Influence of Matric Suction on the Shear Strength of a Cohesive Soil-Geosynthetic Strap Interface

This paper presents results and discusses the effects of seasonal climatic variations (wetting and drying) on shear strength of soil-geosynthetic straps interfaces under unsaturated conditions. The soil used for laboratory investigation was a compacted residual soil of gneiss composed of a silty-sand, from the Sao Paulo city, Brazil, and a high-tenacity polyester strap. Direct shear tests were conducted with three-different net normal stresses and levels of matric suction, besides the inundated condition. Results demonstrated that the cohesive soil used has excellent shear strength parameters, a high capacity to maintain negative pore water pressures and presents an efficient interaction with the geosynthetic strap. Furthermore, they indicate that the peak shear strength of the soil-geosynthetic interface increases nonlinearly with the soil suction, while the matric suction has a negligible effect on the post-peak shear strength of those interfaces.