Method for simulating disaster-causing effect of secondary disaster chain induced by rock burst

Abstract

The invention discloses a simulation method for a disaster-inducing effect of a secondary disaster chain induced by rock burst, and belongs to the field of coal mine disaster prevention and control. Establishing an FLAC three-dimensional numerical model to simulate supporting pressure distribution characteristics in a working face propulsion process, and dividing an advanced stress influence range; dividing an impact danger area according to the impact critical strength, and extracting advanced stress; the method comprises the following steps: collecting a coal body sample, performing a Hopkinson pressure bar test on the coal body sample, and testing the void ratio of the coal body sample by using a CT scanning technology; the method comprises the following steps: calculating gas flow under different impact strengths, establishing a Fluent three-dimensional numerical model according to geological conditions of mining engineering of a target mine, checking the model according to field measured data, simulating a spontaneous combustion three-zone distribution rule, and finally ascertaining the disaster-causing effect of a secondary disaster chain induced by rock burst. The method is simple in step, effectively finds the mutual influence relation of secondary disaster chains dominated and induced by rock burst, assists in cooperative prevention and control of disasters, and reduces the occurrence probability of multi-dynamic disasters.

Description

Technical Field

[0001] The invention belongs to the field of coal mine disaster prevention and control, and specifically relates to a method for simulating disaster-causing effects of secondary disaster chains induced by rock burst. Background Art

[0002] The current coal mining areas have four major characteristics: being the main battlefield for coal production, high production capacity, multiple disasters and difficult to manage. Their mining geological and hydrological conditions are complex, with complex conditions of "four highs and one hard", which lead to prominent problems of five major disasters: rock burst, water disasters, fire, gas and high temperature.

[0003] Rock burst is a common dynamic disaster in underground coal mining. It is often accompanied by sudden, rapid and violent eruption of coal and rock. The causes are very complex and there may not be any signs in advance. Under the influence of rock burst, the surrounding rock of the tunnel on site undergoes plastic deformation, the surrounding rock structure continues to evolve, the coal body is damaged and gas overflows, and there is air leakage in the goaf.

[0004] At present, many mechanisms have been formed in the prevention and control of rock burst, such as the "three-factor" theory and the dynamic and static load superposition induced rock burst theory. However, current research focuses on the impact of single rock burst disasters, and the research methods of the secondary disaster chain caused by rock burst have not yet appeared, and it is impossible to explore the connection between multiple disaster chains. Summary of the invention

[0005] Technical problem: The purpose of the present invention is to provide a method for simulating the disaster-causing effect of secondary disaster chains induced by rock burst, and to provide a means to explore the mechanism of the secondary disaster chain caused by rock burst. By establishing a FLAC three-dimensional numerical model to analyze the stress distribution characteristics, and then establishing a Fluent three-dimensional numerical model to analyze the evolution law of secondary disasters, the critical indicators of the occurrence of secondary disasters induced by rock burst are identified to achieve rock burst composite disaster prevention and control. The method has simple steps, is easy to use, and has good simulation effect.

[0006] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for simulating the disaster-causing effect of a secondary disaster chain induced by rock burst includes the following steps:

[0008] Step 1: According to the mining engineering geological conditions of the target mine, the FLAC three-dimensional numerical model of the working face area is established using the FLAC software to simulate the pressure distribution characteristics during the advancement of the working face. The simulation parameters of the FLAC three-dimensional numerical model are then updated based on the influence range of the lead stress measured on site and the pressure range of different advancement distances of the working face support;

[0009] Step 2: Collect gas-containing coal specimens of standard size from the working face of the target mine and combine them with the uniaxial compression test of the coal to obtain the critical impact strength of the coal, and obtain the impact risk danger area and maximum stress value corresponding to different advancement distances of the coal;

[0010] Step 3: According to the impact risk danger area and maximum stress value corresponding to different coal advancement distances, the Hopkinson pressure bar test is carried out on the gas-containing coal specimens, and the porosity of the gas-containing coal specimens under weak impact, medium impact and strong impact strength conditions is tested using CT scanning technology. The porosity of the gas-containing coal specimens is used to reflect the damage of the gas-containing coal specimens caused by impact;

[0011] Step 4: Using the porosity of the gas-containing coal specimen, calculate the gas flow rate under different impact damage degrees;

