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This package of works involved the removal of three level crossings (two at St Albans and one at Heatherdale Rd, Mitcham) using rail under road methodology in two very different types of ground conditions.

At St Albans, where ground conditions are volcanics (basalt floaters in matrix of highly plastic clays), Geotech installed over 7,000 soil nails totalling approx. 36,000 lin m of drilling. The scope also extended to supply & installation of 30 permanent ground anchors and approximately 15,000 square metres of shotcrete (fibrecrete) to the exposed cuts. Geotech utilised an excavator mounted shotcrete unit to allow safe application of the fibrecrete at heights of six metres. This enabled fast-tracking of the soil nailing and excavation process to the bottom of the cut, ensuring earliest possible access for the following trades. Around one third of the soil nailing scope was completed in a single four-week, 24 hour a day full occupation of the rail corridor.

At Heatherdale Rd, Mitcham, where ground conditions are more predictable Silurian clays over siltstone, Geotech installed around 2,000 soil nails with a total 9,000 lin m of drilling. Associated works included the application of shotcrete (fibrecrete) facing to the batters and some temporary steel sheet piling. Significant portions of the works were undertaken while trains were running. Drilling works were completed using a purpose-built excavator mounted drill rig and shortened mast drill rigs to complete as much of the scope as possible outside the full occupation of rail corridor.

Both sites featured comprehensive sacrificial and production testing of soil nails to VicRoads’ specifications.

Disciplines covered

• Soil Nails
• Permanent Ground Anchors
• Shotcreting
• Steel Sheet Piling
• Soil Nails Testing