Experimental Study On The Root-Soil Friction Mechanical of Typical Grasses With Soil Moisture In Purple Soil Bunds

[Aims] Bunds composed of plants with strong root systems have become one of the most important soil conservation measures for controlling soil erosion on sloping farmlands in the Three Gorges Reservoir area. In order to measure the friction characteristics of the root-soil interfaces to screen grasses for use in bunds to provide optimal soil bund protection. [Methods] The influences of interface, soil moisture and vertical load were examined by using direct shear friction and pull-out friction tests in the study. [Results] The results support the following conclusions. i) Friction characteristics were lower at interfaces in bulk soils than at root-soil interfaces. Direct friction characteristics were higher at the root-soil interface for goosegrass than other plants tested in this study. ii) The roots of grasses can substantially improve the soil shear strength under conditions of low (5%) and high soil moisture (25%). The relationships between friction characteristics and soil moisture can be described by binomial functions. iii) The constitutive relationship between the shear strength at the root-soil interface and vertical load can be described by a hyperbolic model that satisfies the Mohr-Coulomb criterion. The maximum pulling resistance was in the following order: goosegrass > barnyard grass > crabgrass . [Conclusions] Among the three grasses tested, the goosegrass root system has a highest resistance to deformation capability for soil conservation. These results can be used as references for understanding and controlling the friction characteristics and collapse of soil bunds in the Three Gorges Reservoir area.