Shallow Slope Stability Analysis Method for Vegetated Slope

Abstract

Based on direct shear tests of soil samples with roots, the empirical formula of roots’ contribution to soil’s shear strength is summarized. In consideration of the effects of sliding surface depth, sliding mass width, sliding mass shape and roots, shallow slope stability analysis method for vegetated slope is suggested by mechanical equilibrium analysis of shallow sliding mass. According to the analysis of factors affecting shallow slope stabilization, it is shown that the factor’s importance descending order is sliding mass width, sliding surface depth and sliding mass shape in turn. Results of shallow slope stability analysis proposed by the paper are reasonable in comparison to the plane analysis method because more factors are taken into account. INTRODUCTION Numerous researchers have verified that plant roots can increase the shear strength of shallow soils, thereby enhance the stability of shallow slope ( e.g., Gray 1978; Wu 1979; Waldron 1981; Abe 1991). Many researchers have also derived various analytical models of soil-root interaction and shallow slope stability. However, they are mostly focused on the influence of vertical roots on shallow slope stability, and analyze the shallow slope stability by the plane method (e.g., Koler 1998; Sidle 1992; Ekanayake 1999; Zhao 2006; Qi 2006; Deng 2007). In fact, vertical roots can not reach the failure surface, therefore, they do not significantly improve the stability of shallow slope in most cases. In recent years, people have realized that lateral roots can improve the stability of shallow slope (e.g. Zhou 1997). Nevertheless, the analytical method is far from mature. We summarize the empirical formula of roots’ contribution to soil’s shear strength, then put forward shallow slope stability analysis method for vegetated slope according to mechanical analysis of shallow sliding mass. INFLUENCE OF PLANT ROOTS ON SOIL’S SHEAR STRENGTH Direct shear tests and results Prior to the test, we screen sandy clay with 2 mm soil samples sieve, then put sieved soil into different pots and compact them, finally remodel the soil by water addition. In