Material re-use and in-situ stabilisation of sand and clay mixtures for rail formation in South-East Melbourne

As part of the Level Crossing Removal Project in Victoria, Australia, the Southern Program Alliance (SPA) is removing numerous level crossings along the Frankston line in South-East Melbourne. At Parkdale, two level crossings have been removed and replaced with a rail viaduct (rail over road) solution.

The surficial geology of the Parkdale site consists of aeolian sands underlain by sand and clay of the Sandringham Sandstone formation. An important component of rail viaduct solutions is the earthworks associated with backfilling of approach embankments to the viaduct, and the formation earthworks associated with tying into the existing rail network. The SPA implemented an approach to re-use material from large excavations as select backfill for the approach embankments, and proposed lime and cement stabilisation of in-situ materials for rail formation, to attain time, cost and sustainability benefits to the project. This paper summarises key investigation and design considerations of soil compaction and strength behaviour identified in laboratory testing, along with anecdotal construction commentary, to promote the benefits and discuss the challenges of material re-use and stabilisation in large rail infrastructure projects.