Simple Method for Prediction of the Soil Collapse Behavior due to Wetting

It is widely accepted that the results of wetting tests conducted on collapsible soils by reducing matric suction in consecutive steps in the laboratory provide reliable experimental data for interpreting the soil collapse behavior. The variation of void ratio derived using such a testing technique is similar to that of water content in response to decrease associated with matric suction. For this reason, van Genuchten’s equation for the soil–water characteristic curve was extended to fit the measured data of collapse behavior to describe the variation of void ratio with matric suction. Two of the three fitting parameters in the extended equation, n and m, change negligibly with the applied stress, p whereas another parameter, α, could be represented as a power function of p at a given initial matric suction. For this reason, using the results of two wetting tests performed on identical soil specimens under different applied stresses, the power function is developed for α and the values of n and m are determined; thus, the collapse behavior can be predicted. A good agreement is observed between the collapse behavior predicted using the proposed method and the measured data on collapsible soils in the literature. The proposed method requires less experimental data and hence is simple for use in engineering practice applications.