenty-first grid group at time 1.55e. -3 The dynamic load was applied to the twenty-second grid group at time 1.69e. -3 The dynamic load was applied to the twenty-third grid at time 1.83e. -3 The dynamic load was applied to the twenty-fourth grid at time 1.98e. -3 The dynamic load was applied to the twenty-fifth grid group at time 2.13e. -3 s;

[0073] (7) Apply free field boundaries to the model, and apply dynamic loads to each component time step according to the dynamic load application time obtained in step (6). The form of the dynamic load is a half-sine P-wave: Where f is set to 20Hz; the effect of the near-field dynamic load application process is as follows: Figure 7 As shown.

Claims

1. A method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation, characterized in that, Includes the following steps: (1) Determine the size of the numerical model based on the geological environment near the tunnel under study and establish the numerical model; (2) Simulate tunnel excavation and calculate the balance; (3) Collect the seismic waveform signals recorded by the microseismic monitoring system, mark the arrival time of the P wave, and solve for the location of the seismic source; and determine the location where the dynamic load design is applied based on the distribution of the seismic source; (4) Group the surface mesh of the dynamic load application end of the numerical model according to the distance from the seismic source; (5) Determine the time for the dynamic load to propagate to each group based on the propagation speed of the dynamic load and the distance from the source to each group, and then determine the time when the dynamic load is applied to each group of grids; (6) Apply free field boundaries to the model, and apply dynamic loads to each group of meshes according to the time of dynamic load application obtained in step (5); In step (4), the numerical model surface mesh is grouped by dividing meshes whose center point is at the same distance from the earthquake source into the same group; When the number of surface meshes n at the dynamic load application end of the numerical model is even, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is: ; When the number of surface meshes n at the dynamic load application end of the numerical model is odd, the formula for calculating the distance from the dynamic load to the surface mesh of the numerical model is: ; In the formula, h k denoted as , where is the distance from the earthquake source to the k-th group of grids in the numerical model, and the group of grids closest to the earthquake source on the surface of the numerical model is the first group. h is the closest distance from the earthquake source to the surface of the numerical model; m is the size of each grid on the surface of the numerical model; Furthermore, when n is even, the number of mesh groups k on the dynamic load application end surface is... max The relationship between the number of grids n and the number of grids is as follows: When n is odd, the number of groups k max The relationship between the number of grids n and the number of grids is as follows: ; The formula for calculating the time it takes for the dynamic load to propagate to each group of grids in step (5) is as follows: ; In the formula, t k is the time required for the dynamic load to propagate to the k-th grid; v is the propagation speed of the dynamic load.

2. The method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation according to claim 1, characterized in that, The steps for establishing the numerical model in step (1) are as follows: a. Determine the size of the numerical model based on the geological environment near the roadway under study and establish the numerical model. Group the model according to the actual occurrence of coal and rock strata and set the model constitutive model as a Mohr-Coulomb model. b. Based on the laboratory test results of the mechanical properties of coal and rock, assign the corresponding mechanical parameters of coal and rock strata to the model, including density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength; c. Fix the bottom and sides of the model, and apply an equivalent load on top of the model to simulate the force of the overlying rock strata; d. Set the gravitational acceleration to achieve initial equilibrium of ground stress.

3. The method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation according to claim 1, characterized in that, The method for simulating tunnel excavation in step (2) is to set the constitutive model of the "tunnel" group to a null model or to directly delete the unit cells of the "tunnel" group.

4. The method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation according to claim 1, characterized in that, The earthquake source in step (3) is represented as a point source in the numerical model.

5. The method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation according to claim 1, characterized in that, The dynamic load applied in step (6) is a half-sine P-wave, as shown in the following formula: ， In the formula, f is the frequency of the dynamic load; the duration of the dynamic load is 1 / f.

6. The method for applying near-field dynamic loads to a two-dimensional small model in numerical simulation according to claim 1, characterized in that, The propagation speed of the dynamic load in step (5) is the same as the propagation speed of the P-wave used by the microseismic monitoring system to solve for the location of the seismic source in step (2).

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