Reliability-based structural design of retaining walls supporting spatially variable soils

Abstract

The design of retaining walls is affected by spatial variability in the properties of the retained backfill and the foundation soil. In practice, the conventional approach for designing retaining walls is deterministic in nature and is based on ensuring acceptable design factors of safety for different limit states of wall failure. The only exception is the design method that is available in Eurocode 7, where partial load and resistance factors have been recommended to ensure a target level of safety in the design. Although these codes are considered to include the uncertainties in the design load and capacity, the recommended partial safety factors may not realistically incorporate the impact of spatial variability in the properties of the supported backfill and foundation soil on the design, since the calibration studies that were conducted to determine the safety factors were not based on realistic random field modeling of the soils involved. In addition, existing reliability-based design approaches for retaining walls focus on the failure in the soil and do not include design aspects of the structural behavior of the wall. The main objective of this thesis is to quantify the level of risk associated with the design of a cantilever retaining wall using the conventional deterministic design approaches and approaches that are based on partial factors of safety (ex. Eurocode 7). The objective will be attained by utilizing random fields that represent the variability in the backfill and foundation soils in the finite difference software FLAC 2D®. The effect of the properties of the random field on the design of the retaining wall will then be investigated to provide recommendations that would aid the design of cantilever walls supporting cohesionless backfill.