ABSTRACT
An important aspect of landslide investigation is to determine and evaluate shear strength of the soils in the field or in the laboratory. One of the many in-situ techniques is the Borehole Shear Test (BST) which can directly measure soil shear strength parameter values. This chapter presents a case history using the BST as the in-situ test method to investigate a landslide involving glacial till in Iowa, USA. Shear strength values of the soil were measured on the walls of boreholes using an in-situ BST. The BST and Ring Shear Test were employed for a landslide investigation, and the shear strength values obtained were used in the slope stability analyses. Shear strength values of the soils were also estimated from back-calculations based on the slope giving unity factor of safety. The shear stresses versus displacements at various test stages for the samples were plotted to determine the corresponding ultimate shear stresses.
