Calculation Model of the Uplift Movement of a Shield Tunnel during Construction in Soft Soil
(1 Department of Civil Engineering, Hebei Jiaotong Vocational and Technical College, Shijiazhuang 050091; 2 School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043; 3 School of Civil Engineering, Southwest Jiaotong University,Chengdu 610031)
Abstract：
The uplift mechanism of a segment is analyzed, and the load distribution law of a calculation model for segment uplift during shield tunnel construction is determined. There are some problems if the elastic support method and modified routine method are directly applied to the design of a shield tunnel during uplifting: calculations by the elastic support method show that segment bottom moves downward and doesn′t conform to the actual conditions of segment uplift, while the modified routine method doesn′t consider the reverse compress characteristics of the overflying soil mass at the tunnel crown. Based on the elastic support method and thoughts of a modified routine method, a mechanical model of reversal resistance is set up. The results show the proposed calculation model agrees very well with the characteristics of segment uplift during construction. The maximum and minimum values of the bending moment, axial force and shear force under the state of segment uplift during construction increase by 68%,21%, 51%, and 34%, 69%, 22%, respectively, compared with the elastic support method and modified routine method, which shows that segment damage and cracking or leaking caused by inadequate reinforcement can be avoided with the proposed design method for an uplift segment.
2018, Vol. 55 