Characterising soft alluvial deposits in Launceston

Holocene alluvial deposits, underlying many parts of the northern suburbs of Launceston, Tasmania, have posed significant geotechnical risks to the operation, design and construction of engineering structures in those areas. The objective of this paper is to present a characterisation of these alluvial deposits from mainly piezocone and normal electric cone penetration testing. These tests were performed at two near shore sites of the North Esk River and its confluence with the Tamar River, as well as another site in Invermay north of Launceston’s CBD. These deposits are known to be predominantly soft to very soft, but are poorly characterised in geotechnical terms, with the information in hand being largely in the form of geological and geomorphological descriptions, including observations by local drillers and pile driving operation staff. The geotechnical characterisation information presented in this paper will be useful for the design and construction of engineering works where the investigated deposits are present.