Vane shear strength of dewatered sludge from Hong Kong

The vane shear strength and total solids content of dewatered sludge from H ong Kong were determined in order to evaluate their geotechnical suitabilit y for disposal in landfills. The results obtained indicate that (i) the tot al solids and vane shear strength of dewatered sludge from different treatm ent plants varied considerably depending on the type of sludge and dewateri ng method; and, (ii) percent total solids alone is not sufficient to guaran tee geotechnical stability in terms of vane shear strength. The critical st ate model for soils provided a good fit for the characteristic relationship between vane shear strength and total solids, which can be used to estimat e vane shear strength from total solids only. No relationship between volat ile solids and vane shear strength was found. The results of the laboratory vane shear test correlated well with those obtained by a pocket shearmeter indicating the usefulness of this method for rapid determination of vane s hear strength on site. Some factors that influence vane shear strength were briefly evaluated. Implications of the results for sludge management with special emphasis on dewatering and landfilling were discussed.