Flow exchange and unsaturated permeability of cracked clay: experimental and modelling

Abstract

Cohesive soil was often submitted to the shrinkage when it is dried. Constrained shrinkage and heterogeneity of the soil in terms of density or porosity and water content conduct to cracks of the fine soil. The unsaturated permeability as a function of suction changes significantly with cracks number and opening. The paper aims to study the flow exchange flow in the unsaturated cracked clay flow, by measurement of the unsaturated permeability using tensiometer and hygrometer sensors in cracked specimens under drying and controlled in an environmental chamber. The instantaneous profile method was used to interpret these tests. Cracks were characterised by Image Analysis which conducted to define some known quantitative parameters as the Cracks Intensity Factor (CIF). Aiming at reproducing the experimental results, the paper presents a model which leads to the prediction of the suction field and the flow rate exchange. This model integrates analytical equations of the unsaturated permeability and water retention property of the cracked soil and also the shrinkage behaviour. A good agreement between numerical and experimental results is highlighted in terms of flow exchange rate.