The Effects On Tunnel In EPB Shield Adjacent Constructing

In this paper, we take the shield tunnel in Suzhou Subway Line No.1 as project background. In consider of reasonable excavation by steps, stress releasing coefficient, shield force and grouting, the security and construction affects of EPB shield tunneling adjacent construction are analyzed, with the purpose of proposing reasonable suggestions on diplopore and parallel shield tunnel construction. The main research contents are as followings:1. Review the standard of parallel shield tunnel approaching construction, the stability judgment criterion of existing tunnels, the control measures and prediction methods of shield tunnel construction. The prediction formula of the earth surface settlement based on modified Perk-method and stochastic medium theory are introduced respectively.2. According to the characteristics of shield tunnel, we simplify shield tunnel as the homogeneous cylinder. Then through determining the reasonable shield-jacking force, the releasing coefficient and grouting thickness, the major steps and key links in shield tunnel construction are defined.3. Using Midas-GTS to carry out 3D numerical analysis of approaching construction of shield tunnel. Study the influence of the under construction tunnels on the existing ones by simulating the process of parallel shield tunnel construction. The rules of earth surface settlement, rock stress, the surrounding rock pressure and internal force distribution of existing tunnels, which are influenced by the stress releasing coefficient and grouting, are revealed.4. Using Midas-GTS to carry out 2D numerical analysis of approaching construction of shield tunnel. Compare the difference of internal force between the 3D-analysis and 2D-analysis, and explain it.According to the results of FEM analysis, summarize the rules in the approaching construction of shield tunnels, with the purpose of solving the problems in the course of construction in difficult and special areas.