Short-term design of geosynthetic-reinforced embankments on soft foundation soils

The stability of an embankment on soft foundation soil is most critical during the construction period, because of the relatively low permeability of the soft foundation. Since the stability increases as the foundation consolidates, related design is controlled by short-term constraints. Geosynthetics for basal reinforcement enhance the stability of an embankment over soft soil by preventing lateral sliding of the fill, extrusion of the foundation and rotational failure. The stabilizing force developed by the reinforcement is generated by shear stresses mobilized along both the interface surfaces of the reinforcement, with the foundation soil and the embankment fill respectively. In fact, the reinforcement has the double function of carrying the outward shear stresses transmitted by the embankment fill and of providing inward shear stresses to restrain the foundation soil from lateral squeezing-out. For each of the limit states mentioned above, the associated reinforcement strength and bond length should be checked to ensure that the limit state tensile load can be generated in the reinforcement. Starting from considerations proposed by the British Standard 8006:2010, this paper focuses on lateral sliding and foundation extrusion limit states by presenting a design method to evaluate the reinforcement strength and bond length required to provide the maximum improvement for an embankment on soft soil.