Rapid estimation of residual shear strength by ring shear test

摘要

The residual shear strength of the soils is one of the main inputs for analyzing the stability of pre-failed slopes and the progressive failure problems, which generally occur in fissured clay slopes, caused by strength reduction with displacement. In practice, it is important to decide the residual shear strength parameters as quick as possible in an acceptable precision. The ring shear and the reversal direct shear tests are common methods to determine the residual strength parameters in the laboratory. The unlimited rotational shear, continuous displacement, constant cross-sectional area of the shear plane and uniform normal stress distribution during the test make the ring shear test more reliable than the reversal direct shear test to obtain the residual condition. This study presents the preliminary results of consolidated drained reversal direct shear and consolidated undrained ring shear tests carried out on twenty prepared soil samples having different clay fractions and plasticity indexes to determine residual shear strength parameters. The shear displacement rates were selected as 0.035 mm/min in reversal direct shear test and 20 mm/min in ring shear test. The relationship between residual shear strength angles of the tests illustrates that the ring shear tests performed at relatively high shearing rate are remarkable. The relationships between the residual shear strength angle, the liquid limit and the plasticity index were examined and obtained results were compared by the previous studies.