ABSTRACT
A rapid Light Rail Transit (LRT) system was constructed in the City of Edmonton, Canada to connect the downtown area to the northeast suburbs in the 1970s and later to the south side. The stretch of the LRT passing through the heavily developed downtown area was constructed underground. The underground stations were constructed using the cut-and-cover technique and were connected with two twin circular tunnels about 6.2 m in diameter, and spaced at 11 m centerline to centerline. The tunnels were constructed using a Lovat open face Tunnel Boring Machine (TBM) with the west-bound tunnel, referred to herein as the first tunnel, constructed first followed by the east-bound tunnel, referred to as the second tunnel.The primary lining system consisted of steel ribs spaced at 1.22 to 1.53 m center to centre, and 100 × 150 mm lagging placed between the webs of successive ribs. The secondary lining consisted of cast-in-place reinforced concrete. Detailed information on the lining activation
method can be found elsewhere, e.g. Eisenstein & Thomson (1978) and El-Nahhas (1980).
