Studying the effect of desiccation cracking on the evaporation process of a Luvisol – From a small-scale experimental and numerical approach

Cracking formation due to desiccation of the soil surface is a common phenomenon related to the interaction between soil and the atmosphere. Indeed, during dry seasons, high evaporation of pore water near the soil surface leads to a more significant soil suction in this region. The suction results in compressive effective stress on the soil structure and produces shrinkage including cracking. As the crack network forms, the initial soil structure is strongly modified, which provides preferential flow pathways for solute-water and influences the soil hydraulic behaviour in general. The work aims to study the formation of cracks during evaporation process of a Cutanic Luvisol and evaluate how cracking affects the soil hydraulic behaviour. Laboratory experiments were performed on undisturbed soil samples. To do that, a small-scale environmental chamber was designed and equipped with sensors for measuring the ambient temperature and relative humidity, and a digital camera for investigating the initiation and propagation of cracks on the soil surface. By combining with a HYPROP device (UMS GmbH, Munich, Germany), the hydraulic properties and the kinetics of evaporation of soil samples were also determined through the tests. Finally, numerical simulations were carried out by using the finite element code LAGAMINE developed at the University of Liege to emphasize the effect of desiccation cracking on the soil hydraulic conductivity and the moisture transport mechanisms in the soil, as well as exchanges with ambient atmosphere.