Reliability-Based Structural Design of Retaining Walls Supporting Spatially Variable Soils

The performance of retaining walls is affected by spatial variability in the properties of the retained backfill. In practice, the conventional approach for designing retaining walls is deterministic and is based on ensuring acceptable factors of safety for different limit states of wall failure. One exception is the design method in Eurocode 7, where partial load and resistance factors are recommended to ensure a target level of safety in the design. The main limitation of partial load and resistance factors is that the recommended partial safety factors may not realistically incorporate the impact of spatial variability of the backfill properties, because the calibration studies that were conducted to determine the safety factors were not based on realistic random field modeling of the soils involved. Another limitation is that existing geotechnical reliability-based design approaches for analyzing retaining walls focus on failure in the soil and do not include design aspects of the structural behavior of the wall itself. The main objective of this study is to quantify the probability of failure associated with the design of a cantilever retaining wall using approaches that are based on partial factors of safety (Eurocode 7). The objective is achieved by utilizing random fields that represent the variability in the backfill in the finite difference software FLAC 2D. The effect of the properties of the random field on the design of the retaining wall are investigated to provide recommendations that can aid in the design of cantilever walls supporting cohesionless backfill. Results indicate that the partial load factors recommended by Eurocode 7 may not meet safety requirements, particularly for high uncertainties in the backfill friction angle and for large vertical correlation lengths.