Estimating Strength Versus Location and Time in High-Plasticity Clays

Suction strongly influences the soil strength in slopes and earth structures constructed of high-plasticity clays. Strength degradation in earth structures can be explained in terms of moisture infiltrating into the soil mass, which reduces the suction and therefore strength of the soil. A moisture diffusion coefficient controls the rate of moisture diffusion into soil mass. Changes in suction during the life of a structure can be predicted from analytical and numerical solutions of the diffusion equation. This manual provides guidelines for predicting soil strength from estimated values of suction, estimating the moisture diffusion coefficient, and predicting suction as a function of location and time based on the estimated moisture diffusion coefficient. From these three steps, soil strength can be estimated as a function of location and time in slopes and earth structures.