Stability Analysis of Geosynthetic-Reinforced Shallow Foundations with a Lower-Bound FELA Approach Adopting the Nonassociated Plastic Flow Rule

Abstract

Finite-element limit analysis (FELA) is an effective numerical method to evaluate the stability of reinforced geostructures. Such an analysis has been commonly performed in the literature by assuming the earthen material to follow the well-defined associated plastic flow rule. In this study, the effect of adopting the nonassociated plastic flow rule on the ultimate bearing capacity of eccentrically-obliquely loaded shallow footings placed over geosynthetic-reinforced granular soil is rigorously examined through a comprehensive set of lower-bound FELA simulations along with second-order cone programming. The nonassociativity of the plastic flow rule is incorporated into the formulation of the Mohr–Coulomb yield criterion by considering a wide range of dilation angles (ψ) varying between 0 and the soil internal friction angle (φ). Unlike the previous FELA studies, both pull-out (sliding) and tensile (structural) modes of geosynthetic failure are taken into account. Accordingly, the impact of considering the nonassociated flow rule for the sand deposit on the bearing capacity ratio, failure envelopes, and the failure mechanism of overlying shallow foundation is investigated and discussed. The results show that failing to consider the significant influence of nonassociativity in the FELA simulations leads to overestimations of the tensile forces mobilized in the reinforcement layer as well as the ultimate bearing capacity of the overlying shallow foundation, thus yielding nonconservative and insecure designs.