Microscopic investigation of the effect of uniaxial stress on the structure of pore-fissure system and methane adsorption in lean coal

In order to study the mechanism of interaction between stress, pore-fissure system, and methane adsorption. Adopting a novel combination of experimental and simulation methods. Through uniaxial fracture experiments and X-ray micro-CT scanning experiments, it was found that the pore-fissure system of coal blocks first closed and then sharply increased with the increase of uniaxial stress. Based on relevant experiments, unit cell models under different uniaxial stresses were constructed. Through simulation calculations using Zeo++-0.3 code and Materials Studio, it was found that the pore system of unit cells first decreases and then increases with the increase of uniaxial stress, and the maximum adsorption capacity of methane first decreases and then increases. The experimental and simulation results for the evolution characteristics of the coal pore system under different uniaxial stresses were consistent. Stress affects methane adsorption in coal by altering the pore-fissure system characteristics. Stress has a significant impact on the macroscopic and molecular microscopic systems of coal pores. In front of the mining and excavation working face, the gas pressure and content increase, the coal body is damaged, and the coal body stress increases. This also explains that this area is prone to coal and gas outburst.