Experimental Modelling for the Effect of Rainfall and Earthquake on Slope Stability of Engineered Fill

Abstract

The collapse of several houses in some residential developments in Sendai during the M9 Tohoku earthquake warranted the health monitoring of several slopes in southern California. Majority of the houses developed in southern California are in engineered fill and the qualities of compaction may not be sufficiently checked. Due to recent trend of unpredictable rainfall and being located in the high seismic activity area, houses constructed on slopes in southern CA have strong potential to slide during earthquake or heavy rainfall. This study involves a systematic study of an engineered fill at Mission Viejo, California for potential slide activities. The materials borrowed from the site were compacted in a Plexiglass container at the field density, moisture content, and field slope angle. The slope was poured with the 100 year return period rainfall expected in the area using, a rain simulator. Variation in suction in the soil mass was recorded with duration of rainfall. Slope stability analyses were performed to evaluate the effect of earthquake in those slopes in reducing the factor of safety. The study result shows that the combined effect of antecedent rainfall and seismic shaking has significantly high effect on slope stability, compared to strong magnitudes of either rainfall or seismic acceleration acting separately.