Component and System Reliability Assessment of Landfill Cover Systems Using Pseudostatic and Pseudodynamic Methods

Abstract

This paper assesses the reliability of landfill veneer cover systems against direct-sliding failure (DSF) and uplifted-floating failure (UFF) modes using the second-order reliability method (SORM). Variability in stability number due to cohesion, interface cohesion, friction angle, horizontal seismic acceleration coefficient, and phase changes are considered. Formulations for the first-order reliability method (FORM), SORM, and Monte Carlo simulations (MCS) are presented, with emphasis on the precision of SORM over FORM. A novel framework for system reliability–based design optimization (SRBDO) is introduced, addressing interdependencies between DSF and UFF modes. The results highlight the significant influence of the lowest component reliability index on system reliability. For the given design conditions, the system reliability index is obtained as 1.55, significantly influenced by the component reliability indices of 1.55 and 9.29. In addition, this study provides a comparative analysis of reliability indices obtained using SORM for static, pseudostatic (PS), and pseudodynamic (PD) methods. Moreover, system reliability–based design charts are generated to estimate allowable cover soil thickness to ensure concurrent reliability in DSF and UFF modes. It is noted that an increase in the value of the horizontal seismic acceleration coefficient from 0 to 0.30 results in a 77.27% increase in the allowable thickness of cover soil. The computational framework of Monte Carlo simulations, first-order reliability method, and second-order reliability method proposed in this study can be utilized to develop an optimum and reliability-based design of municipal solid waste landfill slopes, geosynthetic-reinforced soil slopes, retaining walls, embankments, and other geotechnical structures. Considering the variability associated with the design parameters enables the practitioners to make well-informed decisions regarding the selection and specification of materials. The system reliability framework presented in this study allows for a more comprehensive understanding of the interdependency between the different modes of failure of a system. The insights of this study can be utilized to develop more robust designs of structures equipped to withstand various failure modes. The comparison of reliability indices obtained using the static, pseudostatic, and pseudodynamic methods enables the practitioners to adapt design approaches to varying environmental and loading conditions, ensuring the long-term stability of the structures. The generation of system reliability–based design charts offers practical tools for estimating the allowable thickness of cover soil while ensuring reliability against both DSF and UFF modes simultaneously. Moreover, the findings of this research contribute to the establishment of global design standards for ensuring seismic stability in veneer cover systems.