Progressive failure mechanical behaviour and response characteristics of sandstone under stress-seepage coupling

Abstract

Abstract Conventional triaxial loading tests with different confining pressures and stress-seepage coupling tests on sandstone with different confining pressures and seepage pressures were conducted. A permeability model considering strength and strain was established, which better characterized the progressive deformation mechanical behaviour of sandstone under stress-seepage coupling. The results showed the following. (i) The confining pressure not only affects the peak strength of sandstone but also affects the axial deformation under conventional triaxial loading conditions. (ii) Compared with the seepage pressure effect, the degree of the confining pressure effect on the strength of sandstone was weaker, but the degree of that on the axial, radial and volumetric deformations of sandstone was stronger under stress-seepage coupling. (iii) With increasing confining pressure, the axial strain of sandstone decreased, while the corresponding radial and volumetric strains showed progressively increasing evolution characteristics under identical seepage pressures and different confining pressures. With increasing seepage pressure, the axial strain continuously decreased, while the corresponding radial and volumetric strains showed the progressive evolution characteristic of first increasing and then decreasing under identical confining pressures and different seepage pressures. (iv) Compared with the confining pressure effect, the degree of the seepage pressure effect on the permeability progressive evolution law of sandstone was weaker under stress-seepage coupling. The research conclusions could enrich the theories for the prevention and control of water inrush accidents in coal mines.