Laboratory investigation on mechanical and hydraulic properties of sandstone under freeze–thaw cycle

In the process of mine construction using artificial ground freezing, the rock mass in the frozen walls experiences frost heaving damage during freezing. After thawing, the water penetration into shaft lining can be a serious problem. This paper reports about a set of stress–seepage coupling experiments that were carried out to investigate the mechanical and permeability characteristics of the sandstone induced by freeze–thaw loading process under various confining pressures. The experimental results indicated that the elastic modulus and the peak stress of the sandstone increases along with confining pressure, however, there are no obvious changes in Poisson’s ratio and axial strain at the peak stress. If the confining pressure is held at a constant value, the elastic modulus and the peak stress of the sandstone decrease as the confining stress in the freeze–thaw loading process (referred to as freeze–thaw pressure) increases. The permeability and volume strain of the sandstone are evidently correlated under the confining pressure of 6 MPa. During the loading process, the volumetric change of the sandstone consists of three stages, i.e., first compaction, second rapid expansion and finally stabilization. Accordingly, permeability also demonstrates three stages: first, slight decrease, second, rapid increase, and finally, stabilization or slight decrease. During the loading process, there is no evident correlation between the permeability and volume strain of the sandstone under the confining pressure of 12 MPa, 18 MPa, and 24 MPa due to the formation of compaction bands and compacting shear bands. The initial permeability of the sandstone decreases as the confining pressure increases but increases together with the freeze–thaw confining pressure.