Test Studies On The Surface Friction Characteristics Of 4 Kinds Of Plant Roots-Soil

The plant root system has strong effects on soil reinforcement. The friction characteristics of root - soil interface affect soil reinforcement of root system. In this paper, based on the direct shear test and pull-out test on the interface between soil-soil and soil-roots of Artemisia sphaerocephala ,Caragana intermedia , Salix psammophila and Sabina valgaris ,friction characteristic of the interface was studied, and the primary factors of influence frictional resistance characteristic of root -soil interface were analyzed in Wind and Wate Complex Erosion Area in Inner Mongolia .we got the following conclusions:The shear relationship of interface between soil and 4 kinds of pant root is similar to soil–soil interface, which obeys to the Mohr-Coulomb theory.In the main distribution layer, although the cohesive strength of interface between the soil-roots is inferior to soil-soil, the friction characteristic reverses. The shear strength of soil-roots because of the friction coefficient increasing, is stronger than the soil-soil, it indicates that the cementing property of roots-soil is higher than that of soil-soil. Friction coefficient, cohesive strength and shear strength of interface between soil and 4 kinds of plant root are increased with the dry density of soil increasing. The effect on friction coefficient, cohesive strength and shear strength of interface between soil and 4 plants root of soil moisture content is similar to pure soil. Friction coefficient of them is decreased and cohesive strength of them are increased and then decreased with water content of soil increasing. In saturated soil (soil moisture content 33.2%), the shear stress stability value of 4 plants root - soil interface≥soil-soil interface , it indicates that the cementing property of roots-soil is higher than that of soil-soil.4 kinds of plants single root the largest pull-out force is increasing and pull-out shear strength of root–root interface is increasing and decreasing with the root diameter increasing. It indicates that the cementing property of fine is better than coarse rootThe pull-out shear strength of Root - soil interface is growing and then decreasing with of soil moisture content increasing and increasing with dry density of soil increased, which agrees with the result of direct shear test ; with the tensile speed increased, the shear strength of root - soil interface is reduced and then growing .Four kinds of plant compared, friction coefficient, cohesive strength and shear strength of Artemisia sphaerocephala and Caragana intermedia root-soil interface>Salix psammophil root-soil interface>Sabina valgaris root-soil interface.So far as the friction characteristics are concerned, Soil reinforcement of Artemisia sphaerocephala and Caragana intermedia roots is better than that of Salix psammophila roots. Salix psammophila is better than Sabina valgaris.