A simulation method for the disaster-causing effect of rockburst-induced secondary disaster chain

Abstract

This invention discloses a simulation method for the disaster-causing effect of rockburst-induced secondary disaster chains, belonging to the field of coal mine disaster prevention and control. A FLAC three-dimensional numerical model is established to simulate the distribution characteristics of support pressure during the working face advancement process, and the influence range of advance stress is delineated. The impact hazard zone is divided according to the critical impact intensity, and the advance stress is extracted. Coal samples are collected, and Hopkinson bar tests are performed on the coal samples. CT scanning technology is used to test the porosity of the coal samples. Gas flow rate under different impact intensities is calculated. Based on the mining engineering geological conditions of the target mine, a Fluent three-dimensional numerical model is established. The model is verified based on field measured data to simulate the distribution law of the three spontaneous combustion zones, ultimately revealing the disaster-causing effect of rockburst-induced secondary disaster chains. This method has simple steps, effectively reveals the mutual influence relationship of rockburst-dominated secondary disaster chains, assists in the coordinated prevention and control of disasters, and reduces the probability of multi-dynamic disasters.

Description

Technical Field

[0001] This invention belongs to the field of coal mine disaster prevention and control, and specifically relates to a simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst. Background Technology

[0002] The current coal mining areas are characterized by four major features: coal production as the main battlefield, high production capacity, multiple disasters, and difficulty in management. Their mining geology and hydrology are complex, with complex conditions of "four highs and one hardness", which leads to prominent problems of five major disasters: rock bursts, water hazards, fires, gas, and high temperatures.

[0003] Rockburst is a common dynamic disaster in underground coal mining. Its manifestation is often accompanied by the sudden, rapid, and violent eruption of coal and rock masses. The causes are highly complex, and sometimes there are no prior warning signs. Affected by rockburst, the surrounding rock in the roadways undergoes plastic deformation, the rock structure continuously evolves, coal is damaged, gas leaks, and air leakage occurs in the goaf.

[0004] Currently, various mechanisms have been established for the prevention and control of rockbursts, such as the "three-factor" theory and the dynamic and static load superposition induced rockburst theory. However, current research focuses on the influence between individual rockburst disasters, and research methods for secondary disaster chains caused by rockbursts have not yet emerged, making it impossible to explore the connections between multiple disaster chains. Summary of the Invention

[0005] Technical Problem: The purpose of this invention is to provide a simulation method for the disaster-causing effect of rockburst-induced secondary disaster chains, and to provide a means to explore the occurrence mechanism of rockburst-induced secondary disaster chains. By establishing a FLAC three-dimensional numerical model to analyze stress distribution characteristics, and then establishing a Fluent three-dimensional numerical model to analyze the evolution law of secondary disasters, the critical indicators for the occurrence of rockburst-induced secondary disasters are determined, thereby achieving the prevention and control of rockburst-induced complex disasters. This method is simple in procedure, convenient to use, and has good simulation results.

[0006] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A simulation method for the disaster-causing effects of a secondary disaster chain induced by rock bursts includes the following steps:

[0008] Step 1: Based on the geological conditions of the target mine, use FLAC software to establish a FLAC three-dimensional numerical model of the working face area to simulate the pressure distribution characteristics during the working face advance. Then, combine the measured range of the influence of the advanced stress on the field and the range of pressure due to different advance distances of the working face support to verify and update the simulation parameters of the FLAC three-dimensional numerical model.

[0009] Step 2: Collect standard-sized gas-bearing coal samples from the working face of the target mine and combine them with uniaxial compression tests to obtain the critical impact strength of the coal, and obtain the impact risk hazard area and maximum stress value corresponding to different coal advance distances;

[0010] Step 3: Based on the impact risk hazard area and maximum stress value corresponding to different advance distances of the coal body, Hopkinson bar tests were conducted on the gas-bearing coal body specimens. CT scanning technology was used to test the porosity of the gas-bearing coal body specimens under weak, medium, and strong impact intensities, respectively. The porosity of the gas-bearing coal body specimens was used to reflect the impact-induced damage to the gas-bearing coal body specimens.

