Determination of unsaturated hydraulic conductivity of sandy soils: a new pore network approach
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RESEARCH PAPER
Determination of unsaturated hydraulic conductivity of sandy soils: a new pore network approach Behrooz Daneshian1 • Ghassem Habibagahi1 • Ehsan Nikooee1 Received: 14 May 2020 / Accepted: 1 October 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. Keywords Pore network modeling Relative hydraulic conductivity Soil water retention curve Unsaturated soils
1 Introduction A core ingredient of the frameworks used to model unsaturated flow in geomaterials, the slope stability, earth pressure analysis under unsaturated seepage conditions, rainfall-induced landslides, and seepage analysis of earth dams is the unsaturated hydraulic conductivity function [10, 12, 26, 51]. Moreover, modeling the hydromechanical and thermohydromechanical behavior of unsaturated geomaterials necessitates proper models of unsaturated hydraulic conductivity [40, 62].
& Ehsan Nikooee [email protected] Behrooz Daneshian [email protected] Ghassem Habibagahi [email protected] 1
Department of Civil and Environmental Engineering, School of Engineering, Shiraz University, 71348-51156Zand Street, Shiraz, Iran
Experimental measurement of unsaturated hydraulic conductivity function is, however, time-consuming and a difficult task [54, 56]. To date, various equations for estimating unsaturated hydraulic conductivity have, therefore, been proposed. They can be mainly categorized into two groups (Table 1): equations which are purely empirical in nature, and equations which are obtained following a conceptual model. Purely empirical models often either incorporate coefficients, which have no physical meaning, or are built based on experiments limited to some specific
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