Stability of an embankment on soft clay

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.