[0011] Step 4: Calculate the gas flow rate under different impact damage levels using the porosity of the gas-bearing coal sample;

[0012] Step 5: Based on the geological conditions of the target mine, use FLUENT simulation software to establish a FLUENT three-dimensional numerical model, and adjust the model according to the gas and oxygen concentration data obtained from the actual measurement of the buried pipe in the goaf, to obtain a FLUENT three-dimensional numerical model under the influence of gas concentration in the absence of impact, and reflect the distribution characteristics of the gas and spontaneous combustion symbiotic disaster area in the goaf from the FLUENT three-dimensional numerical model.

[0013] Step 6: Import the impact risk hazard areas corresponding to different advance distances obtained from FLAC in Step 2 and the gas flow data under different impact damage levels obtained in Step 4 into the gas source term of the coal body in the FLUENT simulation software to obtain the changes in gas concentration in the FLUENT three-dimensional numerical model under critical impact, moderate impact and strong impact conditions, and simulate the distribution range of gas and spontaneous combustion coexistence zone in the goaf induced by rockburst based on the gas concentration change data and oxygen concentration data.

[0014] Furthermore, the mining engineering geological conditions of the target mine include the working face mining size, goaf void distribution, caving zone fracture zone height, oxygen consumption rate, ventilation pressure, working face advance speed, burial depth, coal, lithology and thickness of the working face roof and floor, density, bulk modulus, shear modulus, tensile strength, cohesion, and internal friction angle.

[0015] Furthermore, after establishing a FLAC three-dimensional numerical model of the working area, adjustments were made by comparing it with measured data.

[0016] Information on the pressure on the working face supports was obtained based on on-site measurements: the hydraulic supports used their built-in stress monitoring devices to record the stress distribution data of the hydraulic supports at different advance distances of the working face, thereby obtaining the working face pressure law that changes with the advance distance; information on the influence range of the working face's advance stress was also obtained based on on-site measurements: in the return airway and transport roadway of the working face, anchor cable stress sensors were arranged at intervals ahead of the working face, thereby obtaining data on the influence range of the advance stress that changes with the working face advance distance; the influence range, peak stress, and stress range of the advance stress were obtained through FLAC three-dimensional numerical model simulation. The information on the influence range of the advance stress at different advance distances and the working face support pressure law obtained from the on-site measurements were compared with the information obtained from the FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, the simulation results of the FLAC three-dimensional numerical model can be considered to be consistent with the actual situation. If it is greater than 10%, the parameters of the FLAC three-dimensional numerical model are updated until the deviation between the simulation results and the measured data is less than 10%.

[0017] Furthermore, the critical strength of the coal body for determining the occurrence of coal seam rockburst is empirically taken as 1.5 to 2 times the axial compressive strength of the gas-bearing coal body specimen.

[0018] Furthermore, the impact strength T when the Hopkinson bar impact causes the gas-bearing coal sample to completely break is determined. max As a standard, the weak impact strength is 10% T. max A moderate impact of 30% T max The strong impact is 60% T max .

[0019] Furthermore, the following steps are taken to calculate the gas flow rate under different impact damage levels using the porosity of the gas-bearing coal sample:

[0020]

[0021] In the formula: Q represents gas flow rate; k2 is the permeability coefficient of coal and rock mass; φ is the porosity of coal and rock mass; P1 and P2 distributions represent the pressure before and after gas flow; μ is the dynamic viscosity of gas; L is the distance or path length of gas flow in the coal seam; n is an exponential parameter related to the structure, porosity characteristics and gas flow characteristics of coal and rock mass.

