Unsaturated behavior of an earthfill dam during coupled initial impoundment and a prolonged rainfall

Abstract

Newly constructed earth-fill dams in a residual soil rich area have a high probability of failure occurrence in the first five years of operation. Monitoring a rate of the first impoundment of the dams is critical for monitoring the effectiveness and designed function of the dam over its service life. However, stability of the dams is uncertain under influential factors such as variability of soil properties of support foundations, simultaneous increases of water level in the upstream and infiltration in downstream dam surface from prolonged heavy rainfall event. In this study, failure mechanism for an earth-fill dam due to concurrent rises in water level upstream and rainfall infiltration was investigated using saturated-unsaturated soil principles. Seepage was analyzed using Finite Element Method and slope stability was analyzed using Limit Equilibrium Method. Results of the failure mechanism were compared and discussed with respect to varying stiffness of residual soil support foundation, coupled rising water reservoir and applied prolonged rainfall.