High Pressure Pipeline Project Within a Long and Deep Tunnelling Shield in Urban Area

Installation plan of diametrical pipeline within the existing circular trunk line was officially announced in 2002 as ‘Central Trunk Line’;- gas transmission of 23.1 km length linking from the Tokyo Bay side to the opposite side of the circle. Main feature of this line is that the pipes of 610mm outside diameter, 7MPa MAOP and of Grade 552 (X80) equivalent material is to be installed within a tunneling shield all along the route to avoid unnecessary negotiation with road authorities and adjacent inhabitants. The 2m diameter tunnel will be excavated 40m under ground surface in average, 60m in the deepest. The construction started last autumn and will not be completed until the year 2009. This paper refers to be design concept and outline of the narrow and long tunnelling and piping techniques utilized to reduce the construction costs.