Modelling self-weight consolidation in Holocene sediments

Self-weight consolidation has been analysed using a variable-layer thickness, iterative, forward-modelling method. Results expressed in terms of the decompaction factor show that the true sedimentation ratio exceeds the raw sedimentation rates, or estimates from backward-modelling, by a factor of two or more. Robust estimates of the decompaction factor may be obtained from the total sequence thickness with minimal assumptions about the physical properties of the sediments. The results apply both to marine sediments from Hong Kong and the Forth Estuary, Scotland. Modelling of the pore pressure decay suggests that during active deposition an excess pressure is maintained within the sediment column preserving an open microstructure. This result may be one explanation for the high level of geotechnical structure often found in such sediments. For the sediments studied there is a unique, linear relationship between the compression index and the void ratio at unity vertical effective stress.