| Abstrakt: |
This paper provides an overview on the construction methodology, design features and progress to date for cross passage works as part of the West Gate Tunnel Project (WGTP) in Melbourne, Australia. A review of the geological conditions and ground treatment is also provided. Traditionally, cross passages are mined in stages using mechanical excavation followed by the installation of a temporary sprayed concrete lining likely combined with other passive and active support solutions. Casting of the permanent insitu lining typically follows once excavation is complete. Whilst a small number of cross passages on the WGTP followed this approach, an innovative box jacked methodology was used for the majority of the cross passages. A rectangular Box Jacked Machine, consisting of several elements including a shield, tail skin and reaction frame was assembled for each cross passage and 'jacked' under atmospheric conditions. Rectangular segments are installed sequentially allowing for completion of excavation and installation of the permanent lining consecutively. Whilst traditionally mined cross passages will always have their place in cross passage construction, the WGTP has shown that the use of the box jacked method is a viable methodology so long as space and geological conditions are met. At least half the tunnel was utilised on both road deck and invert level for the Box Jacked Machine, which maintained access at road deck and invert levels for other work fronts to continue uninterrupted. The jacked box method has been found to be a favourable method in Extremely to Slightly Weathered Older Volcanics where excavation cycles are on average 10-12 days. Deformation monitoring is found to be stable for cross passages completed to date following completion of jacking operations and permanent works. [ABSTRACT FROM AUTHOR] |
