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 performed on sludge with various initial water contents of 0.13-1.48 times the liquid limit. It is observed that the sludge is organic high liquid limit silt, whose e-logσv‘ compression curves are inverse "S" shape due to organic floc structure of sludge potentially. When the effective vertical stress σv‘ > 100 kPa, a clear gap of compression curves of various initial water contents still exists, different from the viewpoint of Burland (1990) that compression curves tend to be consistent. Burland's concept of intrinsic compression line is adopted for correlating compression curves of sludge well, and an intrinsic compression line of the sludge is derived. The intrinsic compression line of sludge is below that of Hong (2010) and Burland (1990) when σv‘ < 100 kPa, due to the difference in initial water contents. A generalized void index is tentatively proposed by introducing generalized 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.