Research on cyclic loading-unloading triaxial test and fine microstructure of Guoyemoli landslide shear zone soil in Zhouqu

To reveal the effects of moisture content and confining pressure on the cyclic mechanical properties of soils in landslide shear zones, triaxial cyclic loading-unloading tests are conducted under different moisture contents and confining pressures, combined with scanning electron microscopy (SEM) for microstructural analysis. The experimental results show that three loading-unloading curves exhibit distinct hysteresis loops, and the resilient modulus is significantly affected by compaction degree and moisture content. Under the same compaction degree and confining pressure, the higher the moisture content, the larger the resilient modulus. Under the same moisture content and confining pressure (50 kPa), the higher the compaction degree, the larger the resilient modulus. When the samples approached saturation or the confining pressure increases to 100 kPa, the resilience phenomenon weakens significantly. SEM observations show that the clay minerals in the soil are arranged in an oriented manner, with the development of micropores and fissures, which led to an increase in porosity. Under the combined action of shear failure and groundwater, high pore water pressure is easily generated, thus inducing landslides. The microstructural characteristics can be used to invert the activity history and formation mechanism of landslides, providing a basis for landslide prevention and control as well as stability evaluation.