NEW INSIGHT INTO THE COMPRESSIBILITY AND STRUCTURED NATURE OF COODE ISLAND SILT

As part of the Regional Rail Link (RRL) project in Melbourne, Australia, a number of geosynthetic reinforced (GR) embankments with ground improvement were constructed where the rail alignment passes over the Coode Island Silt (CIS), a well-known soft soil encountered around inner Melbourne. To better understand the behaviour and performance of the load transfer platform (LTP) at the base of these embankments, a field case study has been undertaken which has seen an extensive array of instrumentation installed within the North Dynon embankment. This paper presents and describes a significant amount of field and laboratory data gathered as part of the geotechnical site characterisation of the instrumented areas. Based on this data a description of the compressibility and permeability of the CIS is presented and insight into the structured nature of the CIS is described. In addition, it is shown that a far better characterisation of soft soil behaviour can be gained through the use of more sophisticated oedometer testing techniques.