Abstract: With the rapid development of the urban subway, more and more deep excavation for new projects needs to be installed in the safety protection zone of the active subway. The active Metro No 4 Line under passing the proposed OCT Wuhan Plot P (2018) 158 project. The distance between the supporting structure and the regional subway tunnel structure is only 11m, and the distance from the bottom of the deep excavation to the top of the subway tunnel varies from 2.6 to 8.2m. The surrounding environment of the deep excavation is extremely complicated, and the deformation control requirements for the excavation support structure are very restrictive, which poses great challenges to the design and construction. On the other hand, the soil fills up to 15 meters in height within the proposed excavated area needs to be unloaded. The control and remediation of the heaving deformation of the tunnel structure under unloading conditions is also an important part of this project. According to the characteristics of this project, the design of the deep excavation is based on the principles of safety, reliability, economic rationality, constructability, and construction schedule. For the first time in Wuhan area, the scheme of “upper unloading + soldier pile +a layer of reinforced concrete waler beam” is proposed and adopted in the deep excavation support design of the metro protection area. At the same time, to control the tunnel heaving deformation induced by the upper unloading of the regional subway tunnel, it is proposed to use perforated pipe grouting to reinforce the poor soil layer above the tunnel. The strength of the surrounding rock mass is effectively improved, and the heaving deformation of the subway tunnel during unloading is reduced. The monitoring data during the entire dep excavation construction process shows that all the monitoring data are within the allowable range and meet the requirements of the subway impact assessment, which can be used for the reference by similar projects.

Key words: Complex Environment, Deep Excavation Design, Subway Section Tunnel, Perforated Pipe Grouting, Monitoring Data