Assessment Of Reliability Of The Hydrometer By Examination Of Sediment

Proceedings of the first Southern African Geotechnical Conference - Jacobsz (Ed.) © 2016 Taylor & Francis Group, London, ISBN 978-1-138-02971-2A fundamental aspect of the characterization of any soil is the assessment of its particle size distribution. While this is relatively easy for the coarse fraction it remains problematic for soil fines particularly for the fraction less than 2μm. Hydrometer analysis has been the standard tool for fines assessment for many years but there may be serious shortcomings. Nettleship et al. (1997), Savage (2007), Rodrigues et al. (2011) and many others have pointed to a number of problems facing the hydrometer. Some of the questions have been addressed by laser scattering techniques e.g. Eshel et al. (2004), but others, including completeness of dispersion and the amount of clay carried down with coarser fractions remain problematic. This investigation assesses some aspects of the reliability of the hydrometer by isolating and testing the sand and silt fractions after settlement. Microscopic examination is used to compare the composition of sediment layers with that expected according to hydrometer theory