A Fluid-Structure Interaction Simulation of Coal and Gas Outbursts Based on the Interaction between the Gas Pressure and Deformation of a Coal-Rock Mass

Abstract

Based on the theories of the gas seepage in coal seams and the deformation of the coal-rock medium, the gas seepage field in coal-rock mass is coupled with the deformation field of the coal-rock mass to establish a fluidstructure interaction model for the interaction between coal gas and coal-rock masses. The outburst process in coal-rock masses under the joint action of gas pressure and crustal stress is simulated using the material point method. The simulation results show the changes in gas pressure, velocity distribution, maximum principal stress distribution, and damage distribution during the process of the coal and gas outburst, as well as the movement and accumulation of coal-rock masses after the occurrence of the outburst. It was found that the gas pressure gradient was greatest at the working face after the occurrence of the outburst, the gas pressures and pressure gradients at each location within the coal seam gradually decreased with time, and the damage distribution was essentially the same as the minimum principal stress distribution. The simulation further revealed that the outburst first occurred in the middle of the tunnel excavation face and that the speed at which particles of coal mass were ejected was highest at the center and decreased toward the upper and lower sides. The study provides a scientific basis for enhancing our understanding of the mechanism behind coal and gas outbursts, as well as their prevention and control.

Anisotropic Flow-Solid Coupling Model for Gas Extraction from Cis-Layer Boreholes and Its Application

“…On the basis of the established recovery flow-solid coupling model, relevant experts and scholars have conducted research on borehole gas extraction. In terms of numerical simulation, the influence of ground stress factors on permeability is very significant, and a multistage pore fluid–solid coupling model considering the influence of ground stress factors on gas seepage is established; , flow-solid coupling mathematical models of coal and gas protrusion considering moisture, stress damage, and permeability coefficient factors are established; − flow-solid coupling models of multiphysical field coupling considering different physical field factors are established; , experimental study of coal permeability was carried out under consideration of effective stress, matrix expansion/contraction, and gas slip factors, , and then, matrix expansion/contraction factors were provided to the coal seam gas transport flow-solid coupling model. , In terms of gas extraction from boreholes, the extraction radius of underground gas extraction boreholes is deduced by numerical simulation method and verified on site; , gas migration characteristics of coal seam considering high-stress factors are studied, and the mechanism of gas extraction efficiency improved by pressure relief mining technology is further elaborated; considering the influence of the number of boreholes on gas extraction, the pressure sensor was used to monitor the change of gas pressure under a different number of boreholes; the theoretical equation of the plastic zone radius considering the plastic deformation factor was established, and the effective radius of gas extraction in the plastic zone was determined; considering the factor of water content, different water content factors are provided to study the change of gas pressure in coal seam gas extraction . In terms of laboratory experimental research, different physical and chemical factors of the coal body are considered to carry out experimental studies on the seepage characteristics of different coal steps, and the gas transport characteristics of the coal body under different fracture scales are studied. − Based on the self-developed coal triaxial seepage instrument and low-field NMR instrument, the adsorption characteristics and pore size distribution characteristics of different coal ranks were studied, and the seepage characteristics of different bedding coal bodies were obtained. − From microscopic and macroscopic perspectives, it can reveal the coal pore size distribution and gas transport characteristics comprehensively from microscopic and macroscopic perspectives, which is of guiding significance for coal seam gas extraction.…”