Study on Mechanical and Permeability Characteristics of Containing Gas Coal-Rock Under Conventional Triaxial Compression

In this paper, the mechanical and permeability experiments of containing-gas raw coal and sandstone samples under conventional triaxial compression were carried out by using the thermal fluid solid coupling triaxial servo seepage experimental device. The results show that: the peak strength of containing-gas coal and rock increases linearly with the increase of confining pressure, and the strength of sandstone sample is much greater than that of raw coal sample. The complete stress–strain curve of containing-gas coal and rock can be roughly divided into compaction stage, linear elastic stage, yield stage and failure stage. When confining pressure is lower than 6 MPa, the permeability of raw coal sample decreases nonlinearly with the increase of axial stress. When the confining pressure is higher than 6 MPa, the permeability of gas in the compaction stage and linear elastic stage of raw coal sample is zero. The permeability of sandstone sample has no obvious change in the compaction stage, elastic deformation stage and yield stage. After failure, the permeability of sandstone increases sharply, and the permeability of sandstone post-peak decreases gradually with the increase of confining pressure.