Publication Details

This article was originally published as Indraratna, B, Rujikiatkamjorn C and Sathananthan, I, Radial consolidation of clay using compressibility indices and varying horizontal permeability, Canadian Geotechinical Journal, 42, 2005, 1330-1341. Copyright National Research Council Canada. Original journal available here.


A system of vertical drains with surcharge load to accelerate consolidation by shortening the drainage path is one of the most popular methods of soft ground improvement. The conventional radial consolidation theory (including smear and well resistance) have been commonly employed to predict the behaviour of vertical drains in soft clay. Its mathematical formulation is based on the small strain theory, and for a given stress range, a constant volume compressibility (mv) and a constant coefficient of lateral permeability (kh) are assumed. However, the value of mv varies along the consolidation curve over a wide range of applied pressure (Dp). In the same manner, kh also changes with the void ratio (e). In this paper, the writers have replaced mv with the compressibility indices (Cc and Cr), which define the slopes of the e-logs' relationship. Moreover, the variation of horizontal permeability coefficient (kh) with void ratio (e) during consolidation is represented by the e-logkh relationship that has a slope of Ck. In contrast to the conventional analysis , the current study highlights the influence of the Cc/Ck (or Cr/Ck) ratio and the preloading increment ratio (Dp/si) on the consolidation process. The analytical predictions are compared with the experimental results using a large scale consolidation chamber, and these predictions show good agreement with the measured data. Finally, an embankment case history taken from Muar Plains, Malaysia is analysed based on the current solution, and compared with field measurements.

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