Abstract: The internal support system has a wide applications in various deep excavation engineering projects. This paper presents the deep excavation support case history of the Shenzhen Headquarter Building of China National Offshore Oil Co. (CNOOC).  The design approaches of deep excavation near the metro alignment are presented. The secant pile combined with the doublecircle internal supporting system is adopted in this project. Using the popular geotechnical commercial software PLAXIS, the mechanical behaviors and the deformation characteristics of the retaining structure and internal supports are thoroughly investigated. In comparison of the computational and the construction monitoring results, it is demonstrated that the design approach of the 'doublecircle internal supporting system' can not only meet the retaining structure safety requirements and cost effectiveness but also satisfy the demanding requirements of the adjacent surrounding structures and facilities.

Key words: Reclamation Area, Metro, Double-circle Lateral Support, Deep Excavation