Study on the mechanical properties of clayey slip zone soil considering montmorillonite content

Abstract The strength property of slip zone soil determines the evolution mechanism and deformation damage of landslides. When the slip zone soil contains a certain amount of hydrophilic minerals, it, therefore, has swelling properties. These swelling properties cause the mechanical property of cohesive slip zone soils to differ from those of conventional-type of slip zone soils. Thus, four cases of typical landslide cohesive slip zone soils in the Shanxi Province of the Yellow River Basin were used as research objects to study the mechanism of hydrophilic minerals on the mechanical properties of cohesive slip zone soils. The mineral fractions of the cohesive slip zone soils were analyzed using X-ray diffraction tests, followed by direct shear tests to analyze the pattern of the shear strength parameters of cohesive slip zone soils under different hydrophilic mineral contents with water content. Finally, the free swelling rate test was used to verify that montmorillonite minerals are the main hydrophilic minerals affecting the swelling characteristics of cohesive slip zone soils. The results were as follows. The cohesion and internal friction angle of clayey slipband soils exhibited two patterns (negative exponential/negative correlation) with the variation of water content, and the critical values of the pattern of the variation of the shear strength parameters with water content were affected by montmorillonite content ranging from 17.65% to 34.52%. The shear strength attenuation of clayey slip zone soils showed a positive correlation with the change in montmorillonite content, and the swelling property caused by montmorillonite minerals was the intrinsic reason for the shear strength attenuation of clayey slip zone soils under different water content conditions. The research results explain the shear strength decay law of cohesive slip zone soils from the perspective of mineral composition and reveal the unique strength properties of these slip zone soils.