TOP-DOWN ROAD TUNNEL BUILT FOR PERTH

This article reports progress on the construction of a 1.6km long road tunnel in Perth, Western Australia. It includes a route map. The tunnel is the first road tunnel to be built in Western Australia, and is part of a 6.5km new bypass to ease congestion in Perth's city centre, which is scheduled to open in June 2000 and will also include a new bridge across the Swan River. The tunnel was designed by the Maunsell Group. In September 1996, Baulderstone-Clough JV (BCJV) began construction, using a specified top-down method. The BCJV contract also includes laying the road surface, installing ventilation and drainage and pumping, construction of surface works, and extensive diversions of underground services. In addition, there is a 200m cut-and-cover tunnel to relocate railway tracks under the new road alignment. By February 1998, about 50% of the diaphragm wall was complete, and the concrete roof slab had been placed over about 40% of the route. Excavation of the core and integrated casting of the floor slab had advanced about 250m, and internal walls had begun. By early June, work remained on schedule, with 620m out of 1612m of the tunnel core excavated, about 570m out of 1630m of the concrete floor laid, over 400m out of 1630m of internal walls cast, diaphragm walling 72% complete, and 63% of the roof slab in place.