Effect of grass on soil reinforcement and shear strength

Abstract

Plants are used to reduce erosion and stabilise slopes in many places. The present paper discusses the reinforcement effect of two different types of grass (Cynodon dactylon and Imperata cylindrica) roots with soil. Root distributions are also investigated with depth and lateral directions. The shear strength test is conducted to understand the root interaction system with soil. Pull-out tests are performed for Imperata cylindrica to investigate the interaction of roots with soil. The increased shear strength is calculated by a large shear box instrument (30 cm 3 30 cm 3 15 cm). The results show that the roots significantly increase the shear strength of soil. This is primarily dependent on the properties of the roots and their profile. The increased shear strength owing to Imperata cylindrica and Cynodon dactylon grass is 36 kPa and 11 kPa respectively. Relative shear strength is also defined and used to quantify the reinforcement capacity of grasses. The relative shear strength owing to Imperata cylindrica grass is around three, whereas that owing to Cynodon dactylon grass is approximately two.