Impact of Deep Foundation Pit Covered-excavation Reverse Construction in Water-rich Sand Layers on Surrounding Environment

［Objective］With the continuous advancement of urban modernization in China, the available space within cities is becoming increasingly scarce. Deep foundation pits are often constructed in environmentally sensitive areas, inevitably making impact on the surrounding environment. This is particularly true for deep foundation pits in areas with thick, water-rich sand layers, where improper construction control can easily lead to severe hazards. Therefore, it is necessary to study the impact of deep foundation pit covered-excavation reverse construction in water-rich sand layers on the surrounding environment. ［Method］Using Shenyang North Railway Station on Shenyang Metro Line 4 as an example, the deformation impact of deep foundation pit construction on the above-ground buildings, underground structures, underground pipelines, and power corridors is analyzed through construction monitoring method. ［Result & Conclusion］In the initial stages of excavation, the above-ground buildings primarily exhibit settlement deformation. As the excavation depth increases, settlement deformation gradually decreases, eventually presenting as upheaval deformation. The deformation of underground structures is significantly affected by the position of the excavation face, with maximum deformation occurring when the excavation face approaches the foundation buried depth of the structures. Underground pipelines show a clear positional impact, with the deformation of the right-side pipelines being much greater than that of the left-side pipelines, both primarily exhibiting settlement deformation. The deformation of power corridors is closely related to foundation pit excavation depth. When the excavation depth is relatively shallow, the power corridors are largely unaffected, but during the excavation of the fourth underground level of the station, the deformation of the power corridors begins to increase gradually.