MMIJ Annual Meeting

Stability assessment of rock slopes is an important issue for open pit mines. Instability of rock slopes may result in slope failure, causing not only loss of production but also unexpected expenses for rehabilitation. Furthermore, fatal accidents may occur due to rock slope failure, making slope monitoring critically important in open-pit mining. To respond to these problems, factors which affect rock slope deformation have been investigated. Displacement of a natural slope is usually resulted from inelastic deformation such as sliding. However, displacement of a cut rock slope in an open-pit mine may be often induced by elastic deformation due to excavation. In previous studies, impact of regional rock stress on elastic deformation due to excavation was cleared. Effect of mining pattern on that was also investigated. However, the impact of geological formation including weak rock formation has not much cleared although geological formation is likely to affect the deformation. In this study, the impact of clay zone which is often seen in a limestone quarry was investigated by elastic analysis on 2-D numerical models with clay zone. Then, effects of dip angle, location and thickness of clay zone were analyzed by assuming Young’s modulus of clay zone is much lower than that of base rock. It is found that presence of clay zone does not change deformation mode of the rock slope but magnitude of displacement at rock surface is affected by feature of clay zone. Backward displacement is commonly seen in horizontal direction and magnitude of it depends on dip angle, location and thickness of clay zone.