Foundation problems in dredge fill soils overlying soft organic layer

摘要

Most parts of the Dhaka city having competent subsoil for building construction are already exhausted.rnAs such new areas are being reclaimed using dredged fill soils. It is found that top filling layer (averagernthickness: 3.5 m) is non-plastic fine sand (mean grain size: 0.14～0.19 mm) which is vulnerable to liquefaction.rnA very soft organic clay (organic content: 4.4～29.4%) layer (average thickness: 4.5 m) exists beneathrnthis filling layer. Liquid limit and plasticity index of the organic soil vary from 42 to 190% and 17 to 62%, respectively.rnInitial void ratio and compression index of the organic clay vary from 0.87 to 3.70 and 0.33 to 1.25,rnrespectively. No correlation could be established between the strength, compressibility and index properties. Itrnis estimated that the soft organic layer will undergo a very large settlement (447 to 1734 mm) due to the surchargernfrom the top filling layer. Negative skin friction is likely to be a major design consideration for deeprnfoundation in these areas.