Research On The Flow Characteristics And Gas Permeability Of Soft Coal After Stress Peak

With the development of science and technology,the application of gas drainage technology in the mining area,seepage characteristics in China Coal evolution has made some achievements,to a certain extent,better guidance in the process of coal mining gas drainage and anti-reflection technology.At present,there are few researches on the evolution characteristics of permeability and the law of gas flow for the peak strength of coal.Based on this,this paper combines the theoretical analysis,laboratory experiments,numerical simulation and other means to carry out the study on the permeability and gas flow law of the peak strength of coal.The main achievements are as follows:(1)The permeability evolution model of the whole stress-strain and unloading process of the coal body is established,and the basic function relation between the permeability and the stress is obtained and visualized by the image;(2)In the laboratory,the evolution of permeability of the standard coal sample under different confining pressure(2MPa,3MPa,4MPa)is compared.The results show that under confining pressure of 2MPa,3MPa,4MPa,the permeability of the unloaded axial pressure and confining pressure increased about 1.3 times,and the evolution curve of permeability during the unloading process and the given confining pressure loading to secondary failure was plotted and the stress was simulated.The basic law of permeability variation with stress is obtained;(3)The RFPA software was used to simulate the crack propagation process and corresponding AE energy of coal samples under different confining pressures.The results showed that the development of fracture was divided into four stages: micro-damage nucleation,growth stage,micro-damage growth,And the formation of large-scale fracture stage,the rapid expansion of macro-fracture,the connection stage,large fracture through stage.And the process of X and Y displacement vectors of coal sample in the process is deeply analyzed to better understand the whole process of crack propagation;(4)The comsol software was used to simulate the distribution of the gaspressure and flow field in the coal body when the cracks were located in different positions of the coal body and the number of cracks in the coal body was different.It was shown that the existence of the fracture changed the original gas flow The gas flow along the fracture channel,part of the gas from the crevice entrance into the fracture channel,the other part from the coal matrix perpendicular to the fracture surface into the crack channel,the flow velocity at the crack inlet and outlet is far greater than other locations,cracks in a large extent On the increase of coal permeability;The research content of this paper provides a theoretical basis for gas drainage and gas management.Based on the exploration of the evolution of post-peak strength and permeability,combined with other gas control measures,the comprehensive gas control can better solve the gas Overrun and local gas accumulation problems.