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Reliability analysis of internal and external stability of geosynthetics reinforced soil retaining walls

In the traditional design of geosynthetic reinforced soil walls (GRSW), allowable stress design (ASD) and semi-probabilistic design (SPD) approaches are used to determine the factors of safety against the failure mechanisms. However, these approaches cannot explicitly consider the uncertainties in the design process, especially geotechnical uncertainties which are typically project specific. The present paper introduces a framework for the reliability design of GRSW to explicitly address uncertainties in the design process and account for the actual safety and reliability level of a given design. The basics of probabilistic analysis and design for the internal and external stability limit states of GRSW are explained, and reliability analyses of GRSW are put in a rational framework, where concepts are general and can be applied to any GRSW for which the stability can be expressed by limit state functions, even if the present paper addresses only vertical walls. The limit state functions for the five failure mechanisms of internal and external stability are defined, and are used to calculate margins of safety in terms of probability of failure through Montecarlo simulations, where all parameters can be set as either deterministic (with no associated variability) or probabilistic (with associated variability). The probabilistic analyses can be carried out repeatedly by changing the deterministic and the stochastic parameters, and/or their associated variability. Results can provide a useful decision-making tool for preliminary design of GRSW based on target reliability levels. An example is presented to demonstrate the significance of the proposed framework.