An effective stress‑based parametric study on the seismic stability of unsaturated slopes with implications for preliminary microzonation

摘要

The stability of unsaturated slopes under seismic loading has become an important issue over the past few years which is the indication of its practical significance in geoengineering. This study aims at exploring the seismic stability of unsaturated sandy clay and silty clayey sand slopes using 2D limit equilibrium analysis for different slope geometries and ground water levels. To this end, the pseudo-static and the displacement-based sliding block Newmark's approaches are employed for parametric studies by considering the records of the 2003 earthquake that devastated the city of Bam, in the southeast of Iran. In all analyses, the unsaturated state of the soil materials is taken into account in accordance with the changes in the matric suction profile within the soil body using the effective stress approach of unsaturated soil mechanics. The research outcomes, in terms of the safety factor, are then analyzed and compared for different examined conditions. The parametric study in this research considered the method of analysis, slope geometry, ground water conditions, and soil type as the most influential parameters on the factor of safety. The results revealed that considering the unsaturated parameters for the examined soils results in higher factor of safety in comparison with the corresponding cases in which unsaturated parameters are not adopted. A comparative study was also carried out based on a threshold safety factor, in which the safety factors obtained from all analyses, undergoing various conditions and loadings, provide a preliminary insight into the prospective seismic microzonation of unsaturated slopes.