Geotechnical Testing Journal, Vol. 28, No. 6 Paper ID GTJ11887 Available online at: www.astm.org TECHNICAL NOTE Anthony D. Stickland, 1 Peter J. Scales, 2 and John R. Styles 3 Comparison of Geotechnical Engineering Consolidation and Physical Science Filtration Testing Techniques for Soils and Suspensions ABSTRACT: Traditionally, there have been two approaches to the modelling and prediction of the extent and rate of dewatering of particulate networks: consolidation theory and filtration theory, developed by geotechnical engineers and physical scientists, respectively. The physical situations and governing equations for Terzaghi’s consolidation model (Terzaghi and Peck 1967) and Landman and White’s filtration model (Landman and White 1997) are essentially the same. However, their methods of determining the relative dewatering parameters differ. The consolidation method matches experimental data from oedometer testing to the theoretical predictions of the model in order to determine the coefficient of consolidation, c v . The filtration method determines a solids diffusivity coefficient, D, based upon the experimental data from a filtration rig, which is then used in modelling to make predictions. This work aims to highlight the similarities between the two approaches, initially by demonstrating the theoretical relationship between the two parameters, c v and D, and then through experimental determination. The material characteristics of a kaolin sample undergoing one-dimensional (zero lateral strain) compression are determined using both oedometer and filtration testing and equated using the devel- oped theoretical relationship. The results indicate that the two testing methods are essentially the same, and that their relevant analysis tech- niques give similar outcomes. Consequently, geotechnical engineers can use filtration methods and physical scientists can use consolidation methods. KEYWORDS: Compressibility, coefficient of consolidation, consolidation testing, dewatering, filtration, oedometer, permeability, soils, solids diffusivity, suspension Nomenclature c v Terzaghi’s consolidation coefficient (m 2 /s) D(φ) solids diffusivity (m 2 /s) d average pore length (m) e void ratio e 0 initial void ratio h height of sample (m) k hydraulic conductivity (m/s) m v coefficient of volume compressibility (ms 2 /kg) P f excess pore pressure (N/m 2 ) P y (φ) compressive yield stress (N/m 2 ) P applied pressure (kPa) R(φ) hindered settling function (kg/m 3 s) T dimensionless filtration time t filtration time (s) t 50 time to 50 % consolidation (s) Received Jan. 31, 2003; accepted Apr. 5, 2005; published Nov. 2005. 1 Research Fellow, Particulate Fluids Processing Special Research Centre, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria, Australia, 3010. 2 Author for correspondence: Professor, Particulate Fluids Processing Special Research Centre, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria, Australia, 3010; Phone: 0061-3-83446480, Fax: 0061-3-83446233, E-mail: peterjs@unimelb.edu.au. 3 Senior Lecturer, Department of Civil and Environmental Engineering, The University of Melbourne, Victoria, Australia, 3010. t 90 time to 90 % consolidation (s) U degree of consolidation u f /u s fluid/solid velocities (m/s) V specific volume of filtrate (m 3 /m 2 ) β 2 inverse of slope of t versus V 2 , dV 2 /dt (m 2 /s) φ solids volume fraction φ 0 initial solids volume fraction φ ∞ final solids volume fraction γ f fluid weight (kg/m 2 s 2 ) σ ′ effective vertical stress (N/m 2 ) Introduction The dewatering and consolidation of saturated soils and floccu- lated suspensions are important operations for many industries. An understanding of the processes involved is invaluable when ana- lyzing any area where solid-liquid separation occurs, such as the settlement of structures, the stability of slopes, the design of pile foundations, the consolidation and reclamation of tailings dams, and the dewatering of suspensions. An ability to predict the dewa- tering behavior allows for better design and operation. For example, sewage sludges and mineral tailings require minimization of ma- terial volume for cost-effective disposal, while safe construction techniques require detailed knowledge of the degree of settlement that soils undergo. Considering saturated soils as highly concentrated suspensions or suspensions as high void ratio soils, the physical situations of Copyright © 2005 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 1 This standard is for EDUCATIONAL USE ONLY.