Abstract: This study investigates a deep excavation project adjacent to sensitive environments, particularly focusing on complex surrounding conditions and uneven excavation depths. The construction site borders critically protected structures, including an operational shielded tunnel of Metro Line No. 13, a river floodwall, and high-voltage power pipelines, necessitating stringent environmental protection measures. Furthermore, the presence of a shallow highly permeable silt layer with hydraulic connectivity to the adjacent Shahe River significantly increases engineering challenges and risks. To ensure construction safety and environmental stability, the project implemented a zoned construction strategy following the principle of “shallow excavation first and near distance first.” Priority was given to constructing the shallow excavation adjacent to the metro tunnel to establish a stiff isolation barrier, thereby mitigating disturbances induced by subsequent deep excavation activities. A high-stiffness cruciform orthogonal bracing system was adopted to effectively control wall deformation, while a secondary support technique for sunken deep pits enhances the stability of the retaining structure. Field monitoring demonstrated that the proposed design measures were scientifically validated and effectively maintained all environmental impacts within safe and controllable thresholds throughout the construction process.

Key words: Adjacent to Subway, Deep Excavation, Shallow Excavation First, Environmental Protection, Secondary Support