Measured and Predicted Unsaturated Permeability of Cracked Compacted Fine Soil

Abstract

The unsaturated permeability of cracked compacted fine soil is a key parameter in geotechnical engineering, particularly when analyzing water flow through the soil in various conditions. The compaction affects the saturated and unsaturated permeability by reducing porosity. However, cracks can appear by shrinkage and growth during desiccation, which obviously leads to macro-porosity (a process during which the soil acquires a high level of double porosity). The development of a crack network influences the suction (as negative water pressure) and then the unsaturated permeability. The current paper aims to analyze the role of the crack network (considered as macropores) on the unsaturated permeability, by quantifying the network based on the Crack Intensity Factor (CIF). The unsaturated permeability is given as a function, separately of CIF and suction. The experimental results may be considered constructive for soil modeling. Regarding the birth of the first crack, it occurred when the suction reached a value near to that of the air entry suction. Since the first crack appeared, primary cracks were developed and then followed by secondary cracks. The obtained experimental results of WRC and Kunsat for cracked compacted clay are beneficial in managing the design of the geotechnical structure stability and the environmental issues of water diffusion. CIF increases with suction, which is augmented during the drying process demonstrating a decrease in the moisture content. After 21 hours of desiccation, CIF ended up reaching a value of 4%. It is generally recognized that cracks create preferential pathways for water flow, whereas their geometry and distribution influence how water moves through the soil. Modeling the impact of cracks on permeability may involve considering factors like crack width, orientation, and connectivity. In this paper, a simple model was proposed to predict the unsaturated permeability as a function of suction with different CIF values with the material being assumed as a double porosity soil.