Determination of soil shear properties on a soil to concrete interface using a direct shear box apparatus

Abstract

Direct shear experiments were carried out both to investigate the interaction between a predominantly cohesion less soil and in-situ concrete and the validation of the tangent of two-third of the angle of internal friction angle normally assumed in design involving stability of structures with respect to friction. The tests for soil to soil interface indicate internal friction angles of 13.9° and 14.3°, while the soil to in situ concrete interface indicates friction angles of 24.9° and 27.9°. For the soil–concrete interface; the tangent of two-third of the friction angles gives values that are developed by a range of normal stress indicated by the direct shear experiment. These values are between 141 and 430 kPa. The friction values computed from the soil–concrete interface are very conservative for this range of normal stress. However for normal stress values less than 141 kPa, the use of the tangent of two-third of the angle of internal friction principle may not be safe as it may overestimate the friction values which such a system will develop. The study indicates that a range of stress level should be specified for a given friction value adopted in a design situation.