Determination of unsaturated hydraulic conductivity of sandy soils: a new pore network approach

Hydraulic conductivity is one of the most important characteristics of unsaturated soils. Its determination is essential for modeling various phenomena of interest such as unsaturated flow and soil consolidation. Unsaturated hydraulic conductivity not only depends on the soil water content but also on the structure and connectivity of the pore space within the soil matrix. The common predictive models for unsaturated hydraulic conductivity do not account for the connectivity of different pores; instead, they are based on simplistic assumptions like the bundle of capillary tubes. Pore network models (PNMs) include connected structures of the pore space and, therefore, can better portray the realistic nature of the soil medium. In this research, a systematic approach is proposed to build pore network model to estimate the hydraulic conductivity of unsaturated soils. Major contribution of the study is to present how a predictive PNM can be constructed in the absence of sophisticated imaging data and solely based on the conventional soil data such as soil water retention curve. Finally, the results of pore network modeling show that despite the simple geometry of the proposed network, it has a relatively superior performance compared to the other available physically based models.