Quantitative Analysis of Seismic Response of Rock Slopes Using Discontinuous Deformation Analysis — A Case Study

For the prevention and mitigation of hazards, it is crucial to quantitatively analyze the seismic response of rock slopes. However, only a few studies have quantitatively analyzed the seismic response of rock slopes; these studies have considered topographic effects only and have neglected geological site effects, such as impedance contrasts and fractures, which are important factors affecting the seismic response of rock slopes, as revealed by multiple recent phenomena. Therefore, this study primarily aims to investigate the possibility of employing a numerical model for quantitatively analyzing the seismic response of rock slopes by considering the geological site effects. Herein, a discrete element method, i.e., discontinuous deformation analysis (DDA), was employed for the dynamic analyses, and a well-monitored rock slope, Mount Dong, was selected as the case study. In the proposed DDA model, horizontal and vertical ground motions were applied simultaneously. The different weathering degrees of the Mount Dong rock layers were considered to reflect the impedance contrasts, and the penalty value at the fractures was altered according to the stiffness for reflecting the fracture effects. Furthermore, a set of optimal boundary settings, especially for DDA, were applied to handle seismic dynamic problems. Results show that DDA can quantitatively reflect the seismic response of Mount Dong along a single direction, such as the horizontal direction, which is sufficient to satisfy engineering requirements. The peak ground acceleration amplification analyses indicate that: 1) a strong impedance contrast is more important than topographic effects for the seismic response of Mount Dong; and 2) in addition to the impedance of rock layers, widely spread fractures also play an important role in contributing to the seismic response anisotropy of rock slopes. Finally, spectral amplification analyses reveal that the responses of the inner and surface portion of Mount Dong are significant in a low- and high-frequency range, respectively.