North East Link Project, Melbourne, Australia Lower Plenty Road Interchange Diaphragm Wall Works-Video

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Video Summary

The presentation covered diaphragm-wall construction for Melbourne’s North East Link, a major motorway and tunnel project. A joint venture installed 471 panels, up to 43 metres deep, using four hydromills, with approximately 35,000 tonnes of reinforcement and 80,000 cubic metres of concrete. The walls form a cut-and-cover interchange box designed for top-down construction.<br /><br />The team faced difficult ground conditions, including strong siltstone, highly fractured rock, steeply dipping faults, and high groundwater. Several trenches collapsed, particularly after support slurry was replaced with lighter casting slurry. Investigations linked the failures to rock wedges, large panels, long excavation times, fluid-level changes, and groundwater. The response included shortening panels, strengthening slurry controls, and anchoring and grouting collapsed zones. Re-excavation also required careful treatment of bentonite contaminated by concrete.<br /><br />One further collapse resulted from using the wrong polymer, which deflocculated the slurry during casting. The speaker also discussed reinforcement congestion, concrete placement, and crosshole sonic logging results. Shorter panels severely affected productivity.

Keywords

diaphragm wall construction

North East Link

slurry trench collapse

groundwater

bentonite slurry

cut-and-cover tunnel