ABSTRACT
Metropolitan Expressway Route K7, Yokohama North Line, is 8.2km long expressway. 70% of total length was designed as tunnel structure, in order to minimize house transfer as well as to reserve local environment. 5.5km long twin tunnels were constructed with EPB TBMs. There are 4 bifurcations that connect to ramp tunnels under another contract, and there are the number of houses above the bifurcations, thus a trench less construction method was required. Therefore, the method of enlargement/widening technology was developed and applied in constructing the bifurcation, and which was a global first application in actual project. It consists of Enlargement Shield Tunneling and Large Diameter Pipe Roofing. This technology enabled the bifurcation construction without any adverse impact on the residential environment above.