[0012] Step 5: According to the mining engineering geological conditions of the target mine, the FLUENT simulation software is used to establish a FLUENT 3D numerical model, and the modeling is adjusted according to the gas and oxygen concentration data obtained by the buried pipe in the goaf, so as to obtain the FLUENT 3D numerical model under the influence of gas concentration without impact, and reflect the distribution characteristics of the gas and spontaneous combustion symbiotic disaster area in the goaf from the FLUENT 3D numerical model;

[0013] Step 6: Import the impact risk danger zone corresponding to different advancement distances obtained by FLAC in step 2 and the gas flow data under different impact damage degrees obtained in step 4 into the gas source item of the coal body in the FLUENT simulation software, and obtain the change of gas concentration under critical impact, medium impact and strong impact conditions in the FLUENT three-dimensional numerical model, and simulate the distribution range of gas and spontaneous combustion co-existence zone in the goaf induced by impact ground pressure based on the change data of gas concentration and oxygen concentration data.

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

[0015] Furthermore, the FLAC three-dimensional numerical model of the working face area was established and adjusted by comparing it with the measured data:

[0016] The information on the pressure of the support on the working face is obtained based on the on-site actual measurement: the on-site hydraulic support uses its own stress monitoring device to record the stress distribution data of the hydraulic support at different advancement distances of the working face, so as to obtain the law of the pressure on the working face that changes with the advancement; the information on the influence range of the leading stress of the working face is obtained based on the on-site actual measurement: in the return air lane and transportation lane of the working face, anchor cable stress sensors are arranged at intervals at the leading working face, so as to obtain the data on the influence range of the leading stress with the advancement distance of the working face; the leading stress influence range, stress peak value and stress range are obtained by FLAC three-dimensional numerical model simulation, and the information on the influence range of the leading stress at different advancement distances measured on-site and the law of the pressure of the support on the working face are compared with the information obtained by FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, it can be considered that the simulation result of the FLAC three-dimensional numerical model is 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 result and the measured data is less than 10%.

[0017] Furthermore, the critical impact strength of the coal body that determines the occurrence of coal seam rock burst is empirically taken as 1.5 to 2 times the axial compressive strength of the gas-containing coal body specimen.

[0018] Furthermore, the impact strength T of the gas-containing coal specimen when it is completely crushed by the Hopkinson pressure bar impact is max As standard, weak impact strength is 10% T max , medium impact is 30% of T max , strong impact is 60% of T max， .

[0019] Furthermore, the following formula is used to calculate the gas flow rate under different impact damage degrees through the porosity of the gas-containing coal specimen:

[0020]

[0021] Where: Q represents gas flow; k 2 is the permeability coefficient of coal rock mass; φ is the porosity of coal rock mass; P 1 , P 2 The distribution represents 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 coal rock structure, pore characteristics and gas flow characteristics.

[0022] Furthermore, the steps of adjusting the modeling based on the gas and oxygen concentration data obtained by measuring the buried pipes in the goaf are as follows: based on the measured values ​​of the gas and oxygen concentrations in the goaf monitored by the on-site bundle pipes, determine whether the deviation between the distribution range of the gas and spontaneous combustion disaster area in the unimpacted 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 the actual situation; if so, update the model until the deviation between the simulation and the measured data is less than 10%.

[0023] Beneficial effects: The present invention proposes a simulation method for the disaster-causing effects of secondary disaster chain induced by rock burst, which mainly uses numerical simulation software combined with laboratory experiments and on-site measurement verification to provide a simulation method for the disaster-causing effects of secondary disaster chain induced by rock burst with intuitive effects, reliable results and strong operability. It is beneficial to explore the connection and influence mechanism of the secondary disaster chain induced by rock burst, and solves the problem that traditional disaster simulation only considers the influence relationship between a single disaster or two disasters, helps to block the incubation and evolution of secondary disasters, realizes the requirement of promoting the advanced governance of major disasters in coal mines, provides specific prevention and control opportunities, prevention and control locations, and prevention and control effect evaluation for the prevention and control of the secondary disaster chain induced by rock burst, and helps the coordinated prevention and control of secondary disasters induced by rock burst.

