Coupling effects of particle shape and cyclic shear history on shear properties of coarse-grained soil–geogrid interface

Abstract

Accurate measurement of particle shape is necessary to properly investigate the cyclic shear behavior of a soil–geogrid interface. In this study, the particle shapes of crushed limestone, quartz sand, round gravel and spherical granular media were described and quantified in terms of particle regularity. Cyclic direct shear tests were then performed with particles of various shapes for different relative densities and shear displacement amplitudes. Monotonic direct shear tests and post cyclic direct shear tests were performed to compare the relationship between particle regularity and interface friction angle. The test results showed that the interface underwent cyclic shear hardening for relative densities between 0.453 and 0.672. The area of the hysteresis loop, cyclic peak shear strength and maximum vertical displacement increased with increasing shear displacement amplitude, and decreased with increasing particle regularity. In monotonic and post cyclic direct tests, the friction angle decreased linearly as particle regularity increased. Comparing to the monotonic direct shear tests, the slope and intercept of the regression lines increased in the post cyclic direct shear tests after undergoing cyclic shearing. This study shows that it is important to analyze the interface shear behavior in the monotonic, cyclic and post cyclic direct shear tests using parameterized particle shapes.