<p>Coastal deep excavation projects are often subjected to tidal fluctuations, which can significantly affect their deformation and stability. This study investigates the dynamic response of excavation sidewalls, surface settlement, and support structures under tidal effects using numerical simulations and field measurements. The results show that for a constant tidal period, horizontal displacement of the excavation sidewall increases with tidal range. Above the design excavation level, displacement increases with excavation depth, while below the design excavation level, it gradually decreases. For the same tidal range, the maximum horizontal displacement occurs below the excavation level and shifts upward as the tidal period shortens and downward as the tidal period increases. Surface settlement increases with tidal range, with the settlement peak consistently occurring 4 meters from the excavation. Surface settlement outside the excavation increases with excavation depth, initially rising and then decreasing as the horizontal distance from the excavation increases. Additionally, both concrete and steel supports experience increased axial forces with tidal range, with steel supports consistently bearing higher forces. These findings highlight the importance of considering tidal effects in the design and stability analysis of coastal excavations, providing critical insights to improve the safety and performance of such projects.</p>