Impact of bidirectional shaking on the seismic response of level and sloping ground sand deposits

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When conducting seismic site response analysis, typically only one of the shearing directions of the ground motions is considered. Existing research shows that neglecting the other components of the earthquake load can lead to an underestimation of the seismic demand. Currently, engineering practice loosely addresses this issue by a means of a rough scaling factor applied to unidirectional demand. However, recent studies have revealed that the impact of bidirectional shaking can be more challenging and significant, for both level and sloping grounds, increasing indices of performance such as settlement, liquefaction potential, and displacements, among others. The objective of this project is to investigate the effects of bidirectional shaking on the seismic response of sand deposits and to propose an evidence-based framework to account for it in engineering practice. Based on a verified and validated numerical approach, a database of nonlinear fully coupled three-dimensional analysis of sand deposits subjected to unidirectional and bidirectional seismic shearing will be developed to evaluate a wide range of scenarios. In collaboration with the industry partner BGC Engineering, different cases of the layered level and sloping ground conditions will be considered. The results will be compiled and analyzed to understand the effects of the bidirectional seismic shearing on the performance of the studied cases and to develop a well-informed simplified approach to account for that in engineering practice. The outcomes of this research and, in particular, the proposed framework, will be used by the industrial partner organization. This collaborative research will provide the engineering community in Canada with tools and means to improve the efficiency of the seismic design of major structures such as water dams and tailings storage facilities.