The Shear Strength of Q2 Loess in the Residual Tableland and Gully Area on the Loess Plateau under the Action of Drying and Wetting Cycles

ABSTRACT The shear strength of soil is influenced by drying and wetting cycles in practical engineering applications. This study focuses on the Q2 loess from the Xiaokongtong Valley in Qingyang City, specifically targeting the loess residual tableland and gully region. By using the direct shear test, we studied the shear strength parameters and the attenuation characteristics of shear strength in Longdong Q2 loess under different moisture contents and drying-wetting cycles. Using Longdong Q2 loess as an example, the results indicate that shear strength is inversely related to drying and wetting cycles and moisture content. In the context of more than three drying-wetting cycles, loess exhibited a reduced decrement in shear strength. The influence of these cycles was more pronounced on cohesion compared to the internal friction angle, with moisture content exerting an even greater effect on both parameters. Consequently, a functional relationship was established between the number of drying-wetting cycles, internal friction angle, and cohesion. This relationship facilitated the development of a shear strength formula, wherein the number of drying-wetting cycles was employed as the independent variable.