Jacked Pipe Provides Roof for Underground Construction in Busy Urban Area

Abstract

Construction of a major underground station for the metro in Antwerp, Belgium was done in a busy downtown area employing a method that virtually eliminated ground subsidence. The method consisted of jacking 1.3-m asbestos cement pipes horizontally into the earth, excavating from inside, then adding reinforcing steel and concrete. This created a series of reinforced concrete beams covering more than 4,500 m² that served to roof over subsequent construction operations that took place underneath. Two lateral tunnels were excavated under the extremities of the beams to build support walls. Excavation of the remaining area under the pipe-beam roof followed. Construction operations in the large underground site included installation of slurry wall foundations and slabs for the 5-story station structure. The pipe was jacked as close as 0.6 m to street level without affecting surface activities, business or traffic, and with negligible ground subsidence.