Friction Properties of Interface between Soil-Roots and Soil-Soil of Artemisia sphaerocephala and Sabina valgaris

Through a series of direct shear tests on the interfaces between soil-soil and soil-roots of Artemisia sphaerocephala and Sabina valgaris, friction properties of the interface were examined, and the influence of normal stress, dry density of soil, water content of soil on friction properties were analyzed. The results showed that the shear relationship of interface between soil-roots of Artemisia sphaerocephala and Sabina valgaris obeys to the Mohr-Coulomb theory. Friction coefficient of interface between soil and roots of Artemisia sphaerocephala and Sabina valgaris is increased with the increasing of the dry density of the soil. The effect of soil moisture content on friction coefficient and cohesive strength of interface between soil-roots of Artemisia sphaerocephala and Sabina valgaris is similar to pure soil. Friction coefficient of them is decreased and cohesive strength are increased and then decreased with water content of soil increasing. In the main roots distribution layer, the cohesive strength of interface between the soil-roots is inferior to soil-soil, but the friction characteristic reverses. Because of the friction coefficient increasing, the shear strength of soil-roots is stronger than that of the soil-soil. This indicates that the cementing property of roots-soil is higher than that of soil-soil. So far as the friction characteristics are concerned, Soil reinforcement of Artemisia sphaerocephala roots is better than that of Sabina valgaris roots.