Ground Improvement using Pre-loading with Prefabricated Vertical Drains

Ashutosh Sutra Dhar, Abu Siddique, Syed Fakrul Ameen

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A container yard was constructed for handling of loaded containers at Chittagong Sea Port in Bangladesh covering an area of 60700 m2 over a sub-soil that included a layer of soft stratum of clayey silt/silty clay at the depths of 0 to 3.5 m below grade. Thicknesses of the soft stratum varied from 3 m to 7 m. Ground improvement using pre-loading with prefabricated vertical drains was undertaken to pre-consolidate the compressible sub-soils, which was followed by field monitoring. It is revealed that the classical theories can effectively be used in calculating the consolidation settlement and the time for consolidation. Predicted settlements and the consolidation time matched reasonably with the measured values. To account for the smear effects, the coefficient of consolidation and the coefficient of permeability were taken as those for vertical flow. Predictions with the smear diameter as two times the equivalent drain diameter provided an upper bound of the consolidation time while prediction without consideration for smear effects provided a lower bound of the consolidation time for the container yard project.


Ground improvement, consolidation, vertical drain, compressible soil, container yard


Dhar, A. S., Siddique, A., Ameen, S. F. (2011). Ground Improvement using Pre-loading with Prefabricated Vertical Drains, Vol. 2, Issue 2, p.86-104. doi: 10.4417/IJGCH-02-02-01


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