[0024] This method takes rock burst as the main factor and proposes a simulation method for the disaster-causing effect of the secondary disaster chain induced by rock burst. It has positive significance for blocking the incubation and evolution of secondary disasters, and is conducive to assisting coordinated disaster prevention and control and reducing the probability of multi-dynamic disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a method for simulating the disaster-causing effect of secondary disaster chain induced by rock burst in an embodiment of the present invention;

[0026] Figure 2 A FLAC three-dimensional numerical model diagram of a simulation method for the disaster-causing effect of a secondary disaster chain induced by rock burst in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the impact danger zone of the simulation method of the disaster-causing effect of the secondary disaster chain induced by rock burst in an embodiment of the present invention;

[0028] Figure 4 A Fluent three-dimensional numerical model diagram of a simulation method for the disaster-causing effect of a secondary disaster chain induced by rock burst in an embodiment of the present invention;

[0029] Figure 5 This is a simulation method for the disaster-causing effect of the secondary disaster chain induced by rock burst in an embodiment of the present invention, and a distribution map of the disaster area of ​​gas and spontaneous combustion co-existence in the goaf. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are further described below in conjunction with the accompanying drawings:

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

[0032] Step 1: According to the mining engineering geological conditions of the target mine, a FLAC three-dimensional numerical model is established, and the FLAC three-dimensional numerical model is adjusted according to the measured working face support pressure. The FLAC three-dimensional numerical model is used to simulate the support pressure distribution characteristics during the working face advancement process, and the advance stress influence range is divided; from the field measurement, the measured information of the advance stress influence range and the pressure range of the working face support at different advancement distances is obtained, and the measured information is compared with the simulated information. When the comparison deviation value does not exceed 10%, it is considered that the FLAC three-dimensional numerical model meets the requirements, otherwise the simulation parameters are updated to adjust the FLAC three-dimensional numerical model;

[0033] After the FLAC three-dimensional numerical model of the working face area is established, adjustments are made by comparing it with the measured data:

[0034] The information on the pressure of the support on the working face is obtained based on the on-site actual measurement: the on-site hydraulic support uses its own stress monitoring device to record the stress distribution data of the hydraulic support at different advancement distances of the working face, so as to obtain the law of the pressure on the working face that changes with the advancement; the information on the influence range of the leading stress of the working face is obtained based on the on-site actual measurement: in the return air lane and transportation lane of the working face, anchor cable stress sensors are arranged at intervals at the leading working face, so as to obtain the data on the influence range of the leading stress with the advancement distance of the working face; the leading stress influence range, stress peak value and stress range are obtained by FLAC three-dimensional numerical model simulation, and the information on the influence range of the leading stress at different advancement distances measured on-site and the law of the pressure of the support on the working face are compared with the information obtained by FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, it can be considered that the simulation result of the FLAC three-dimensional numerical model is 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 result and the measured data is less than 10%.

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

[0036] Step 2: Collect gas-containing coal specimens of standard size from the working face of the target mine and combine them with the uniaxial compression test of the coal to obtain the critical impact strength of the coal. Combined with the advance stress influence range obtained by simulating the FLAC three-dimensional numerical model that meets the requirements, the impact risk danger area and maximum stress value corresponding to different coal advancement distances are obtained;

[0037] The critical impact strength of coal mass for judging the occurrence of coal seam rock burst is empirically taken as 1.5 to 2 times of the axial compressive strength of gas-containing coal mass specimens.

[0038] Step 3: According to the impact risk danger area and maximum stress value corresponding to different coal advancement distances, the Hopkinson pressure bar test is carried out on the gas-containing coal specimens, and the porosity of the gas-containing coal specimens under weak impact, medium impact and strong impact strength conditions is tested using CT scanning technology. The porosity of the gas-containing coal specimens is used to reflect the damage of the gas-containing coal specimens caused by impact;

[0039] Impact strength T of gas-containing coal specimen completely broken by Hopkinson bar impact max As standard, weak impact strength is 10% T max , medium impact is 30% of T max , strong impact is 60% of T max， .

[0040] The compressive strength is used to determine whether rock burst occurs and the range of rock burst is given; the rock burst test is used to give the gas overflow concentration under different pressure conditions, which is used to predict the performance of the maximum situation;

[0041] Step 4: Using the porosity of the gas-containing coal specimen, calculate the gas flow rate under different impact damage degrees;

[0042] The following steps are used to calculate the gas flow rate under different impact damage degrees by using the porosity of the gas-containing coal specimen:

[0043]

[0044] Where: Q represents gas flow; k 2 is the permeability coefficient of coal rock mass; φ is the porosity of coal rock mass; P 1 , P 2 The distribution represents 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 coal rock structure, pore characteristics and gas flow characteristics.

