Limit equilibrium analyses of geosynthetic-reinforced two-tiered walls: Calibration from centrifuge tests

The use of limit equilibrium (LE) for predicting performance at failure in centrifuge two-tiered geosynthetic-reinforced soil (GRS) wall models was evaluated. The variables considered in the centrifuge testing program were offset distance, D, and reinforcement length. Parametric studies were first performed to evaluate the effects of modeling assumptions of reinforcement force on LE results, including reinforcement force orientation, and reinforcement tensile load distribution with depth. The suitability of LE for the analysis of two-tiered GRS walls and design implications were then discussed. According to LE results, good agreement existed between LE and centrifuge models in locating failure surfaces. The LE results also indicate that offset distance correlated negatively with the effective overburden pressure on the reinforcement and the resulting confined Tult of the reinforcement. The critical offset distance of 0.7 times the lower tier height was determined when the decrease in confined Tult value as D increases reached a constant value. The LE analyses show that minimum reinforcement length of the upper tier (L1,min = 0.7H1), according to the compound design in FHWA design guidelines, is insufficient, such that failure surfaces do not pass through all reinforcement layers in the upper tier. Last, the effect of offset distance on the normalized reinforcement tension summation coefficient, KT, indicates that single and independent wall models yielded a single consistent KT value. For compound wall models, the KT value decreases as offset distance D increases.