Arch action over an excavated pit on a stable scarp investigated by physical model tests

Abstract

Some slope failures along oblique faults experience arch to the extent that the stable scarp can be observed after collapse. The load resisting the scarp is transferred to the side supports by the circumferential forces across the exposed face, separating it from the force acting normal to the slope and the frictional resistance which runs along it. Therefore, the failure mechanism involves a passive condition where the major principal stresses dominate the force supporting the arches. This study presents the groundwork carried out to conˆrm the assumption of a passive condition appearing in the scarp of the inclined slope by measuring the pressure changes and the surface movement of a physical model. Moist sand was uniformly layered inside a rigid acrylic frame ˆxed on a slope and base made of rigid acrylic plates. The movement distributions of the slopes were recorded and analyzed using particle image velocimetry (PIV) and image processing software. As the toe of the slope was sliced and cut in sequence, starting from the middle part, the removal of the propped portion resulted in a slip along the surface. Since the moist sand fails inward rather than outward, it is reasonable to assume that the lateral compression is greater than the inclined compression, to the extent where it is su‹ cient to initiate arch action in a passive condition.