关键词: 基坑开挖, 地铁隧道, 变形控制, HSS模型, 数值分析

Abstract: The super headquarters project of Shenzhen Evergrande center is located in the coastal soft soil area. It is also adjacent to a double-line shielded tunnel in the north with complicated surrounding construction conditions and therefore, the deep excavation construction has restrictive requirements for the deformation control. In order to study the impact of the ultra-deep excavation on the surrounding environment, a numerical analysis model of the adjacent subway side section is established with plaxis2D finite element software. The Hardening Soil with Small Strain (HSS) constitutive model and Mohr Coulomb (MC) elastic-plastic constitutive model are used in the analysis. The ground subsidence adjacent to the excavation, the deep horizontal displacement of the supporting structure, the soil layer deformation and the stress and deformation relations of the subway tunnel structure during the excavation of the foundation pit are evaluated. At the same time, based on the deformation control requirements, the application effect of the servo system on the deformation control of structures surrounding the deep excavation is analyzed under the three different supporting conditions; namely, conventional support, prestressed support without servo and prestressed support with servo. The analysis results indicate that the peak value of the ground subsidence adjacent to the excavation is concentrated at 0.2~0.3H (H is the excavation depth), and the peak value of the deep horizontal displacement of the supporting structure is concentrated at 0.6~0.7H after excavation, the main influence range on the subway tunnel structure is within 0.5H. Compared with the traditional supporting method, the prestressed servo support structure can effectively reduce the ground subsidence adjacent to the excavation, the displacement of the supporting structure. The new structure can also effectively control the stress and deformation of the tunnel structure, ensure the operation safety of the adjacent subway tunnel.

Key words: Deep Excavation, Subway Tunnel, Deformation Control, Hardening Soil with Small Strain (HSS) Model, Numerical Analysis