[0045] Step 5: According to the mining engineering geological conditions of the target mine, the FLUENT simulation software is used to establish a FLUENT three-dimensional numerical model under the normal gas concentration without impact, and the modeling is adjusted according to the gas and oxygen concentration data obtained by the buried pipe in the goaf to obtain the FLUENT three-dimensional numerical model under the influence of gas concentration without impact. The distribution characteristics of the gas and spontaneous combustion symbiotic disaster area in the goaf are reflected from the FLUENT three-dimensional numerical model;

[0046] The steps for adjusting the modeling 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 the gas and oxygen concentrations in the goaf monitored by the on-site bundle pipes, determine whether the deviation between the distribution range of the gas and spontaneous combustion disaster area in the unimpacted goaf simulated by the FLUENT three-dimensional numerical model and the actual data is greater than 10%; if not, the model can be considered to be consistent with the actual situation; if so, update the model until the deviation between the simulation and the actual data is less than 10%.

[0047] Step 6: Import the impact risk danger area corresponding to different advancement distances obtained by FLAC in step 2 and the gas flow data under different impact damage degrees obtained in step 4 into the gas source item of the coal body in the FLUENT simulation software, and obtain the change of gas concentration under critical impact, medium impact and strong impact conditions in the FLUENT three-dimensional numerical model, and simulate the distribution range of gas and spontaneous combustion coexistence area in the goaf induced by rock burst according to the change data of gas concentration and oxygen concentration data. Parameters of critical impact, medium impact and strong impact conditions suffered from Hopkinson pressure bar impact.

[0048] Example: The established FLAC three-dimensional numerical model includes: the target mine working face length is 181m, the advancement length is 1090m, the coal thickness is 11m, the fully mechanized top coal caving mining technology is adopted, the long wall retreat mining method is used for mining, and the roof is managed by the full caving method; the overlying rock layer has 90-600m thick sandstone of the Luohe Formation, the coal seam has a strong impact tendency, and the roof and floor have a weak impact tendency; the microseismic data monitoring shows that the microseismic energy increases sharply at the 48th pressure (816m), reaching 8.78×104J, which is close to the warning value. The model verification is consistent with the actual situation, such as Figure 2 shown.

[0049] According to experience, the critical impact strength of coal is 1.5 to 2 times the uniaxial compressive strength of coal.

[0050] The critical indicators for determining the occurrence of rock burst in mines include the influence range of advance stress, the advancement distance of the working face, and the distance to the advance working face.

[0051] The rock burst danger zone obtained by simulation is within the range of 0 to 180 m of the leading working face. Figure 3 shown.

[0052] The gas flow rate is given by the formula Calculation, where: Q represents gas flow; k 2 is the permeability coefficient of coal rock mass; φ is the porosity of coal rock mass; P 1 , P 2 The distribution represents 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 coal rock structure, pore characteristics and gas flow characteristics.

[0053] A Fluent three-dimensional numerical model was established based on the gas flow rate, and the model verification was in line with the actual situation. Figure 4 As shown in the figure, the distribution characteristics of the three gas zones and the three spontaneous combustion zones are simulated to obtain the distribution of the gas and spontaneous combustion symbiosis zone, as shown in the figure. Figure 5 shown.

[0054] According to the simulation results of FLAC and Fluent, the evolution law of secondary disasters was obtained. The compound disaster was manifested as the incubation and evolution of the "rock burst-gas-fire" disaster chain.

