Geological structures, such as fault, geological discontinuity, and weak rock formation are likely to play a critical role in the stability and behaviour of rock slopes. However, the impact of such geological structures on the mining-induced deformation of rock slopes in an open-pit mine remains unclear. This study takes an open-pit limestone quarry in Japan as an example to discuss the mechanical interaction between specific geological structures. In this quarry, below the mining area is a vertical fault intersecting with a weak rock formation almost parallel to the slope surface. Based on these unique geological structures, numerical simulations are conducted in the framework of discrete element method while considering different geological situations to elucidate the impact of each geological structure. The analysis results show that the vertical fault and weak rock formation significantly impact the deformation of the rock slope during mining progression. In the case of a fault-only model, no slip occurs. However, in the case of the fault and weak rock formation model, as the mining face is crossing the fault, apparent slip occurs along the weak rock formation. In this model, although the vertical fault constrains the sliding of the upper discontinuities at the early stage, the normal stress of the weak rock formation decreases gradually as the mining progresses, and local shear failure occurs at the intersection of the weak rock formation and fault, which leads to the slip. However, rock slope displacement due to the slip gradually decreases and eventually stabilizes as the working face gets away from the vertical fault. This study provides new insight into the deformation mechanism of the rock slope and serves as a reference for future mining and slope prevention work.
Assessing slope stability is a critical part of mining and civil engineering projects. This is especially important for large open-pit mines and rock slope engineering because slope failure results in a delay in production and may cause fatality and equipment loss. In this regard, it is common to evaluate the stability of an open-pit mine based on the deformation behaviour of the rock mass (Kodama et al. 2009). Among factors affecting open-pit mine deformation including excavation (Najib et al. 2015), geological structures are significant due to their unique mechanical characteristics. Therefore, a number of studies on the influence of geological structures have been undertaken in recent years. Such studies indicate that geological discontinuities such as faults, and their properties, including shear strength, slope face angle (αf), and friction angle, determine the failure mechanism. For example, if a potential failure plane daylights on the slope face at an angle smaller than the slope face angle and greater than the angle of friction, the kinematic condition is satisfied, and failure can take place (Raghuvanshi 2019). In the study, the impact of weak rock formation has been examined as a unique rock material. Zhao et al. (2020) also indicate that a weak rock formation often affects the stability of the rock slope because of its creep behaviour.
