Analytical solutions to evaluate bending failure of column supported embankments

Design procedures for Geosynthetic Reinforced Column Supported (GRCS) embankments generally consider the sliding failure for external stability and the shear failure mode for internal stability. However, other failure modes such as collapse failure, slip circle failure, punching shear failure around column heads (overall or local), and bending failure of DCM columns are also significant for GRCS embankments. Although some design procedures have considered some of these failure modes and proposed design criteria to check against these failure modes, they are not currently used in practice due to uncertainties related to some assumptions used in developing these methods, unreliable results given by them and difficulty in finding some parameters. Still there are uncertainties in identifying the critical failure modes for these embankments at the ultimate limit state (ULS) conditions. In this paper, two-dimensional finite element modelling incorporating strain softening behavior of cement admixed soils is used to identify the failure modes of GRCS embankments at the ULS. Bending failure of columns with subsequent shear failure is found to be critical for internal stability of GRCS embankments. Consequently, analytical equations are derived to calculate the factor of safety against bending failure for improved ground considering driving and resisting moments.