[0055] The indicators for judging the occurrence of disasters in the target mine are obtained, including the range of the three spontaneous combustion zones, the overlapping range of 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 effect of secondary disaster chain induced by rock burst, characterized in that: The following steps are involved: Step 1: According to the mining engineering geological conditions of the target mine, the FLAC three-dimensional numerical model of the working face area is established using the FLAC software to simulate the pressure distribution characteristics during the advancement of the working face. The simulation parameters of the FLAC three-dimensional numerical model are then updated based on the influence range of the lead stress measured on site and the pressure range of different advancement distances of the working face support; Step 2: Collect gas-containing coal specimens of standard size from the working face of the target mine and combine them with the uniaxial compression test of the coal to obtain the critical impact strength of the coal, and obtain the impact risk danger area and maximum stress value corresponding to different advancement distances of the coal; Step 3: According to the impact risk danger area and maximum stress value corresponding to different coal advancement distances, the Hopkinson pressure bar test is carried out on the gas-containing coal specimens, and the porosity of the gas-containing coal specimens under weak impact, medium impact and strong impact strength conditions is tested using CT scanning technology. The porosity of the gas-containing coal specimens is used to reflect the damage of the gas-containing coal specimens caused by impact; Step 4: Using the porosity of the gas-containing coal specimen, calculate the gas flow rate under different impact damage degrees; Step 5: According to the mining engineering geological conditions of the target mine, the FLUENT simulation software is used to establish a FLUENT 3D numerical model, and the modeling is adjusted according to the gas and oxygen concentration data obtained by the buried pipe in the goaf, so as to obtain the FLUENT 3D numerical model under the influence of gas concentration without impact, and reflect the distribution characteristics of the gas and spontaneous combustion symbiotic disaster area in the goaf from the FLUENT 3D numerical model; Step 6: Import the impact risk danger zone corresponding to different advancement distances obtained by FLAC in step 2 and the gas flow data under different impact damage degrees obtained in step 4 into the gas source item of the coal body in the FLUENT simulation software, and obtain the change of gas concentration under critical impact, medium impact and strong impact conditions in the FLUENT three-dimensional numerical model, and simulate the distribution range of gas and spontaneous combustion co-existence zone in the goaf induced by impact ground pressure based on the change data of gas concentration and oxygen concentration data.

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

3. The method for simulating the disaster-causing effect of secondary disaster chain induced by rock burst according to claim 1 is characterized in that: After the FLAC three-dimensional numerical model of the working face area is established, adjustments are made by comparing it with the measured data: Obtain information on the pressure of the support on the working face based on on-site measurements: The on-site hydraulic support uses its own stress monitoring device to record the stress distribution data of the hydraulic support at different advancement distances of the working face, so as to obtain the pressure law of the working face as it changes with advancement; Obtain information on the influence range of the leading stress of the working face based on on-site measurements: In the transport lane of the return air lane of the working face, anchor cable stress sensors are arranged at intervals ahead of the working face, so as to obtain the influence range data of the leading stress as the working face advances; The influence range of advance stress, stress peak and stress range are obtained by simulating the FLAC three-dimensional numerical model. The influence range of advance stress at different advancing distances and the pressure law of the working face support measured on site are compared with the information obtained by FLAC three-dimensional numerical model simulation. If the numerical deviation is less than 10%, it can be considered that the simulation results of the FLAC three-dimensional numerical model are 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%.

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

5. The method for simulating the disaster-causing effect of secondary disaster chain induced by rock burst according to claim 1, characterized in that: Impact strength T of gas-containing coal specimen completely broken by Hopkinson bar impact max As standard, weak impact strength is 10%T max , medium impact is 30% of T max , strong impact is 60% of T max， .

6. The method for simulating the disaster-causing effect of secondary disaster chain induced by rock burst according to claim 1, characterized in that: The following steps are used to calculate the gas flow rate under different impact damage degrees by using the porosity of the gas-containing coal specimen: Where: Q represents gas flow rate; k2 is the permeability coefficient of coal rock mass; φ is the porosity of coal rock mass; P1 and P2 distribution 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 coal seam; n is an index parameter related to coal rock mass structure, pore characteristics and gas flow characteristics.

7. The method for simulating the disaster-causing effect of secondary disaster chain induced by rock burst according to claim 1, characterized in that: In step 5, the step of adjusting the modeling according to the gas and oxygen concentration data obtained by the actual measurement of the buried pipes in the goaf is: based on the measured values ​​of the gas and oxygen concentrations in the goaf monitored by the on-site bundle pipes, determine whether the deviation between the distribution range of the gas and spontaneous combustion disaster area in the unimpacted goaf simulated by the FLUENT three-dimensional numerical model and the measured data is greater than 10%; if not, it can be considered that the model is consistent with the actual situation; if so, update the model until the deviation between the simulation and the measured data is less than 10%.

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