A novel modeling approach for the simulation of soil–water interaction in a highly plastic clay

Abstract

Formulation of unsaturated soil properties in a mathematical form is necessary for the computational modeling of water flow in soil deposits. To achieve this objective, it is essential to determine the soil–water characteristic curve (SWCC) in order to identify the soil response to transient water flow conditions. The volume–mass constitutive surfaces are other key properties that provide an overall theoretical framework for the soil state variables. In this paper, a bimodal SWCC equation was developed for a native clay deposit based on laboratory soil moisture-suction measurements. The proposed bimodal SWCC equation was formulated based on two distinct logistic power regression models. A factor quantifying the change in the soil hydraulic conductivity was also used to simulate the increase in the hydraulic conductivity of a cracked soil structure. The constitutive surfaces were then established based on the developed bimodal SWCC and representative consolidation test results. This study also attempted to perform an unsaturated seepage modeling analysis using the developed mathematical framework. The model was utilized to simulate the application of net surface flux on a soil column consisting of a highly plastic clay over a clay till. The sensitivity of the seepage analysis, attributable to variations in the SWCC and the hydraulic characteristics, was demonstrated. The results showed that the SWCC is a critical property controlling the modeling of the soil–water interaction, and it has a theoretical weight in performing a water seepage analysis. The use of a bimodal SWCC was capable of capturing the behavior of the top cracked clay layer leading to a rapid change in the volumetric water content with time.