Numerical investigation of the lateral response of pile groups in sand under local scour conditions

Bridge foundations located in a water flow environment commonly experience scour, which can lead to significant drops in the soil elevation immediately surrounding the foundation. This has significant ramifications for lateral bearing capacity as well as the integrity of the supported superstructure. While pile groups are one of the most foundation systems for bridges, current research on scouring effects has been largely limited to single piles. This paper fills this gap through the use of 3D finite element (FE) analysis, validated using centrifuge tests reported elsewhere in the literature. Results from a parametric analysis is described exploring the effects of the scour hole geometry, defined by the depth and slope angle, on the lateral behavior of pile groups. In particular, the influences on the load–displacement and bending moment and soil resistance distributions with depth for each pile within the group are considered. The results show that scour can have a significant detrimental influence on the lateral response of a pile group. An increase in the length of the pile group is also shown to significantly reduce the sensitivity of the lateral bearing capacity of the group to scour.