Research On The Interface Mechanics Characteristics Between Coarse-grained Soil And Geogirds

Coarse-grained soil is applied in engineering projects widely. Its shear strength characteristics and mechanical properties of the interface between coarse-grained soil and geogrid reinforcement material have become hot issues in present study.First, according to the characteristics of coarse-grained soil, a large scale direct shear test apparatus for coarse-grained soil was developed independently. Samples for the direct shear apparatus have a large size, which meet the requirements of coarse-grained soil, improve the accuracy of test results, and can successfully perform shear tests under dynamic loads, static loads, and complex shear paths.Second, one-way shear test results of coarse-grained soil and reinforced coarse-grained soil under different vertical load show that shear stress-shear displacement relationships of coarse-grained soil and reinforced coarse-grained soil are similar. Normal deformation shear displacement relationship of reinforced coarse-grained soil shows a dilatancy trend, and the lower vertical load is, the more obvious dilatancy is. Reinforced coarse-grained soil has a larger cohesion c and a lower internal friction Angle ψ than coarse-grained soil.Third, Applicability of hyperbolic model and index model, which are used to describe the shear stress-shear displacement relationship, was discussed, and a new shear stress expression which can depict strain softening was put forward.Fourth, Circular shear test results of reinforced coarse-grained soil show that, in circular shear tests, the normal deformation has shrinkage trend. Along with the increase of circulation number, circular tests of which amplitude are larger cause more serious damage to shear interface and have smaller accumulated residual deformations, and the strength of soil-geogrid interface decreases faster.Finally, dynamic circular shear test results of reinforced coarse-grained soil show that, the larger normal stress is, the bigger the average peak shear stress in a cycle is. Cohesion of shear interface decreases slightly, about lOkPa, during circular shear test. Internal friction angle declines dramatically from19°to approximately13°. Employing friction angle as damage parameter, the strength characteristic of soil-geogird interface under dynamic circular loads was investigated.