Insights into the impact of synergistic fungi-biopolymer stabilization on the shear strength of sand

In the past decade, there have been several studies on the geotechnical strength of biopolymer-treated soils. These studies indicated that a major disadvantage of biopolymer treatment is its inability to maintain adequate strength upon soil saturation. To address this drawback, a new stabilization technique has recently been explored whereby biopolymer addition is combined with the inoculation of fungi. The synergic application of fungi and biopolymers to soil stabilization is a novel and promising approach but it remains to be fully validated. In this study, an experimental campaign was carried out to identify the best nutrient media among sugar, honey and Guar gum while exploring the best fungi-biopolymer combination for soil stabilization. The shear strength of a treated sand was investigated by direct shear tests at different stages of fungal growth. Test results indicated that sugar is the best nutrient due to a simple structure that is easily broken down by fungi. Moreover, the combination of 5% fungal liquid suspension (obtained from 2% solid fungal spawn and 3% sugar) and 1.5% biopolymer (Xanthan gum) appeared optimal for enhancing soil cohesion.