Study on Deterioration of Strength Parameters of Sandstone Under the Action of Dry–Wet Cycles in Acid and Alkaline Environment

Abstract

In order to study the deterioration of strength parameters of sandstone under the action of dry–wet cycles in acid and alkaline environment, laboratory tests were conducted on the sandstone specimens for 1, 3, 6 and 10 dry–wet cycles in the solutions with a pH value of 4, 7 and 9, respectively. With the strength data recorded after each cycle, the Mohr–Coulomb strength criterion parameters and the Hoek–Brown strength criterion parameters were obtained. First, the rock deterioration was briefly analyzed. Then, the failure envelopes and the failure surface on the $\pi$ plane at different pH values after different cycles were graphed. The results show that the parameters decrease with the increase in dry–wet cycles. The deterioration is most serious when the number of cycles is small, and then becomes moderate. In addition, the deterioration coefficient of the sandstone is the largest in acidic environment ($\hbox {pH}=4$), followed by that in alkaline environment ($\hbox {pH}=9$) and that in neutral environment ($\hbox {pH}=7$). The deterioration effects of drying and wetting on the following parameters are as follows: fitting compressive strength > cohesion > material constant > internal friction angle. When the pH value of the soaking solution changes from 7 to 4, the deterioration coefficients of the fitting compressive strength and cohesion rise by 30%, while those of the material constant and internal friction angle rise by 10%.