Experimental investigations of fault reactivation induced by slope excavations in China

Abstract

Fault reactivation is a common and important engineering geological phenomenon. However, the surface expressions and intensity of reactivated faults adjacent to open-pit mines can vary with the engineering geological conditions. In this study, several types of fault reactivation were identified and studied based on geological investigations conducted at an open-pit mine in China. Based on these studies, a comparatively simple physical simulation method was employed to analyze the causes of fault reactivation under self-weight stress conditions. For a steeply dipping fault which outcrops in the tensile zone of an excavated slope, the tensile stresses generated perpendicular to the fault surface usually result in normal fault-style movement, regardless of the orientation of the fault. For a steeply dipping fault which outcrops in the compressional zone of an excavated slope, an outward-dipping fault usually generates reverse fault-style movement, whereas an inward-dipping fault usually generates normal fault-style movement. For a low-angled and inward-dipping fault, reverse fault-style movement could be induced because of the self-weight body forces of the hanging wall slope. Flexural toppling failure of an excavated slope was simulated by a series of inward-dipping faults. The simulated scarp sizes and deflections of the reactivated faults increased along the excavated slope.