[0022] Furthermore, the steps for adjusting the model based on the gas and oxygen concentration data obtained from the actual measurement of buried pipes in the goaf are as follows: Based on the actual measured values ​​of gas and oxygen concentration in the goaf monitored by the on-site bundled pipes, determine whether the deviation between the distribution range of gas and spontaneous combustion symbiotic disaster area in the non-impact goaf simulated by the FLUENT three-dimensional numerical model and the measured data is greater than 10%. If not, the model can be considered to be consistent with reality; if so, update the model until the deviation between the simulation and the measured data is less than 10%.

[0023] Beneficial Effects: This invention proposes a simulation method for the disaster-causing effects of rockburst-induced secondary disaster chains. Using numerical simulation software as the primary method, combined with laboratory experiments and field measurements for verification, it provides a simulation method for the disaster-causing effects of rockburst-induced secondary disaster chains that is intuitive, reliable, and highly operable. This method is beneficial for elucidating the connections and influence mechanisms of rockburst-induced secondary disaster chains, addressing the limitations of traditional disaster simulations that only consider the influence relationship between a single rockburst or two disasters. It helps to prevent the gestation and evolution of secondary disasters, fulfilling the requirement for advanced management of major coal mine disasters. Furthermore, it provides specific timing, location, and effectiveness assessment for the prevention and control of rockburst-induced secondary disaster chains, contributing to the coordinated prevention and control of rockburst-induced secondary disasters.

[0024] This method, with rockburst as the dominant factor, proposes a simulation method for the disaster-causing effect of rockburst-induced secondary disaster chains. This method is of positive significance for blocking the gestation and evolution of secondary disasters, and is conducive to assisting in the coordinated prevention and control of disasters and reducing the probability of multi-dynamic disasters. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst in an embodiment of the present invention.

[0026] Figure 2 The image shows a FLAC three-dimensional numerical model of the simulation method for the disaster-causing effect of rockburst-induced secondary disaster chain in this embodiment of the invention.

[0027] Figure 3 This is a schematic diagram of the impact hazard zone for the simulation method of the disaster-causing effect of the secondary disaster chain induced by rockburst in an embodiment of the present invention;

[0028] Figure 4 The Fluent three-dimensional numerical model diagram is shown for the simulation method of the disaster-causing effect of rockburst-induced secondary disaster chain in this embodiment of the invention.

[0029] Figure 5 This is a distribution map of the goaf gas and spontaneous combustion symbiotic disaster zone in the simulation method of the secondary disaster chain induced by rockburst in this embodiment of the invention. Detailed Implementation

[0030] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0031] like Figure 1 As shown, this invention discloses a method for simulating the disaster-causing effects of a secondary disaster chain induced by rockburst, comprising the following steps:

[0032] Step 1: Based on the geological conditions of the target mine, establish a FLAC three-dimensional numerical model. Adjust the FLAC three-dimensional numerical model according to the measured working face support pressure. Use the FLAC three-dimensional numerical model to simulate the support pressure distribution characteristics during the working face advancement process and delineate the range of influence of the advance stress. Obtain the measured information of the range of influence of the advance stress and the range of pressure at different advancement distances of the working face support from the field. Compare the measured information with the simulated information. If the deviation value of the comparison does not exceed 10%, the FLAC three-dimensional numerical model is considered to meet the requirements. Otherwise, update the simulation parameters and adjust the FLAC three-dimensional numerical model.

[0033] After establishing the FLAC three-dimensional numerical model of the working surface area, adjustments are made by comparing it with measured data.

[0034] Information on the pressure on the working face supports was obtained based on on-site measurements: the hydraulic supports used their built-in stress monitoring devices to record the stress distribution data of the hydraulic supports at different advance distances of the working face, thereby obtaining the working face pressure law that changes with the advance distance; information on the influence range of the working face's advance stress was also obtained based on on-site measurements: in the return airway and transport roadway of the working face, anchor cable stress sensors were arranged at intervals ahead of the working face, thereby obtaining data on the influence range of the advance stress that changes with the working face advance distance; the influence range, peak stress, and stress range of the advance stress were obtained through FLAC three-dimensional numerical model simulation. The information on the influence range of the advance stress at different advance distances and the working face support pressure law obtained from the on-site measurements were compared with the information obtained from the FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, the simulation results of the FLAC three-dimensional numerical model can be considered to be consistent with the actual situation. If it is greater than 10%, the parameters of the FLAC three-dimensional numerical model are updated until the deviation between the simulation results and the measured data is less than 10%.

