Abstract:Based on the ratio test, the specimens for simulating sandstone type salt rock of different grades and consisting of cement, river sand, salt and water were made. The leaching experiment was carried out to explore the evolution rules of the concentration of the leaching solution. The leaching mechanism of salt and kinetics of the multi-phase reaction were analyzed. Shrinking core model and regional reaction model were used to fit the leaching process, and the effects of leaching on uniaxial compressive strength and its failure type were analyzed. The results show that, with the increase of leaching time, the concentration of the leaching solution goes through three stages: exponential growth phase, linear growth phase and stable phase. The leaching of salt is a procedure under the function of dissolution and crystallization, with concentration gradient of solute being the essential motivating force. The higher the grade of specimen, the more obvious the exponential growth phase, and the sharper the slope of the linear growth phase. The leaching rate also has the similar three phases as the concentration of the leaching solution, but the higher the grade, the lower the final leaching rate. The modified shrinking core model and regional reaction model can be used to fit the concentration curves of leaching solution. The uniaxial compressive strength (UCS) of the sample increases a little after leaching, however, the failure type of which does not change, and all of them are single bevel shear compression failure.

Key words: solution mining; salt rock; kinetic model; leaching rate