Test study on permeability properties of the sandstone specimen under triaxial stress condition

AbstractDuring the formation of mining space, the stress of rock within the scope of disturbance of mining redistributes, and a range of rock in front of and on the both sides of tunnel is damaged under concentration stress. Due to the change of the stress, some of cracks in damaged rock open and the others close, which greatly affects the flow of gas in rock. The change and development of cracks in rock and the unusual flow of gas are two main reasons that cause all kinds of gas accidents to happen in roadways. Based on this fact, a water seepage test was conducted in a sandstone specimen under triaxial stress condition by using MTS815.02 Electro-Hydraulic Servo-controlled Rock Mechanics Testing System. During the test, the deformation parameters and permeability of the specimen at twelve testing points were measured. Through the analysis of experimental results from a macroscopic perspective, the laws that the permeability changed respectively with axial strain, hoop strain and volumetric strain in the completely stress-strain process of the sandstone specimen were obtained. By comparison of influences of axial strain and hoop strain on the permeability in the completely stress-strain process of the sandstone specimen, it was concluded that hoop strain dominated the change of permeability at elastic stage and plastic stage of rock deformation under triaxial stress