A 3D SEM-FEM Multiscale Framework for Seismic Analysis of Hydraulic Tunnels Considering Source-to-Structure Simulation

The realistic prediction or simulation of the seismic behaviour of critical structures is highly sensitive to many aspects, including the earthquake source, propagation path, region topography, geological conditions and local complex structural dynamic analysis system. However, integrating the above key factors in a framework for generating realistic ground motions (GMs) and conducting dynamic analyses at specific engineering sites remains challenging. This task necessitates assessing the crucial elements involved in the seismic design of hydraulic tunnels (HTs), with the ultimate objective of safeguarding human lives in areas prone to seismic activity. To achieve this objective, a multiscale framework leveraging the spectral element method (SEM) and finite element method (FEM) is proposed. This framework involves establishing a coupling strategy between the SEM and FEM to address geological media–structure interaction problems. The SEM is utilised to generate and propagate elastic waves within the soil, while the FEM allows the studied structure to be comprehensively represented. The coupling technique is implemented using the weak-coupling strategy in conjunction with the time domain reduction method (DRM). Then, a series of dynamic analyses and seismic performance assessments of the HT with the coupling SEM-FEM method are conducted. The results indicate that (1) the nonlinear dynamic responses of the HT induced by the physical-based GM align with the recorded GMs, verifying the practicability of the proposed framework for source-to-HT simulation; (2) physical-based GMs of the hanging wall and foot wall, rupture fault distances and mountain locations can significantly impact the seismic performance of HTs.