Undrained Settlement of Plastic and Organic Clays

by Roger Foott, (M.ASCE), Program Mgr.; Soils and Foundation Engrg., Dames and Moore, Burlington, Mass.,
Charles C. Ladd, (F.ASCE), Prof.; Dept. of Civ. Engrg., Massachusetts Inst. of Tech., Cambridge, Mass.,

Serial Information: Journal of the Geotechnical Engineering Division, 1981, Vol. 107, Issue 8, Pg. 1079-1094

Document Type: Journal Paper


For most foundation loading situations, initial settlements due to undrained shear deformations are small. The common practice of computing consolidation settlements using the conventional 1-dimensional model therefore generally yields total settlement estimates of sufficient accuracy for design purposes. Initial settlements can become a predominant design consideration with highly plastic or organic foundation soils, or both, however—especially when loaded to low stability factors of safety, as illustrated by three case histories. Moreover, with slow field rates of consolidation, the occurrence of large initial settlements may also be followed by excessive undrained creep deformations. A semi-empirical method is presented for predicting the magnitude of initial settlement and the likelihood of excessive creep movements. Ways of reducing detrimental undrained shear deformations in design practice are explored.

Subject Headings: Soil settlement | Foundation settlement | Shear deformation | Load factors | Foundation design | Plastics | Clays | Model accuracy

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