Analysis of push shear test without normal loading and its application

Push shear tests have often been used to determine shear strength of rocks or soils in investigation of landslides. However current analytical methods for a push shear test recommended in Handbook of Engineering Geology could not adequately derive parameters of the shear strength and should be improved. Data processing method is presented for the push shear test without normal loading based on the assumption of model's rigid body and no constraints along Y axis. A differential equation is established to represent the push shear test; and a set of equations is then derived for solving cohesion c, friction angle phi and curves of the shear failure surface. A case study is used to examine new formulas developed. Based on observed compression phenomena during in-situ test, the localized initial failure near the compression surface is analyzed. Causes for variation of the shear failure surface are explained. It is required that no constraints are applied to the compression surface along Y axis. In addition, the compression surface should be oriented perpendicular to the sliding or rotating surface. At the end, several issues related to push shear test are also discussed.