Design of reinforced embankments on soft clay deposits considering the viscosity of both foundation and reinforcement

The combined effects of the viscoplastic nature of foundation soil and viscoelastic behaviour of geosynthetic reinforcement (polyester, polypropylene and polyethylene) are investigated. A new method for defining the critical stage, with respect to embankment stability, and the operational field strain rate for use in assessing the undrained shear strength of rate-sensitive foundation soils similar to those examined is proposed. The effect of construction rate on the reinforcement stiffness at the critical stage is examined. The study shows that the selection of a design stiffness using the data obtained from a creep test provided reasonable and conservative results. The effects of the undrained shear strength profile, reinforcement stiffness and soil viscosity on embankment performance under working stress conditions are explored and a new limit equilibrium based design procedure is proposed. Finite Element analyses are used to examine the potential effectiveness of the proposed simplified design procedure.