Effect of Gradation and Shape of Particles on Cyclic and Post-cyclic Interface Properties of Geotextile and Sand-Rubber Backfill

This research aims to investigate the dynamic interface properties between woven geotextile and granulated rubber-sand geo-composite using a set of cyclic and post-cyclic large-scale shear test. To this end, poorly graded sand having wide ranges of gradation, particle shape, and particle size was mixed with 25% proportion of granulated rubber and then subjected to the cyclic shear loading under different conditions of normal stress and displacement amplitude. The results demonstrate that, unlike sand-rubber composites, increasing the mean grain size of sand amplifies the interface shear stiffness between sand and geotextile. Additionally, an increase in the coefficient of uniformity reduces the interface damping ratio in both clean sand and sand-granulated rubber composites. Post-cyclic shear tests on sand-rubber composites also indicate that increasing the mean grain size boosts interface cohesion, while the interface friction angle is decreased. In addition, the samples containing a wide range of particle sizes (i.e., increasing the uniformity coefficient) have shown the lowest cohesion and friction angle along the sand-geotextile interface in all experiments.