Effect of pH on Physical and Mechanical Properties and Microstructure of Collapsible Loess

Acid-base pollution seriously affects the long-term stability of geotechnical engineering. Unconfined compressive strength, collapsibility test, and shear strength test were used to study the effect of different pH values on the physical and mechanical properties of loess. XRD and SEM were used to further explore the mechanism of the effect of different pH values on loess. The test results showed that compared with the control group (pH=7), the decrease in pH led to a significant decrease in the intensity of the diffraction peaks of the mineral components, and the proportion of medium and large pores in pH=3 and pH=5 was 93.3% and 89.9% respectively, which in turn led to a decrease in the unconfined compressive strength, collapsibility, and shear strength. With the increase of pH, a large amount of gelling material is generated in the alkaline environment and the intensity of the diffraction peak of mineral composition increases. Compared with pH=7, the micropores and small pores of pH=9 and pH=11 increase by 25.0% and 59.96% respectively, which improves the physical and mechanical properties of the loess. Acid pollution will reduce the physical and mechanical properties of loess, but alkali pollution can improve the physical and mechanical properties of loess, which can provide a reference basis for the prevention and control of acid and alkali pollution in loess areas.