[0035] The geological conditions of the target mine include the working face size, the distribution of voids in the goaf, the height of the caving zone and fracture zone, the oxygen consumption rate, the ventilation pressure, the working face advance speed, the burial depth, the coal, the lithology and thickness of the working face roof and floor, the density, the bulk modulus, the shear modulus, the tensile strength, the cohesion, and the internal friction angle.

[0036] Step 2: Collect standard-sized gas-bearing coal samples from the working face of the target mine and combine them with uniaxial compression tests to obtain the critical impact strength of the coal. Combine this with the advanced stress influence range obtained by FLAC three-dimensional numerical model simulation that meets the requirements to obtain the impact risk danger area and maximum stress value corresponding to different coal advance distances.

[0037] The critical strength of the coal body for determining the occurrence of coal seam rockburst is empirically taken as 1.5 to 2 times the axial compressive strength of the gas-bearing coal body specimen.

[0038] Step 3: Based on the impact risk hazard area and maximum stress value corresponding to different advance distances of the coal body, Hopkinson bar tests were conducted on the gas-bearing coal body specimens. CT scanning technology was used to test the porosity of the gas-bearing coal body specimens under weak, medium, and strong impact intensities, respectively. The porosity of the gas-bearing coal body specimens was used to reflect the impact-induced damage to the gas-bearing coal body specimens.

[0039] The impact strength T of a gas-bearing coal specimen when subjected to Hopkinson bar impact causes complete fragmentation. max As a standard, the weak impact strength is 10% T. max A moderate impact of 30% T max The strong impact is 60% T max .

[0040] The compressive strength is used to determine whether a rockburst has occurred and to indicate the range of its occurrence; the impact test provides the gas overflow concentration under different pressure conditions, which is used to predict the maximum occurrence.

[0041] Step 4: Calculate the gas flow rate under different impact damage levels using the porosity of the gas-bearing coal sample;

[0042] The steps for calculating the gas flow rate under different impact damage levels using the porosity of gas-bearing coal samples are as follows:

[0043]

[0044] In the formula: Q represents gas flow rate; k2 is the permeability coefficient of coal and rock mass; φ is the porosity of coal and rock mass; P1 and P2 distributions represent the pressure before and after gas flow; μ is the dynamic viscosity of gas; L is the distance or path length of gas flow in the coal seam; n is an exponential parameter related to the structure, porosity characteristics and gas flow characteristics of coal and rock mass.

[0045] Step 5: Based on the geological conditions of the target mine, use FLUENT simulation software to establish a three-dimensional numerical model of FLUENT under normal conditions without the influence of impact gas concentration. Adjust the model according to the gas and oxygen concentration data obtained from the actual measurement of buried pipes in the goaf, and obtain a three-dimensional numerical model of FLUENT under the influence of gas concentration without impact. The distribution characteristics of the goaf gas and spontaneous combustion symbiotic disaster area are reflected from the three-dimensional numerical model of FLUENT.

[0046] The steps for adjusting the model based on the gas and oxygen concentration data obtained from the actual measurement of buried pipes in the goaf are as follows: Based on the actual measured values ​​of gas and oxygen concentration in the goaf monitored by the on-site bundled pipes, determine whether the deviation between the distribution range of gas and spontaneous combustion symbiotic disaster area in the non-impact goaf simulated by the FLUENT three-dimensional numerical model and the measured data is greater than 10%. If not, the model can be considered to be consistent with reality; if so, update the model until the deviation between the simulation and the measured data is less than 10%.

