Research On Stress Characteristics Of Cut-and-Cover Framed Tunnel With Large Span Under The Lake

Abstract:Taking a wide view of the development of underwater traffic tunnel at home and abroad, there are a growing number of large-span tunnels to be built for the requirement of road traffic. Meanwhile, the problems of structural deformation and stability are becoming increasingly prominent. Therefore, research on mechanics characteristic of the tunnel structures is very meaningful.Based on Fangxing Lake tunnel project in Hefei, field testing and numerical analysis were used to study stress characteristics of tunnel structure, and its optimal design is discussed. The main research contents are as follows:(1) With field monitoring method, internal forces in the frame structure and its underlying uplift pipes and water pressure under the structure could be continuously acquired under every step of construction. All these data were summarized to get the stress distribution and its variation with construction to assess the safety of the structure.(2) Through laboratory tests, the physical and mechanical parameters of undisturbed soil were obtained. With a consideration of the structure-soil interface and fluid-solid coupling effect, the simulation model with the numerical analysis software ABAQUS was established to analyze the variation of tunnel stress corresponding to each construction stage. The mechanics characteristics were investigated by comparing the results obtained from field tests and numerical simulation.(3) Optimization design of tunnel structure was studied in the paper. Firstly, the effect of the fluid-solid coupling effect on tunnel structure was analyzed. Secondly, the behaviors of tunnel structures with different spans were compared. Thirdly, the study on optimal utilization of the uplift piles has been discussed.