Design And Construction Of Cantilever Retaining Wall Near Railway Line: (Case Study – 359 Illawarra Road, Marrickville NSW)

The proposed “Revolution Apartments” is located at the corner of Illawarra Road and Byrnes Street, Marrickville NSW and replaces the Marrickville RSL Club. The development comprises seven level building, partly underlain by a two level basement car park. The Marrickville Railway Station sits on the southern boundary. The nearest track of the railway line was set back by about 3m to the site boundary. An existing Sydney Water “Storm-water Underground Channel” was running through the proposed building. The development required the decommissioning of the existing Sydney Water culvert and the construction of a new concrete lined culvert between the proposed building and the south boundary. A permanent cantilever wall is proposed because the anchor system is not permitted into the railway Corridor. The maximum excavation depth is about 3.5m. As a result of the excavation works, ground movement is expected. The challenge of this project is that, the proposed retaining wall shall meet the track settlement limits in accordance with RailCorp SPC 207 (Track Monitoring Requirements for Undertrack Excavation, 2013). It was required to limit any movement to “Alarm Level 1” as per the Railcorp specification, which is defined by any detected movement, both vertical and horizontal, to be less than 15mm. Frankipile submitted a design and construct proposal comprising a cantilever contiguous pile wall along the boundary to the railway Corridor. In order to monitor the deflection of the wall during the excavation works, three inclinometers were installed at the most critical section of the contiguous shoring wall adjacent to the railway track boundary. The railway lines were monitored independently by surveyor engaged by Railcorp at some 200 points and the presentation will review these results in the light of the inclinometer monitoring results. Computer software WALLAP and PLAXIS were used in design to estimate the wall deflection and ground movements. The analysis results are compared with the monitoring results and soil parameter studies are also carried out.