Effects of initial water content on compression behaviour of municipal sewage sludge

Abstract

To investigate effects of initial water content on compression behaviour of municipal sewage sludge and clarify its intrinsic compression characteristics. Oedometer tests were conducted on sludge with various initial water content of 0·13–1·48 times the liquid limit. It is observed that the sludge is organic high liquid limit silt, whose e–log σ′v compression curves are inverse ‘S’ shape due to organic floc structure of sludge potentially. When the effective vertical stress σ′v > 100 kPa, a clear gap of compression curves of various initial water content still exists, different from Burland's viewpoint that compression curves tend to be consistent. Burland's concept of intrinsic compression line (ICL) is adopted for correlating compression curves of sludge well, and an ICL of the sludge is derived. The ICL of sludge is below ones reported by Hong and Burland when σ′v < 100 kPa, due to the difference in initial water content. A generalised void index is tentatively proposed by introducing generalised intrinsic parameters e*y1 and e*y2, which may be related to the loading history of the soil and the maximum load that the soil may bear in future engineering, respectively.