Extreme climatic events in the 21st century threaten the resilience of geotechnical engineering structures. Low-permeability barriers are at a particularly high risk of inundation under ﬂooding or cracking during droughts, compromising the barriers and permitting contamination of the surrounding ground. Water repellent (WR) granular soils (Figure 1) present an innovative solution to this problem [1, 2, 3]. Hydrophobisation can arise naturally (e.g., due to deposition of organic matter, treatment with wastewater or wildﬁre), but can also be achieved in laboratory conditions by chemical treatment, typically with dimethyldichlorosilane (DMDCS). Besides being resilient to volumetric change under changes in saturation, water repellent soils have been shown to slow down water and root penetration, thus making them a potential candidate for waste storage liners. However, the eﬀect of water repellency on soil strength and permeability is not well understood (Figure 2). This new PhD project will examine the fundamental behaviour of WR soils and how they can be used in the ﬁeld.
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