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UBC Theses and Dissertations

Prediction of embankment performance using in-situ tests Leclair, Donna Gail


In-situ piezocone, flat dilatometer, and screw plate tests were carried out adjacent to the site of several large earth embankments, founded on a deep deposit of compressible soil. Settlement records since construction were available for two of the embankments. Geotechnical parameters were not back analyzed from the case record, rather, embankment performance was predicted on the basis of parameters interpreted from the in-situ tests alone. Consolidation characteristics were interpreted from the measurement of dissipation of excess pore pressures using the piezocone and dilatometer. Both devices provided complementary results in terms of an appropriate coefficient of consolidation. The excellent stratigraphic profile furnished by the piezocone (CPTU) tests proved to be a most valuable feature. The stratigraphic detail provided by the CPTU tests performed across the site identified continuous, free (framing soil layers which would generally be missed in a conventional geotechnical investigation using a drilled borehole with discrete sampling. The identification of these layers was of paramount importance in the prediction of settlement rate. A one-dimensional analysis formed the basis for the settlement predictions, and was found to be satisfactory. Settlement magnitudes were predicted within 10% of the observed measurements, parallelling the observed rate of settlement throughout the embankment construction period in the early 1970's and to the present date. Key words: settlement, deltaic soils, embankment, in-situ testing, piezocone, flat dilatometer, screw plate, coefficient of consolidation, compressibility, pore pressure dissipation.

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