Experimental determination of shear resistance of clays

Soil shear strength parameters are very important in usage for engineering design. The consolidated-drained triaxial compression test,direct shear box test and ring shear test are the well-known methods to obtain the residuel and peak strengths parameters in the laboratory.In this study; direct shear box test, ring shear test and consolidated-drained triaxial compression test were performed to determine shear strength parameters, specifically the internal friction angle. Correlations were developed to estimate friction angle from liquid limit, plastic limit, plasticity index, liquid limit, clay fraction and activity index. It is determined that residual and peak shear strength, obtained from different test methods with increasing plasticity index, plastic limit, clay fraction and activity index. Also, direct shear test and ring shear test were contucted three different shearing rates in order to investigate the displacement rate effect on peak strength. Direct shear test and ring shear test were performed on identical samples under same vertical stresses. The obtained results were compared. It has also been observed that the peak friction angle obtained by the direct shear box test was greater than the one obtained by ring shear test.