Remediation of flood damage on the Toowoomba Range Railway, Queensland, Australia

摘要

The Toowoomba Range Railway is located on the eastern side of the Great Dividing Range approximately 110 km west of Brisbane, Australia and was originally constructed in 1867. This locality in the Upper Lockyer Valley is characterised by steep terrain with surface elevations reaching approximately 600 m above sea level. Following the flash flood events of January 2011, the railway sustained significant damage including washouts of embankments and culverts, failure of upslope cuttings, destruction of a bridge and damage to a gas pipeline. A geotechnical assessment was undertaken along a 25 km length of railway and over 100 failure features were identified as having an impact on operation of the railway. Twenty failure features were considered significant in nature and required engineering input during the remedial design and/or reconstruction phase. Initial estimates by Queensland Rail predicted a 3 to 6 month repair program. Detailed topographic information for selected sites was obtained by an aerial photogrammetric survey from a manned helicopter using the 3DM Analyst digital photogrammetry system. Reconstruction of the flood-damaged earthworks and culverts utilised robust solutions that could be implemented quickly and this typically comprised excavation of failed material and replacement with rockfill, installation of large steel culverts, and at one location the use of pre-cast concrete L-section panels to retain a steep rockfill embankment. A six week program of investigation, pile design and construction was implemented for replacement of the damaged bridge. The first train resumed service on 28th March 2011, about two and a half months after the flood, which was well ahead of schedule.