MTBM VS Sheet pile, battle for the ages

Abstract

Thornlie - Cockburn Link (TCL) project, consists of new railway line between the Armadale and Mandurah lines via the Thornlie and Cockburn Stations. The track extension from Thornlie to Cockburn is approximately 14.50 km consisting of narrow gauge 1067mm ballasted (at grade) and slab track (in tunnels and dives) permanent way. As a part of the TCL project, the BP Kewdale White Oil Line (a BP asset known as KWOL) required relocation to make way for the construction for the remainder of the project. A component of this relocation required a microtunnel (or Thrust Bore) crossing below the Public Transport Authority's (PTA) of WA Thornlie passenger railway line and the Arc Infrastructure freight railway line – between Thornlie Station and Canning River. In December 2021, during construction of the microtunnel, the MTBM (Micro Tunnel Boring Machine) hit an unknown obstruction ceasing tunnelling operations. Upon investigation this obstruction was found to be a temporary works (sheet pile) used to retain the Arc freight rail during construction of the PTA Thornlie Line railway bridge crossing Canning River in 2004. As there were no suitable re-design options available, and after multiple recovery options were explored, it was decided in PTA’s Disruption Access Meeting team that the best available opportunity to recovery the MTBM was to take possession of the rail and recover the MTBM during the Easter 2022 period (14 April 2022 to 19 April 2022). This paper is a case study about this issue encountered and recovery worked carried out.

Techniques