Friction Characteristics of Soil-Soil Interface and Root-Soil Interface of Caragana Intermedia and Salix Psammophila

Using a direct shear test on soil-soil interface and root-soil interface of Caragana intermedia and Salix psammophila, friction characteristics of the interface was examined, and the influences of normal stress, dry density of soil and soil moisture content on friction characteristics were analyzed. The results showed that, the shear characteristics of root-soil interface of Caragana intermedia and Salix psammophila obeys to the Mohr-Coulomb theory. Friction coefficient of root-soil interface of Caragana intermedia and Salix psammophila increased with increasing dry density of soil. The effects of soil moisture content on friction coefficient and cohesive strength at root-soil interface of Caragana intermedia and Salix psammophila was similar to that in pure soil. With increasing soil moisture content, friction coefficient decreased, and cohesive strength increased firstly, and then decreased. In the main roots distribution layer, although the cohesive strength of root-soil interface was inferior to soil-soil, the shear strength of root-soil interface was stronger than that of soil-soil because of increasing friction coefficient. It indicated that the capacity of resisting displacement at root-soil interface was higher than that at soil-soil. So far as the friction characteristics were concerned, soil reinforcement of Caragana intermedia roots was better than that of Salix psammophila roots.