Experimental study on physical and mechanical properties of sandstone after drying-wetting cycles of brine

The factors such as rainfall evaporation and groundwater fluctuation in Sichuan Province of China seriously affect the stability of slope engineering in the area. The deterioration laws of physical and mechanical parameters of saturated sandstone after different drying-wetting cycles (0, 5, 10 and 20 times) in brine (5%NaCl) solution are analyzed by conducting the triaxial compression tests. The damage mechanisms of the brine and drying-wetting cycles on saturated sandstone are revealed. The results show that the sandstone mass increases first and then decreases, while the permeability decreases first and then increases with the increase of the number of drying-wetting cycles. The threshold value for the mass change rate and permeability is 5 drying-wetting cycles. The peak strength, internal friction angle, cohesion and elastic modulus of the samples after drying-wetting cycles are all smaller than those of the dry sandstone. The peak strength and cohesion of the samples decrease gradually, while the internal friction angle decreases first and then increases with the increase of the cycles. The elastic modulus of the samples shows different trends with the increase of the confining pressure. The drying-wetting cycles have no significant effects on the failure mode of the sandstone, that is, the samples under uniaxial and triaxial compressions exhibit axial splitting and shear failure respectively. In the process of drying-wetting cycles, the mineral particles in the sandstone are gradually lost, resulting in the increase of the internal pores, which is the fundamental cause of inducing rock damage.