Abstract: Sliding-zone soil is one of the most critical inherent factors that can affect the stability of landslide. A series of X-ray diffraction and mercury intrusion tests is conducted on the undisturbed sliding soil samples to obtain the composition and content as well as structure in the sliding-zone soil. The results show that the sliding-zone soil is mainly composed of quartz, labradorite, illite, etc, and the pores include mainly micropores and transition pores. Based on a practical landslide in which the pore water chemistry of the sliding-zone soil is variable, different chemical solutions are introduced as the saturating fluid. Through a series of tests including shear, permeability and scanning electron microscopy, variations of strength parameters, permeability and microstructure of sliding-zone soil are obtained. Variations of mechanical properties and permeability of the sliding-zone soil are analyzed. The results indicate that at the same pH value, the peak and residual strengths of soil soaked in the salt solution are larger compared to distilled water. However, under different pH conditions, introducing acid and alkali solutions as the saturating fluid can significantly reduce the strength parameters of sliding-zone soils. The results provide important data for both the analysis of the variation law of mechanical properties and the multifield coupling theoretical models of the sliding-zone soil under water chemical conditions.

Key words: landslide, sliding-zone soil, water chemical environment, physical and mechanical properties