Investigation of a landslide using borehole shear test and ring shear test

摘要

This paper presents a case history using the Borehole Shear Test (BST) as the in-situ test methodto investigate a landslide involving glacial till in Iowa,USA. Shear strength values of the soil were measured onthe walls ofboreholes using an in-situ BST. The investigation was supplemented by measuring the residual shearstrength values of the soil on remolded soil samples in the laboratory using the Ring Shear Test (RST). Backanalyses were also performed on the slope to evaluate the possible shear strength values and slope conditionsat failure. The results show that the average shear strength value of the soil obtained by the BST is comparablewith the residual strength value obtained by the RST and the shear strength value obtained by back-calculation.The slope failure could have occurred at a water table higher than that measured during the slope investigation,as the failed slope is stable under the currently slope geometry and water table conditions.