Limit equilibrium analyses of two-tiered geosynthetic-reinforced soil wall models in a geotechnical centrifuge

The FHWA guidelines limit the use of limit equilibrium (LE) method for designing reinforced slopes (face inclinations less than 70°); however, this limitation is somewhat arbitrary and there is no reason why LE method could not be theoretically applicable in the design of reinforced walls and those with complex geometry such as multi-tiered walls. This study therefore evaluated the use of LE for predicting failure in centrifuge two-tiered geosynthetic-reinforced soil (GRS) wall models with varying offset distances, D. The LE analysis results revealed good agreement between LE and centrifuge models in locating failure surfaces. This study also examined the effect of offset distance on the confined (or in-soil) ultimate tensile strength of reinforcement, T_ult. The confined T_ult was back-calculated from the LE analyses at the failure of centrifuge wall models (i.e., FS=1.0). The analytical results showed that offset distance correlated negatively with the effective overburden pressure on reinforcement and the resulting confined T_ult. In addition, this study evaluated the effect of offset distance on the normalized reinforcement tension summation coefficient, K_T, an equivalent earth pressure coefficient derived from the confined T_ult. The analysis results indicated that single and independent wall modelsyielded a single consistent K_T value, while in the compound wall models the K_T value decrease as the offset distance D increases. The presented experimental results and discussions improve the understanding of limit equilibrium analysis of multi-tiered reinforced walls.