This study provides an in-depth analysis of the deep excavation and support technology for the deep excavation of the Qunxian Road Extension to Xiaoshan Nanxiu Road Phase I project located in Keqiao District, Shaoxing. The project includes roadbed, bridge, and tunnel sections, with the tunnel section being approximately 2,190 m long. The study focuses on monitoring the impact of deep excavation on the vertical displacement of the surrounding ground surface, as well as the influence of hydrogeological and climatic characteristics on the project. The monitoring results show significant fluctuations in the cumulative changes and change rates at different monitoring points, but none exceeded the preset alarm values, indicating proper control of excavation stability. The maximum subsidence and uplift displacements were 7.2 mm and 13.1 mm, respectively. The vertical displacement change curves gradually stabilized over time, with the maximum subsidence rate decreasing from 0.89 mm/d to 0.02 mm/d. The study concludes that the deformation of deep excavations in highly permeable strata was effectively controlled, and the overall stability of the retaining structure was achieved, providing a reference for similar underwater bridge engineering design and construction.