Characteristics of failure mass and safety factor during rainfall of an unsaturated slope

Abstract

Abstract.Water is an important factor triggering destabilization of soil masses in slopes, particular in unsaturated condition. Rainfall and snow melting are some of the main sources of natural water which frequently induce unsaturated slope failure in arid/semi-arid region or in active layers (i.e. frequently frozen/thawed layers) in permafrost. If the slopes are in coastal environment or adjacent to a stream, the soil materials from the sliding masses might be carried away by waves and currents, which can further lead to soil erosion problem. Therefore, characterization of the failure mass and safety factor is critical both for evaluation of slope failure hazard but also for erosion problem. This paper presents a method to study unsaturated slope stability including characterizing the size of failure and the safety factor by analyzing a theoretical unsaturated homogeneous slope subjected to rainfall infiltration. The slope is modelled numerically by the finite element method. A shear strength reduction technique is modified for unsaturated soils and employed to evaluate the factor of safety and the extent of the sliding mass. The results show that the size of failure and the factor of safety vary over the rainfall event. Notably, the extent of the sliding mass for unsaturated slopes depends strongly on the infiltration depth. Large global sliding surface tends to be the dominant mechanism if the infiltration depth is very shallow or very deep. Conversely, local restricted sliding surface becomes more dominant if the infiltration is approximately at a certain critical value.

The application of civic technologies in a field survey of landslides

“…Because it is difficult to access the inventory site, it is impossible to investigate the entire area of interest on the same scale using only one type of an image‐based contactless technology, and using data generated by different aircrafts and using different techniques is recommended for achieving a precise digital terrain model (Hsieh, Chan, & Hu, ; Le et al, ). Two research objectives are addressed in this article based on the precise results from previous studies conducted using smartphone global navigation satellite system (GNSS) positioning in forests (e.g., Tomaštík, Tomaštík, Saloň, & Piroh, ) and the potential applications of civic technologies, specifically the Lenovo Phab 2, for landslide mapping.…”

“…Slope failures are one of the major natural hazards worldwide (Le, Gallipoli, Sanchez, & Wheeler, ). Integral use of alternative technologies for the identification and effective assessment of natural hazards might contribute to the prevention of land degradation in many endangered areas (Raouf, Peng, & Shah, ).…”