Laboratory investigation of plant root reinforcement on the mechanical behaviour and collapse potential of loess soil

Abstract

Plant roots reinforcement as a bioengineering approach in ground modification, can be very productive in stabilizing problematic soils. The present study is an attempt to offer new insights into the effect of soil-Vetiver root reinforcement on shear strength and collapse potential of loess soils using laboratory investigations. A program of direct shear and collapse potential tests considering three root area ratios, RAR (1, 3 and 5%), three sampling depths, SD (30, 60 and 90 cm), two root distributions, RD (1 and 4) and two plant ages, PA (2 and 4 months) is performed in this study. Results indicate that Vetiver root can increase the soils internal friction angle up to 49% in addition to increasing cohesion value up to 3.23 times. ‏It is noteworthy that the process of increasing the shear strength has not always been accompanied by increase in RAR values so that reducing shear strength of the samples by increasing RAR values from 3 to 5% confirmed this. The findings also reveal that planted soil specimens with grouped root arrangement had a better reinforcing mechanism compared to the single one. It has been shown that plant roots are very efficient in reducing collapse potential up to 36%.