Fungal-induced water repellency in sand

Salifu, E. and El Mountassir, G. (2020) Fungal-induced water repellency in sand. Géotechnique. pp. 1-22. ISSN 0016-8505 (In Press)

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    Water infiltration into granular soils and the associated pore water pressure increase and reduction in shear strength can trigger landslides, instability of vertical cuts and failure of retaining walls. Water repellent soils can reduce infiltration to maintain soil suction. Recent research has demonstrated the creation of synthetic water repellent soils using chemical methods. This paper investigates a biological treatment for creating water repellent sand via the growth of the fungus Pleurotus ostreatus. Water repellency was assessed using: (i) water drop penetration test, (ii) molarity of ethanol drop test and (iii) modified sessile drop method with contact angle (θ) determination via image analysis. Fungal-induced water repellency was found to be ‘extreme’ (θ >110°) up to 4 weeks and 'severe' (θ > 105°) up to12 weeks, even with no further supply of moisture or nutrients. A water repellent layer was formed and maintained in saturated conditions, which is difficult to achieve using chemical methods.