A numerical approach for modeling crack closure and infiltrated flow in cracked soils

Abstract

Soil cracks generated in natural fields will change soil structure and provide pathways for preferential flow. Although most simulations have focused on the influences of surface cracks or subsurface cracks in the fields, few studies are conducted on the deformable cracks extending from soil surface to deep soil layer. The present study addresses a fundamental issue and investigates the differences in water flow during infiltration processes of deformable and non-deformable cracked soils. Based on the discrete crack network model, a two-dimensional numerical approach is proposed to investigate the preferential flow in deformable cracked soil. Numerical simulations on water flow are implemented for matrix domain and cracks with the finite element method, which are discretized into solid elements and zero thickness elements, respectively. The proposed model is validated through explicit modeling and experimental observation and then compared with deformable crack approach. It is further employed to simulate the infiltration process of deformable cracked soil revealing significant differences in infiltration characteristics between deformable and non-deformable cracked soils, even if the cracks all act as preferential flow pathways. Although the saturation in crack closure of numerical model is variable during infiltration process, the effect of saturation is still affected by the number of cracks. Furthermore, cracks do not entirely close over a long period of infiltration, and thus they can become preferential flow pathways in subsequent infiltration events. These findings highlight the gap in simulations of water infiltration in cracked soil and the potential for erroneous simulations of water condition when cracks cannot be deformable during infiltration process.