Behavior of Laterally Loaded Piles under Scour Conditions Considering the Stress History of Undrained Soft Clay

Scour can remove soils around bridge foundations and result in reduced bridge capacity. Because most bridge failures have been associated with scour events, it is important to evaluate scour effects on bridge safety. In practice, an evaluation of the performance of bridge piles under scoured conditions is usually achieved by simply removing soils from around the piles while possible changes in stress history of the remaining soils are ignored. In reality, the remaining soils undergo an unloading process when scour removes soils from above the remaining soils. This process increases the overconsolidation ratios of the remaining soils. In this study, the stress history of soft clay was considered in the analysis of laterally loaded piles using the $p\text{-}y$ method. To account for the stress history effect, the conventional $p\text{-}y$ curves for the soft clay were modified to evaluate the undrained responses of the laterally loaded piles at different scour depths. A case study was used to compare the computed results by considering and ignoring the stress history effect. The results showed that consideration of the stress history effect resulted in a 21.8–32.7% reduction in ultimate soil resistance. Ignoring the stress history of the soft clay led to an unconservative design of the laterally loaded piles under scour conditions.