This thesis consists of two series of limit equilibrium (LE) analyses of multi-tiered geosynthetic-reinforced soil (GRS) structures using the physical models compiled from literature. In the first part of study, LE analyses of centrifuge 2-tiered GRS wall models were conducted. The objectives include: (1) evaluation of the ability of LE for predicting performance at failure of 2-tiered GRS walls; (2) examination of the design methods for multi-tiered GRS walls in current design guidelines. The variables considered in the centrifuge testing program are offset distance, D, and reinforcement length. Depending on offset distance, these reinforced wall models are categorized as single, compound, and independent walls. The comparison results indicate the LE analysis with a noncircular failure surface can accurately predict the location of failure surface. The maximum tension lines recommended in FHWA design guidelines depict failure surfaces at a long distance from the wall face, resulting in an overestimation of the required reinforcement embedment lengths and conservative design against pullout. Furthermore, a parametric study was conducted to evaluate the effects of wall design parameters on the required tensile strength of reinforcement. Two scenarios of wall configuration were assumed: (1) walls have the same total offset distance with the same total height and; (2) walls have the same offset distance with same height for each tier. The results of parametric study in the first scenario indicate the required tensile strengths of reinforcements are the same for walls with the same total height and total offset distance. The required tensile strength of reinforcement increases as the number of tiers increases in the second scenario.
In the second part of study, LE analyses of a 4-tiered GRS slope were conducted. The purpose is to investigate three failure cases of a 4-tiered GRS slope under earthquake and heavy rainfall conditions. This study identified that these failures may be attributed to the existence of an impermeable clay layer, which had been overlooked during the stages of site investigation and design. This study also demonstrated that the failure mechanism predicted by LE analyses agreed well with the field observation and the finite element predictions under different field conditions.

This thesis consists of two series of limit equilibrium (LE) analyses of multi-tiered geosynthetic-reinforced soil (GRS) structures using the physical models compiled from literature. In the first part of study, LE analyses of centrifuge 2-tiered GRS wall models were conducted. The objectives include: (1) evaluation of the ability of LE for predicting performance at failure of 2-tiered GRS walls; (2) examination of the design methods for multi-tiered GRS walls in current design guidelines. The variables considered in the centrifuge testing program are offset distance, D, and reinforcement length. Depending on offset distance, these reinforced wall models are categorized as single, compound, and independent walls. The comparison results indicate the LE analysis with a noncircular failure surface can accurately predict the location of failure surface. The maximum tension lines recommended in FHWA design guidelines depict failure surfaces at a long distance from the wall face, resulting in an overestimation of the required reinforcement embedment lengths and conservative design against pullout. Furthermore, a parametric study was conducted to evaluate the effects of wall design parameters on the required tensile strength of reinforcement. Two scenarios of wall configuration were assumed: (1) walls have the same total offset distance with the same total height and; (2) walls have the same offset distance with same height for each tier. The results of parametric study in the first scenario indicate the required tensile strengths of reinforcements are the same for walls with the same total height and total offset distance. The required tensile strength of reinforcement increases as the number of tiers increases in the second scenario.
In the second part of study, LE analyses of a 4-tiered GRS slope were conducted. The purpose is to investigate three failure cases of a 4-tiered GRS slope under earthquake and heavy rainfall conditions. This study identified that these failures may be attributed to the existence of an impermeable clay layer, which had been overlooked during the stages of site investigation and design. This study also demonstrated that the failure mechanism predicted by LE analyses agreed well with the field observation and the finite element predictions under different field conditions.

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