Design challenges of the cross city tunnel

The Cross City Tunnel Project provides Sydney, Australia with almost 6 km of new underground road network in the heart of the Central Business District. The project aims to provide Sydney commuters with up to a 20 min time saving in cross city travel, achieved with the bypassing of some 18 sets of traffic lights. The project alignment is complex, involving six separate tunnels, three underground y-junctions, six crossover slabs and a network of construction and egress cross passages and shafts. Beneath William Street, Sydney, all six tunnels run parallel for some 200 m at different levels below the existing surface. The route runs adjacent to or below many major buildings, existing and future rail tunnels, existing viaducts, road tunnels and many major services. The Cross City Tunnel is being constructed by Baulderstone Hornibrook Bilfinger Berger JV (BHBB) on behalf of the Cross City Motorway (CCM) consortium. CW-DC Pty Ltd (a fully owned subsidiary of Connell Wagner Pty Ltd) is the principal civil designer for BHBB. The construction phase of the project commenced in early 2003 and is programmed to finish in December 2005. The tunnel alignment has been achieved with strong dependence on 3D road design packages. Alignment constraints include land acquisition and proximity to existing tunnels, basements and other infrastructure as well as maintaining acceptable separation between adjacent tunnels in the project. The alignment incorporates all existing road networks into the new scheme. The geotechnical difficulties to overcome include the high horizontal stress field within the Sydney basin, numerous fault and shear zones and palaeochannels that all six tunnels pass. The design includes the incorporation of flat roof and conventional arched hard rock tunnelling methods. The challenges include design of large span tunnels in close proximity to existing tunnels and large building basements, incorporation of a by-pass ventilation system, design of reinforced concrete cross over slabs within the tunnel for future rail and existing road tunnels and detailed settlement predictions for the existing buildings, tunnels, structures and services. The latter includes a detailed assessment on the impact to over 200 buildings along the alignment, many in excess of 20 storeys. (A). "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.


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  • Accession Number: 01011629
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 19 2005 3:22PM