Dynamic Response of Hydraulic Tunnels Crossing Multiple Faults under Spatially Nonuniform Seismic Excitation

The dynamic response analysis of hydraulic tunnels in high-intensity seismic regions is often oversimplified in current research. Long tunnels crossing multiple faults, coupled with spatially nonuniform seismic excitation, pose significant hazards. This study introduces a comprehensive modeling methodology for tunnels intersecting multiple fault zones, incorporating multidimensional, multipoint random seismic excitation with intercomponent correlations. The results indicate that the tunnel response evolves progressively with increasing seismic intensity. For peak ground acceleration (PGA) ≤ 0.1g, displacement responses exhibit approximately linear proportionality to input motion, and no significant plastic deformation is observed. At PGA almost equal to 0.2g, localized plastic zones initiate, and displacement amplification increases markedly (up to 2.34 at Section S6), indicating the onset of nonlinear behavior. For higher intensities (PGA ≥ 0.3g), plastic zones expand substantially, and at 0.4g PGA, the maximum displacement reaches 12.33 cm with a plastic damage index of 5.07. Vertical displacements at the tunnel crown and invert are most sensitive to fault location, with Section S6 exhibiting the largest response. The plastic zone evolves from circular to elliptical, aligned with the fault dip angle, indicating fault-induced anisotropic stress redistribution. Increasing the number of fault intersections amplifies the peak displacement at the Fault-crossing section S6 by up to 49.30% (z-direction, PGA = 0.2g), while the plastic damage index rises by as much as 87.63%. These findings highlight the need to explicitly consider fault networks and intensity-dependent nonlinear effects in the seismic design of hydraulic tunnels.