2008 Volume 48 Issue 4 Pages 547-561
The objective of this study is to empirically clarify the scale effect in long-term consolidation behavior. Frictional pressure loss arising at the interface between the consolidation ring and the specimen must be considered, when the specimen thickness increases. This study uses a special oedometer that can evaluate the quantity of the frictional pressure loss. Incremental loading oedometer tests are carried out in order to evaluate the frictional pressure loss in the normal oedometer test using a specimen with a height of 20 mm. The frictional pressure loss ratio generally exceeds 0.2 when the consolidation pressure is less than approximately 300 kPa, rather than the overconsolidation range. Consequently, a series of inter-connected type consolidation tests, in which the frictional pressure loss can be minimized by limiting the thickness of each specimen element, are carried out in order to investigate the scale effect of the specimen thickness in the range of 20-200 mm. The end of primary consolidation (EOP) can be clearly identified in the excess pore pressure dissipation. The law of squared H is essentially valid for the pore water pressure dissipation. However, the EOP becomes unclear in the strains when the specimen thickness decreases. The compressive strain at the EOP stays constant or slightly increases with the specimen thickness.