关键词: 圆形基坑, 围护结构, 变形, 超深基坑判定

Abstract: With the fast development of economic and social progress, human beings urgently need to develop and utilize the underground space. The resulting super-size engineering projects also promote higher requirements for the design theory, construction method and construction management technology of the related underground engineering. In this case, the diaphragm wall has become the first choice for the supporting structure of many deep excavation projects, and the shape characteristics of the diaphragm wall have also developed from the traditional straight line to the form of curved, circular, and other complicated shapes. To promote the research on the deep and large foundation excavation projects, based on an actual engineering project in Xi'an, the PLAXIS 3D is used to simulate under three-dimensional, various subsurface and loading conditions. The feasibility of the three-dimensional finite element software is validated. The deformation characteristics of the deep excavation supporting structure, the change of the lateral earth pressure behind the supporting wall, the internal force in the diaphragm wall and the influence range of the surrounding environment of the deep excavation are evaluated. The deformation criteria of the circular and ultra-deep excavation are proposed. The results indicate that the lateral deformation of the supporting structure of the circular deep excavation is very small, but it demonstrates that the deformation trend of “medium bulging”. Due to the arch effect in the circular supporting structure, the bending moment in the diaphragm wall is small, and the circumferential axial stress is much greater than that of in the radial axial stress. The structure is mainly in compression, which can take the advantage of the high compressive strength of concrete materials. Under such working conditions, the influence range of the circular deep excavation on the surrounding environment is twice as the excavation depth. The deformation of the ultra-deep excavation can be estimated from the excavation depth, excavation diameter and the stiffness of the supporting structure through a fitting coefficient n. The results show that, when the excavation depth is large, the mechanical performance of the circular supporting structure is better and has little impact on the surrounding environment. Its characteristics can be reasonably used to optimize the deep excavation and to improve the monitoring of internal force, deformation and settlement during the construction.

Key words: Circular Deep Excavation, Supporting Structure, Deformation, Deformation of Ultra Deep Excavation