To investigate the mechanical property degradation laws of 6061-T6 aluminum alloy under the synergistic effect of coastal corrosive environments and cyclic loading, the effects of various corrosion durations (0 h, 600 h, 900 h, and 1200 h) on the static performance, hysteretic characteristics, and energy dissipation capacity of the material were studied through indoor accelerated salt spray corrosion tests, monotonic tensile tests, and multi-regime cyclic loading tests. The results indicate that after 1200 h of corrosion, the yield strength and ultimate strength decreased by an average of 2.28% and 5.16%, respectively, with the peak stress point shifting significantly forward. Corrosion significantly inhibits the cyclic hardening effect and accelerates the loss of ductility, with the ductility loss of 1200 h specimens reaching up to 44.0%. Strain is the key factor in activating the energy dissipation potential of the material; when the loading amplitude exceeds 4%, the energy dissipation coefficient stabilizes between 3.0 and 3.3. However, the combination of corrosion and random loading exacerbates the decay of energy dissipation capacity. This study aims to provide a theoretical foundation for the performance assessment and safety assurance of aluminum alloy structures in coastal engineering.

Under groundwater seepage, excavation disturbances in tunnels within weak surrounding rock easily trigger collapse accidents. This study, based on an actual tunnel project and considering fluid–solid coupling, establishes a three-dimensional numerical model of tunnel construction in weak surrounding rock, investigates the instability mechanisms of tunnel excavation under groundwater seepage, and optimizes tunnel support strategies. The results show that when fluid–solid coupling is considered, the deformation zone and stress concentration zone of the surrounding rock expand significantly, and peak stresses increase; initial support stresses generally increase, with the crown-bottom area being the most affected; a bedding dip of 22° causes a pronounced asymmetric distribution of deformation and stress in the surrounding rock, a feature further intensified under fluid–solid coupling; for circular excavation with a reserved core soil method, the optimal construction and support scheme is rock bolts 5 m long with a spacing (circumferential × longitudinal) of 0.9 × 0.85 m, forepoling microtubes 5.5 m long with a spacing (circumferential × longitudinal) of 0.6 × 2 m, and double-layer angles of 10° and 30°; after optimization, excavation disturbance is reduced, effectively limiting crown heave and lowering stresses in the waist surrounding rock. This study provides a reference for excavation control and support optimization for tunnels under similar geological conditions.