A spreadsheet based stability calculation for geosynthetic reinforced column-supported embankments

Design procedures for Geosynthetic Reinforced Column-Supported (GRCS) embankments should consider both internal stability arising from failure of single columns and external stability arising from failure of the embankment as a whole unit. A number of possible failure mechanisms for external stability due to slip circle failure and sliding failure of group of columns as a single unit are discussed in the literature. However, internal stability issues due to failure of individual columns have not been received much attention. Therefore, an indepth understanding of individual column failure and subsequent progressive failure of embankments is an important topic, which needs attention when investigating the stability of GRCS embankments. In this paper, two-dimensional finite element modelling incorporating strain-softening behaviour of cement mixed soils has been used to identify the individual column failure of GRCS embankments at the Ultimate Limit State. Results show that the bending failure of individual columns progressively leads to develop a failure plane within the column improved ground causing internal stability issues. For the identified failure mode, an analytical equation is proposed to calculate the factor of safety against shear failure due to progressive bending failure of columns based on the Coulomb's wedge theory. Since the proposed approach can be conveniently implemented in an EXCEL spreadsheet program, it is useful for practicing geotechnical engineers.