Microtunnelling adjacent the southern portal of the North East Link project

Abstract

Abstracts should be limited to 250 words maximum. As part of the North East Link Project’s Early Works package, relocation of the Yarra East Main Sewer (YEMS) was required. This package of work focused on the Melbourne Water (MW) and Yarra Valley Water (YVW) sewer relocation for the YEMS. The relocation of the main sewer and associated branch sewers has been carried out predominantly using trenchless techniques, including the use of multiple AVN slurry micro tunnelling machines, Earth Pressure Balance (EPB) micro tunnelling machines, hand jacking pipe installation and Vermeer axis guided boring systems. During the design, significant challenges arose with respect to changes to alignment and shaft locations. Adjustments to jacking force calculations were also completed during construction to optimize the performance-based design approach to tunnelling. This included reviewing the design jacking force calculations and recalibration against actual forces measured while tunnelling, which allowed for a reduction in the number of total inter-jack stations. Temporary shafts faced many constraints due to amenity and public disruption, buried services, variable subsurface conditions and surface flooding risks. Selecting suitable trenchless methodologies for the task meant that the impact on local businesses, sports facilities, schools and other stakeholders could be kept to a minimum. Solving technical challenges on the job while working closely together with the contractors meant that new knowledge could be gathered regarding the behavior of micro tunnel boring machines in various ground conditions. These learnings are now available to be carried forward and used for future tunnelling projects in the eastern suburbs of Melbourne. 1 No-Dig Down Under 2023 [Microtunnelling adjacent the southern portal of the North East Link project] [Barnabas Ilko/Trevor O’Shannessy]

Techniques