Strength of Recompacted Loess Affected by Coupling between Acid–Base Pollution and Freeze–Thaw Cycles

Abstract

To study how the coupling between acid–base pollution and freeze–thaw cycles (FTCs) affects the shear-strength properties of recompacted loess, soil specimens are subjected to direct shear tests after FTCs. The experimental results indicate that of the cohesion and internal friction angle of polluted soil, the former is much more likely to be affected by FTCs. The cohesion deteriorates significantly with more FTCs, and this is the main reason for the change in soil strength, i.e., the acid–base pollution acts to increase the soil strength, but the FTCs act to reduce it. The strength indexes of soil specimens with different concentrations of chemical solution after FTCs are also different. The order of the coupling effect on the soil strength is secondary pollution > primary pollution > no pollution. The composition of the soil specimens differs with the order in which the chemical solutions are added, thereby leading to differences in the apparent and strength characteristics of the soil after FTCs. It is concluded that consideration must be given to the impact of the change in soil strength properties after secondary pollution in seasonal frozen areas.