Evaluating the significance of saturation in shallow landslide failure: saturated–unsaturated soil perspective

Abstract

Landslides present a complex challenge within the field of soil geotechnics, particularly in the context of partially saturated soil. Throughout the entire range of saturation, the soil encounters both negative and positive pore water pressure. Understanding the transition from negative to positive pore water pressure is necessary as it significantly impacts the strength of the soil. However, the determination of suction during shear tests presents difficulties, limiting the utilization of unsaturated shear strength. To address these challenges, this study conducted a comprehensive investigation into the problem of saturated–unsaturated landslide failure. The research primarily focused on examining the influence of water saturation on soil strength and stability, with a specific emphasis on the role of suction and pore water pressure. The findings show the significant contribution of suction in imparting strength to the soil within its saturation range. Notably, a direct correlation between water saturation and unsaturated shear strength was not observed due to the distinct relationships between suction, pore water pressure, and saturation. The shear parameters were found to decrease with increasing saturation. Additionally, a transition in the failure mode of the soil was observed, shifting from brittle plastic to plastic failure. Furthermore, the investigation of landslide stability under different saturation levels highlighted the importance of soil suction and pore water pressure. The comprehensive investigation of the study provides valuable insights into the relationship between water saturation and soil behavior with reference to land slope failure.