EXPERIMENTAL STUDY OF THE BEHAVIOUR OF INTERFACIAL SHEARING BETWEEN COHESIVE SOILS AND SOLID MATERIALS AT LARGE DISPLACEMENT

The assessment of piles lateral friction involves the determination of the interface shearing resistance at large displacement. Consequently, the shearing resistance mobilised at large displacements, at the interface between cohesive soils and steel and concrete of varying roughness has been studied in the ring shear apparatus. The latter is known to offer the best mean of studying shearing resistance when soils undergo large displacements. The focus of this work is to highlight the solid material surface roughness effect. Results obtained from soil-soil and soil-interface shearing tests are presented. They indicate that the surface roughness and the average diameter of particles, which are combined into the influence of relative roughness R, have a significant effect on the interfacial shear strength at a given normal stress level. With respect to R, three shearing modes are likely to take place: shearing at the interface, shearing within the soil and an intermediate mode involving these two types of shearing. For the second mode, the shear strength at the interface soil-rough solid materials (steel and concrete) is likely to be greater than the shear strength of the soil, particularly for soils whose major mineral component is montmorillonite.