Experiment on the stability of granular soil slopes by rainfall infiltration

Abstract

Slope failure is commonly caused by rainfall infiltration due to increase in pore-water pressure within the slope. In order to understand the failure mechanism of granular soil slopes, a model slope subjected to rainfall in ltration was developed and employed to perform experiment on sandy soils. Different geological conditions, fines contents of sand, and rainfall intensities were considered as variables. Infiltration of rainfall was simulated by an overland ow infiltrating uniformly into a platform on the top of the slope. During the experiment, the variations in pore water pressure and volumetric water content in the soil were measured. The characteristics of the failure mechanism and the responses of pore pressure and water content in four model slopes were observed and discussed. According to the observation, the failure in permeable sand was a sliding mode. Initial failure was noticed as a piping occurred at the toe of slope, and it then gradually propagated upward as a retrogressive failure. However, the failure in less permeable silty sand was initiated by erosion at shallow depth, the rill later expanded and turned into either a flow or a complex mode of flow and slide, depending on the rainfall intensity applied. Moreover, sandy soil had a marked increase in porewater pressure when approaching failure; but this phenomenon was less obvious in silty sand.