Design and Construction of Enlarging Shield Tunnel Sections of Large Dimensional Shield Tunnels for the non-open-cut method

摘要

The use of the enlarging method for large dimensional shield tunnel construction is essential in thernbuilding of branch connections and ramps, particularly when constructing underground roads inrnnarrow urban areas. In this paper, the non-open-cut method, which excavates underground, used inrnThe Central Circular Shinjuku Route of Tokyo Metropolitan Expressway is reported.rnThis paper describes the construction of the cut and open of a part of steel segments installed in twoparallelrnlarge dimensional shield tunnels over a total length of 100 m using the non-open-cut method.rnThe pipe roofing method was adopted for three reasons: the excavation depth is relatively shallow; thernlocation is just beneath a trunk road intersection; and important utilities are laid underground atrnvarious locations. And, new construction methods such as use of pre-strutting, which involves thernplacement of preceding struts using pipe-jacking in order to stabilize the tunnels and to preventrndeformation, as well as preloading to reduce settlement of roof pipes are employed. Furthermore, inrnorder to ensure safety during the construction work and to reduce adverse environmental effects suchrnas ground settlement, various types of behavior prediction analysis have been carried out andrnmonitoring-feed backing to construction are performed as construction continues.