Centrifuge modeling of layered rock slopes susceptible to block-flexure toppling failure

Abstract

Block-flexure toppling failure is a widespread issue in natural and excavated rock slopes. The aim of this paper was to elucidate the failure mechanism of block-flexure toppling failure using a centrifuge model. The artificial rock and a slope model were prepared. A series of mechanical tests (i.e., uniaxial compression tests, direct shear tests, and three-point bending tests) were then conducted to research the properties of the artificial rock. Three kinds of measurement methods (laser displacement meters (LDMs), digital image correlation (DIC), and fiber Bragg gratings (FBGs)) were used to acquire detailed information on the deformation and failure process associated with block-flexure toppling failure. The results of our test show that block-flexure toppling failure occurs instantaneously and that the total failure surface is stepped. More explicitly, the preceding section of the failure surface is a flat plane perpendicular to the joints that dip steeply into the face in front of the slope crest. The rear of the failure surface begins to become stepped and the heights of the steps are mainly controlled by the spacing of cross joints. The deformation and failure zone can be divided into three subzones: a toppling failure zone, a crack zone, and a deformation zone. The tensile stress in the continuous columns shows a distribution that is similar to a triangle. That is, the value of the tensile stress on the top of each column is approximately zero and gradually increases with the burial depth of the column. The tensile stress in the columns at the back of the slope is less than that in the face of the slope.