Abstract: Based on visualized pull-out system and digital photogrammetry measurement technology, pull-out tests were carried out for five kinds of coarse-grained soils with different coarse-grained contents (mass percentage of particles with particle size>5 mm). The effects of coarse-grained content on the interface strength index, particle displacement evolution and geogrid strain were discussed. The test results show that the interface cohesion c and the interface friction angle increase with increasing in different degrees. When increases from 20% to 35%, the pull-out displacements of geogrid corresponding to the peak value of strain and pull-out force at the end of geogrid decrease, but the geogrid strain increases at each section; with the increase of , the displacement vector direction of coarse-grained soil particles tends to be horizontal, and the displacement decreases significantly. At the same time, the void of the interface between reinforcement and soil decreases obviously. The increase of reduces the displacement of coarse-grained soil particles at the interface of reinforcement and soil, while the range of indirect influence zone expands, which indirectly drives coarse-grained soil particles within a certain height range, and increases the cohesive force of the interface at macroscopic scale. With the increase of , the maximum displacement velocity of soil particles at the V3 interface decreases. The maximum displacement velocities of soil particles at V1 and V2 in the indirect influence area increase slightly due to the expansion of the indirect influence area and the strengthening of particle disturbance.

Key words: coarse particle content, geogrid, interfacial strength, geogrid strain, digital photogrammetry measurement technolog