Cyclic behavior of root-loess composites under direct simple shear test conditions and insights from discrete element method modeling

Abstract

Plant roots are widely known to provide mechanical reinforcement to soils against shearing and further increase slope stability. However, whether roots provide reinforcement to loess cyclic re-sistance and how various factors affect roots reinforcement during seismic loading have rarely been studied. The objective is to conduct a series of cyclic direct simple shear tests and DEM numerical simulation to investigate the cyclic behaviour of rooted loess. The effects of initial static shear stress and loading frequency on the cyclic resistance of root-soil composites were first investigated. After that, cyclic direct simple shear simulations at constant volume were carried out based on the discrete element method(PFC3D) to investigate the effects of root geome-try, mechanical traits and root-soil bond strength on the cyclic strength of rooted loess. It was discovered that the roots could effectively improve the cyclic resistance of loess. The cyclic resistance of the root-soil composite decreases with the increase of the initial shear stress, then increases, and improves with the increase of the frequency. The simulation result show that increases in root elastic modulus and root-soil interfacial bond strength can all enhance the cyclic resistance of root-soil composites, and the maximum cyclic resistance of the root-soil composite was obtained when the initial inclination angle of the root system was 90°.

Keywords

root-soil composite / cyclic direct simple shear tests / PFC~(3D)

Funding

Key Research, Development and Transformation Projects of Qinghai Science and Technology Department in Qinghai Province(2022-SF-159)