The Effect of Clay-Soil on Landslide: Case Study from Central Java, Indonesia

Landslides are caused by triggering factors such as rainfall, geological factor, geotechnical properties of surface rock, and human activity. Weathering is an essential phenomenon that generates clay minerals and influences the landslide mechanism because the process will reduce rock mass resistance. In the study area, intensive rain contributed to the weathering and increased the water content in the clay soil that affected the stability of the slopes. The clay mineral in the soil in the study area was investigated. The type of clays was determined by plasticity index and liquid limit value and X-Ray diffraction analysis. Some geotechnical properties also were determined, including grain size, shear strength, and atterberg limit. As a result, the clay minerals within the study area’s volcanic rock formations play an important role in causing landslides because of illite and smectite, which reduce shear strengths and have high swelling potentials.