Abstract:In order to solve the problem of full-section trenchless construction without temporary support and soil reinforcement in shallow overburden of water-rich soft soil layer in central urban area, the theoretical basis and research direction of underground bundled integrated tunnel（U-BIT）method suitable for Shanghai are provide by investigating and comparing Japanese MMST, URT and PCR methods in terms of the feasibility of shallow overburden, the diversity of the section, and the sealing of water. This method is based on the design idea of the combined temporary initial support and permanent structure. After the pipe-curtain is jacked, through the tensioning ring prestressing, the original longitudinal jacked and discrete steel pipes with small cross-section are bundled together to form a complete force system that can be transversely loaded with cross-section diversity, high efficiency in construction, environmentally friendly, and high utilization rate of the excavation section. This method has been successfully applied for the first time in the project of Shanghai Metro Line 14 Wuding Station. It has achieved fast, silent, low-disturbance and low-deformation construction of underground structure with shallow overburden in central urban area in water-rich soft soil layer, making an outstanding contribution to the promotion of the great leap from "impossible to implement" to "friendly construction" for urban underground infrastructure which the excavation construction cannot be implemented.
