Evaluation of interface friction between cohesionless soil and common construction materials

A reliable quantitative assessment of interface friction parameters between construction materials and the surrounding soil mass where this interface represents a potential failure surface, will allow for less conservatism and/or safer design of soil-structures. This can only be achieved if the factors affecting the interface friction angle δ, are adequately understood. The purpose of this thesis is to obtain such an understanding. The influence of soil particle shape, confining pressure and amount of relative displacement on the value of δ are studied in the laboratory using a ring shear apparatus. Two quartz sands, one angular and the other rounded, with steel, concrete and geosynthetics were used as the interfacing constituents. Test data indicate that the value of δ can vary significantly for each of the surfaces investigated. Smooth HDPE geomembrane exhibits distinct peak and residual δ values that range from 65 to 90% of the friction angle of the surrounding sand. Rough HDPE and PVC geomembrane interfaces are shown to mobilize the full friction angle of the sand. Steel surfaces display a complex interface frictional response that is strongly affected by the amount of relative displacement along the interface. However, concrete surfaces mobilize essentially identical δ values at small and large displacements that are approximately equal to the Φ CV of the interfacing sand.Applied Science, Faculty ofCivil Engineering, Department ofGraduat