Criteria For Flow Regime Transition Of Gas For Pressure-relief In Mining-induced Fissure Under Multiple Factors

After the coal seam is mined,the overlying rock forms a "three-zone" division,in which the fault zone supports the adjacent layer and connects with the mined-out area,which is the only place for gas from the adjacent layer to influx into the working face,and it is also the gas floating and accumulating in the mined-out area.Important place.The mining cracks in the fault zone are fully developed,which provides good operating conditions for the gas drainage project.This project is based on the analysis of the morphological response and evolution law of the mining fractures in the fracture zone during the stress recovery process,taking the gas flow field in the fracture zone as the research object,paying attention to the pressure relief gas flow characteristics in the mining fractures,using theoretical analysis,laboratory Experiments and numerical simulation methods are used to study and analyze the effects of different fracture openings under a single fracture in the discrete fracture network model and the effects of different fracture surface conditions on the gas flow field,and determine the criteria for the transition of pressure relief gas flow under the influence of multiple factors,and obtain The following results:(1)Based on the analysis of the response and evolution of mining fractures,as well as the combing of the basic theories of pressure relief gas flow in mining fractures,three types of equivalent fracture surface structure models for single fractures are proposed—smooth parallel plate fracture model,trapezoid Platform meshing crack model and interstitial filling crack model;(2)Based on the smooth parallel plate fracture model,build an experimental platform for simulating four groups of artificial fractures with different fracture openings,control the flow of air fluid into the channels of the fractures to carry out flow experiments,and study and analyze the flow rate and pressure difference,as well as the flow rate and pressure difference.The flow pattern index method is used to obtain four sets of artificial fissure air flow state transition criteria under different fissure openings;(3)Based on the trapezoidal platform meshing crack model and the interstitial filling crack model,six groups of different crack models are proposed,and numerical calculations are carried out using ANSYS simulation to obtain the flow field change laws under different models and simulation schemes.This study is based on the discrete fracture network model framework,with the flow field of mining fractures as the core,through experiments and simulations obtained by the multifactor influence of the pressure relief gas flow in a single fracture to determine the flow regime,to obtain the fracture network in the fracture zone The spatial distribution characteristics and time evolution of pressure relief gas flow patterns are of great significance.