The soils engineer responsible for the adequacy of the design of embankments regularly finds himself confronted with the problem of constructing an embankment upon a foundation consisting of soft, potentially unstable soils. This thesis presents the method used to arrive at a successful solution to this problem and a discussion of the pore pressures developed in the foundation as the embankment was constructed. The determination of the shear strength parameters of the foundation materials for use in stability analyses and the type of stability analysis used are discussed. The use of effective shear strength parameters in the stability analyses required that the excess pore pressures developed in the foundation as the embankment was constructed be measured and 10 piezometers were installed in the foundation to provide the necessary pore pressure data. A comparison between the measured excess pore pressures and the excess pore pressures that a theoretical stress distribution indicated should have developed under the embankment load is included. Differences between the measured and theoretical pore pressures are noted particularly at the toe of the embankment slope. Stability analyses using the theoretical pore pressures gave higher safety factors than those obtained from analyses when compared with using the measured pore pressures. The only practical method of determining excess pore pressures caused by an applied load was concluded to be by instrumentation. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (p. [188]-195).

Thesis (M.C.E.)--University of Delaware, 2007. / Principal faculty advisor: Dov Leshchinsky, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

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. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Photocopy of typescript. / Digitized by Kansas State University Libraries

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A testing apparatus was developed for the determination of the change in permeability of coarse porous media subjected to a decrease in porosity . literature survey was conducted to establish the design criteria for the flow and loading tests. The mthemaUcal model describing flow through course porous media was further developed on a theoretical basis by postulating the layered medium model. Ihis model is a means by which the variability of the particle sizes in the medium is taken into account. The design, construction and operation of the testing apparatus is des:rvx-d. The specimen tested was laded up uo 3,45 MPa; consequently ' the Fbrcheimer aquation in the form of K , Ci/R + Cg was found to yield repeatable values for tiic turbulent friction factor C2, thus providing a means of predicting the change in permeability if the change in porosity and effective particle diameter are known.