Preliminary observations of the shear behaviour of fungal treated soil

¹ University of Strathclyde, Department of Civil and Environmental Engineering, Glasgow, UK
² Università di Napoli, Dipartimento di Ingegneria Civile, Edile e Ambientale, Federico II, Italy

^* Corresponding author: emmanuel.salifu@strath.ac.uk

Abstract

This paper presents results of an investigation into an entirely novel technique for ground improvement involving the use of fungal hyphae. Fungal hyphae (long filamentous branches) are known to contribute to soil aggregation and soil hydrophobicity, and are hypothesised to also influence the hydro-mechanical behaviour of soil. We present here preliminary observations of the mechanical behaviour of sands treated with the fungal species Pleurotus ostreatus (P. ostreatus). Direct shear tests were carried out on sand containing different percentages of organic substrate (the nutrient source for fungal growth) and treated with P. ostreatus. The stress-strain behaviour of fungal treated and untreated soil was investigated. Results show that irrespective of the percentage of organic matter, fungal treated specimens tended to show a loss in the peak behaviour characteristic of the untreated control specimens and an associated transition towards a more contractive volumetric response. The limited experiments conducted to date appear to indicate that the main factor responsible for the differences in behaviour between treated and untreated specimens is due to lubrication of the grains by the fungal hyphae and exudates. Further investigation is required to fully elucidate the mechanisms influencing the mechanical behaviour of fungal-treated soils.