Soil water retention mechanisms and implications to soil mechanical behavior

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Soil water retention mechanisms and implications to soil mechanical behavior

Dr. Idil Akin
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING, WASHINGTON STATE UNIVERSITY

Soil-water retention mechanisms are directly linked to fundamental properties such as mineralogy and surface area and have an important influence on macroscopic soil hydraulic and mechanical behavior. The dominant water retention mechanism at low saturation is surface hydration and is particularly important for fine-grained soils or materials with active surfaces. The dominant water retention mechanism at high saturation is capillarity and is particularly important for coarse-grained soils. Transition in these water retention mechanisms and the impact to internal stress state and corresponding soil behavior remain poorly understood. The dependency of mechanical behavior on water retention mechanisms is explained through tensile strength, resilient modulus and small strain shear modulus measurements over a wide range of saturation and applications to climate change related geohazards are discussed. Particular focus is given on post-wildfire slope stability (i.e., erosion, wetting-induced shallow landslides, debris flows). The preliminary results of a study that was the first effort towards understanding the fundamental changes in soil behavior post-wildfire over time and implications to hillslope stability are presented. Surficial stabilization alternatives to control post-wildfire erosion and associated debris flows are discussed. Vision for future work to address post-wildfire slope stability issues to help generate fire-resilient communities is presented.

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