Behaviour of reinforced embankments on soft rate-sensitive soils

Abstract

The behaviour of reinforced embankments constructed over rate-sensitive soft foundation soils is studied. Factors such as the viscoplastic properties and hydraulic conductivity of the soil, reinforcement stiffness and construction rate are examined. The time-dependent responses of excess pore pressures, reinforcement strains and foundation deformations are investigated. The short-term embankment stability is of particular interest. The construction of reinforced embankments to the height determined based on a limit equilibrium design is simulated to examine the assumptions made in the conventional undrained analysis. It is shown that creep and stress-relaxation of viscoplastic soils after the end of embankment construction may be significant for rate-sensitive soils. The embankment stability is shown to be critical during creep and stress-relaxation of foundation soils after construction. The undrained shear strength measured in laboratory triaxial tests using currently recommended strain rates without an appropriate correction may lead to unsafe design for rate-sensitive soils. For such soils, the increase in reinforcement strain shortly after the completion of construction can be higher than that developed during the construction. Excess pore pressures increase after construction owing to the viscoplastic behaviour of the foundation soil. Reinforcement is shown to have the potential to both increase stability and decrease long-term creep deformations.