Research on the Formation and Development of Plastic Zones in Surrounding Rocks of Roadways Containing Gas

Considering that the gas in the gas-containing roadway has an important influence on the deformation and failure of the surrounding rock, based on the law of gas migration in the rock mass, a mathematical model of fluid–solid coupling of gas-containing coal and rock is established. Through numerical simulation, the distribution of gas in roadway containing gas and the formation and development of plastic zone of surrounding rock are studied. Research results: (1) The shape of the plastic zone of the surrounding rock of the gas-containing roadway is determined by the in-situ stress. With the increase of the principal stress ratio, the plastic zone of the surrounding rock transforms from a circle to an ellipse, and finally into a butterfly shape. (2) With the increase of the principal stress ratio of the roadway, the plastic zone of the surrounding rock of the gas-containing roadway gradually develops into a butterfly shape. The volume of the plastic zone continues to increase, and the rate of increase continues to accelerate. (3) With the increase of the principal stress ratio of the roadway, the shape of the plastic zone in front of the excavation work of the gas-containing roadway has obvious differences. The circular or elliptical plastic zone has a small leading distance in front of the excavation face, and the section shrinkage rate of the plastic zone is slow, and the overall shape is truncated cone. The butterfly plastic zone has a large leading distance in front of the excavation face, and the section shrinkage rate of the plastic zone is fast. Therefore, when the speed of roadway excavation is relatively fast, it is easy to cause accidents such as coal and gas outburst in front of the butterfly blades in the butterfly plastic zone and the excavation work.