Mechanical response of root-reinforced loess with various water contents

Abstract

The control of erosion process is an important issue in China, particularly in the northwest of China, in which loess erosion is a widespread problem with environmental and social consequences. Previous studies have shown the benefits of root-reinforced soil to control the erosion by increasing the shear strength of soil. In this study, we have investigated the shear strength of loess reinforced with root by carrying out consolidated-undrained triaxial tests. The effect of Robinia pseucdoacacia root distribution patterns including horizontal, vertical and crossed reinforcement on the shear strength is explored under 16% water content by weight and saturated condition, which represent natural water content and saturated condition that soil would experience, respectively. The results show that root insertion in loess causes a distinctive increase in strength of specimen under consolidated-undrained condition for the whole range of water content studied. Compared with unreinforced specimen, the increase of internal cohesion contributes the most to the increase in strength of reinforced specimen. The internal friction angles of root-reinforced specimens, however, are hardly affected by root insertion and root distribution patterns. Furthermore, in comparison with the horizontal and vertical reinforcement patterns, the crossed reinforced pattern is found to be the most effective distribution pattern against shear failure in loess. Its shear strength increment is greater than that with the vertically reinforced root loess, followed by the horizontally reinforced root pattern. In general, the water content increment of loess greatly reduces the strength of both root-reinforced and unreinforced loess.