Multi-parameter Evolution Of Coal And Gas Outburst And Its Two-phase Flow Dynamic Response Under Gas-solid Coupling Effect

Coal and gas outburst,as a typical dynamic disaster in the production process of coal mines,severely restricts the current pace of safe,efficient and green development of"smart coal mines",and affects the implementation of China's"deep earth"and"deep blue"strategies in the coal industry.As there are many factors affecting coal and gas outburst,and the research of the coal mine dynamic disaster involves the intersection and integration of multiple disciplines such as rock mechanics,elastic-plastic mechanics,permeation fluid mechanics,fracture and damage mechanics,heat mass transfer,porous media theory,fluid mechanics and aerodynamics,and is limited by traditional research methods,making it difficult for scholars to explore the coal and gas outburst mechanism.To this end,this article starts with the two leading factors of coal and gas outburst,gas pressure and ground stress,based on a self-developed multi-field coupled coal mine disaster large-scale physical simulation test system,and adopts a systematic research method that combines indoor physical simulation,theoretical analysis and numerical simulation.Firstly,the multi-field state parameters,the dynamic evolution of energy storage and the dynamic behavior of coal-gas two-phase flow impact in the coal during the outburst under different gas pressure and geo-stress conditions were analyzed.Secondly,in order to gain a deeper understanding of the mechanism of gas pressure and geo-stress in the process of outburst,numerical simulations of the outburst process under the action of gas-solid coupling were carried out with the FVM-DEM coupling method and the two-fluid turbulence model.Through the above research,the following research progress has been made:(1)Based on the outburst key body structure,the concept of"coal-gas-surrounding rock-roadway"outburst system was proposed,and a set of multi-field coupling coal mine disaster large-scale physical simulation test system that can be used to carry out outburst physical simulation test research has been independently developed.The device can obtain real-time collection of multi-physical field state parameters in the coal body and roadway during the outburst process,providing a new method for the experimental research of coal and gas outburst and its disaster-causing mechanism.(2)Physical simulation tests of coal and gas outburst under different gas pressures and geo-stress conditions were carried out,the spatiotemporal evolution law of heat-fluid-solid state parameters in different areas,such as geo-stress,gas pressure and temperature were analyzed.On this basis,the release mechanism of elastic strain energy and gas expansion energy that evolve in real time in the thermal polytropic process and the influence of gas-solid coupling effect on the release of stress storage were discussed,and the differences of the failure mode of coal after outburst under different gas pressure and geo-stress conditions were compared.(3)Based on the multi-field coupling coal mine disaster large-scale physical simulation test system,the coal-gas two-phase flow behavior during the outburst process was reconstructed,the impact force signal of the coal-gas two-phase flow was obtained,and the impact force and the spatial evolution of temperature of coal-gas two-phase flow during outburst under different gas pressure and geo-stress conditions,as well as the sorting and deposition characteristics of outburst coal were discussed.Combining the theories of thermodynamics,aerodynamics,fluid mechanics,etc.,a physical model(PCEF model)of coal-gas flow with three key structures was proposed,the outburst coal-gas two-phase flow pattern and the formation mechanism of the complex wave system in the roadway during the process were deeply analyzed.(4)The FVM-DEM coupling numerical algorithm based on Open FOAM and PFC^3D was realized and the outburst process under different gas pressure and geo-stress conditions was reconstructed,and the real-time evolution of coal particle velocity,coal crack propagation,stress distribution characteristics and outburst intensity during outburst process was obtained,as well as the mechanism of gas and geo-stress in the process was further understood.Based on the two-fluid model and combined with the standard five-equation turbulence model,the coal-gas two-phase flow process under different gas pressure conditions was discussed,and the static pressure distribution,evolution of phase velocity and distribution characteristics of solid phase volume fraction in the roadway during the coal-gas two-phase flow process were obtained.Two numerical simulation methods provide new ideas for the study of coal and gas outburst.