Design Methodology for Bridge Abutment Pile Group Foundations – A Case Study

A reliable assessment of immediate and long-term deflections is vital for a cost-effective pile group design supporting a bridge abutment. This paper reports on some key challenges involved in the design methodology developed for the assessment of 8 over bridges on a railway scheme in UK. The unconventional construction sequence involved placement and locking of the bridge deck prior to backfilling. This resulted in reduction of the allowable translational and rotational movements of the abutments’ foundations to eliminate the risk of exceeding the bearings’ movement tolerances. To test this scenario and based on engineering judgement, careful interpretation of the available field, laboratory and numerical analysis results was carried out, and the use of at-rest (K₀) static earth pressure is considered to be suitable in pile design for the case where the foundations are required to be comparatively rigid to meet the above performance criteria. Also, as part of the design process, the output of linear and non-linear analysis from commonly used pile group analysis software packages: Repute and PIGLET were compared with finite element analysis using Plaxis 3D which are presented.