Serviceability state deformation behaviour of two-tiered geosynthetic reinforced soil walls

This paper presents the results of a numerical investigation into the serviceability state deformation behaviour of two-tiered geosynthetic reinforced soil (GRS) walls. A parametric study was conducted using a calibrated finite element model to investigate the key influencing factors, such as the offset distance and reinforcement length. The results of the FE analyses were analysed to identify the fundamental interaction mechanism between the upper and lower tiers and to check the appropriateness of the preliminary design rules set by the FHWA design guideline. The results indicate that the interaction between the upper and lower tiers affects the internal stability of the lower tier while also influencing the external stability of the upper tier. Also, it is revealed that the interaction between the two tiers tends to induce larger wall deformations, leading to larger reinforcement forces at the base of the upper tier compared to an independent wall of the same height. The critical offset distance, beyond which two tiers act independently, is approximately 40% smaller than that recommended by the FHWA design guideline. However, the minimum reinforcement lengths defined by the FHWA design guideline are in good agreement with those determined by the current study.