Evaluating the Influence of Surface Characteristics on Shear Strength of Sand-Fines Mixture Soil-Foundation Interface

To investigate the influence of surface characteristics on the shear strength of sand-fines mixture soil-foundation interface, a modified shear box was utilized. In this study, a smooth and two textured (or rough) surfaces that simulate conventional and innovative foundation elements were used, and the soil-surfaces interface was subjected to monotonic shear loading. The soil used in the present study is a mixture of medium sand and fine-grained soils. Two sand-fines mixtures were prepared (i.e., 100% sand–0% fines and 60% sand–40% fines). The results presented herein show that the increase in roughness level of tested surfaces leads to an increase in the interface shear resistance when compared to smooth condition. The higher interface resistance of textured (or rough) surface could be attributed to the creation of highly confined soil wedges (passive zones) at the face of elements and soil dilation with the displacement of surfaces against interface soil at a constant rate. The percentage of increase was up to 68.5% for 100% sand–0% fines mixture and 75.0% for 60% sand–40% fines mixture soils when compared to the interface resistance of smooth surface, respectively. The findings of the present study encourage the adoption of foundation elements with a textured (or rough) surface in sites consisting of sand-fines mixture soils.