[0047] Step 6: Import the impact risk hazard areas corresponding to different advance distances obtained from FLAC in Step 2, and the gas flow data under different impact damage levels obtained in Step 4, into the gas source term of the coal seam in the FLUENT simulation software. Obtain the gas concentration changes in the FLUENT three-dimensional numerical model under critical, moderate, and strong impact conditions. Based on the gas concentration change data and oxygen concentration data, simulate the distribution range of the gas and spontaneous combustion coexistence zone in the goaf induced by rockburst. Parameters for Hopkinson bar impact under critical, moderate, and strong impact conditions are also included.

[0048] Example: The established FLAC three-dimensional numerical model includes: a target mine working face length of 181m, an advance length of 1090m, a coal thickness of 11m, employing fully mechanized top-coal caving mining technology, longwall retreat mining, and total caving roof management; the overlying strata contain a 90-600m thick Luohe Formation sandstone, the coal seam has a strong tendency to impact, and the roof and floor have a weak tendency to impact; microseismic data monitoring shows that at the 48th pressure event (816m), the microseismic energy increased sharply, reaching 8.78×10⁴J, close to the warning value, and the model verification is consistent with reality. Figure 2 As shown.

[0049] The critical impact strength of coal is empirically taken as 1.5 to 2 times the uniaxial compressive strength of coal.

[0050] Critical indicators for determining the occurrence of rockburst in mines include the range of influence of pre-stress, the working face advance distance, and the distance of the working face ahead.

[0051] The simulated rockburst hazard zone is within 0–180m of the working face, such as… Figure 3 As shown.

[0052] Gas flow rate is given by the formula The calculation is as follows: Q represents the gas flow rate; k2 is the permeability coefficient of the coal and rock mass; φ is the porosity of the coal and rock mass; P1 and P2 represent the pressure before and after gas flow; μ is the dynamic viscosity of the gas; L is the distance or path length of the gas flow in the coal seam; and n is an exponential parameter related to the structure, porosity characteristics and gas flow characteristics of the coal and rock mass.

[0053] A Fluent three-dimensional numerical model was established based on the gas flow rate. The model verification showed that it conformed to reality. Figure 4 As shown, the distribution characteristics of the three gas zones and three spontaneous combustion zones are simulated, and the distribution of the gas and spontaneous combustion coexistence zone is obtained, as follows. Figure 5 As shown.

[0054] Based on the simulation results of FLAC and Fluent, the evolution law of secondary disasters was obtained. The complex disaster form is manifested as the gestation and evolution of the disaster chain of "rockburst-gas-fire".

[0055] The indicators for determining the occurrence of disasters in target mines include the range of the three spontaneous combustion zones, the overlap between the spontaneous combustion zone and the gas explosion zone, and the distance to the lagging working face.

Claims

1. A method for simulating the disaster-causing effects of a secondary disaster chain induced by rockburst, characterized in that: Includes the following steps: Step 1: Based on the geological conditions of the target mine, use FLAC software to establish a FLAC three-dimensional numerical model of the working face area to simulate the pressure distribution characteristics during the working face advance. Then, combine the measured range of the influence of the advanced stress on the field and the range of pressure due to different advance distances of the working face support to verify and update the simulation parameters of the FLAC three-dimensional numerical model. Step 2: Collect standard-sized gas-bearing coal samples from the working face of the target mine and combine them with uniaxial compression tests to obtain the critical impact strength of the coal, and obtain the impact risk hazard area and maximum stress value corresponding to different coal advance distances; Step 3: Based on the impact risk hazard area and maximum stress value corresponding to different advance distances of the coal body, Hopkinson bar tests were conducted on the gas-bearing coal body specimens. CT scanning technology was used to test the porosity of the gas-bearing coal body specimens under weak, medium, and strong impact intensities, respectively. The porosity of the gas-bearing coal body specimens was used to reflect the impact-induced damage to the gas-bearing coal body specimens. Step 4: Calculate the gas flow rate under different impact damage levels using the porosity of the gas-bearing coal sample; Step 5: Based on the geological conditions of the target mine, use FLUENT simulation software to establish a FLUENT three-dimensional numerical model, and adjust the model according to the gas and oxygen concentration data obtained from the actual measurement of the buried pipe in the goaf, to obtain a FLUENT three-dimensional numerical model under the influence of gas concentration in the absence of impact, and reflect the distribution characteristics of the gas and spontaneous combustion symbiotic disaster area in the goaf from the FLUENT three-dimensional numerical model. Step 6: Import the impact risk hazard areas corresponding to different advance distances obtained from FLAC in Step 2 and the gas flow data under different impact damage levels obtained in Step 4 into the gas source term of the coal body in the FLUENT simulation software to obtain the changes in gas concentration in the FLUENT three-dimensional numerical model under critical impact, moderate impact and strong impact conditions, and simulate the distribution range of gas and spontaneous combustion coexistence zone in the goaf induced by rockburst based on the gas concentration change data and oxygen concentration data.

2. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that: The geological conditions of the target mine include the working face size, the distribution of voids in the goaf, the height of the caving zone and fracture zone, the oxygen consumption rate, the ventilation pressure, the working face advance speed, the burial depth, the coal, the lithology and thickness of the working face roof and floor, the density, the bulk modulus, the shear modulus, the tensile strength, the cohesion, and the internal friction angle.

3. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that, After establishing the FLAC three-dimensional numerical model of the working surface area, adjustments are made by comparing it with measured data. Information on the pressure on the working face support was obtained based on on-site measurements: The hydraulic support on-site used its built-in stress monitoring device to record the stress distribution data of the hydraulic support at different advance distances of the working face, thereby obtaining the working face pressure pattern as the face advances; Information on the influence range of the working face's advance stress was obtained based on on-site measurements: Anchor bolt stress sensors were arranged at intervals in the transport roadway of the working face's return airway, thereby obtaining data on the influence range of the advance stress as the working face advances. The influence range, peak stress, and stress range of the advanced stress were obtained by FLAC three-dimensional numerical model simulation. The influence range of the advanced stress at different advance distances and the pressure law of the working face support were compared with the information obtained by FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, the simulation results of FLAC three-dimensional numerical model can be considered to be consistent with the actual situation. If it is greater than 10%, the parameters of FLAC three-dimensional numerical model are updated until the deviation between the simulation results and the measured data is less than 10%.

4. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that: In step 2, the critical strength of the coal body for determining the occurrence of coal seam rockburst is empirically taken as 1.5 to 2 times the axial compressive strength of the gas-bearing coal body specimen.

5. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that: The impact strength T of a gas-bearing coal specimen when subjected to Hopkinson bar impact causes complete fragmentation max As a standard, the weak impact strength is 10%T. max A moderate impact of 30% T max The strong impact is 60% T max .

6. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that: The steps for calculating the gas flow rate under different impact damage levels using the porosity of gas-bearing coal samples are as follows: In the formula: Q represents gas flow rate; k2 is the permeability coefficient of coal and rock mass; φ is the porosity of coal and rock mass; P1 and P2 distributions represent the pressure before and after gas flow; μ is the dynamic viscosity of gas; L is the distance or path length of gas flow in the coal seam; n is an exponential parameter related to the structure, porosity characteristics and gas flow characteristics of coal and rock mass.

7. The simulation method for the disaster-causing effect of a secondary disaster chain induced by rockburst according to claim 1, characterized in that: In step 5, the step of adjusting the model based on the gas and oxygen concentration data obtained from the actual measurement of the buried pipe in the goaf is as follows: Based on the actual measured values ​​of gas and oxygen concentration in the goaf monitored by the on-site bundled pipe, determine whether the deviation between the distribution range of gas and spontaneous combustion symbiotic disaster area in the non-impact goaf simulated by the FLUENT three-dimensional numerical model and the measured data is greater than 10%. If not, the model can be considered to be consistent with reality; if so, update the model until the deviation between the simulation and the measured data is less than 10%.

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