Case Study: Edinburgh St James – Embedded Pile Retaining Wall Design

At 1.7 million square foot, Edinburgh St James (ESJ) is one of the largest and most significant regeneration projects currently underway in the United Kingdom (UK). This mixed-use development situated in the heart of Edinburgh, Scotland includes a retail, leisure, hotel and residential offering, with car parking located within a three-level basement reaching into the bedrock up to 22m below ground level. A case study from the Edinburgh St James project is presented, detailing the design of the embedded retaining wall. The case study shows how monitoring data can be used in the context of the Observational Method (OM) to design more efficiently to benefit the project. The OM is a design approach applied in geotechnical construction where site measurements are used to optimise construction methodology and can be done either ab initio (from the start) or ipso tempore (in the moment). The case study shows the OM method applied ipso tempore. Design efficiency could be further enhanced by adopting the OM ab initio, which allows more time to develop the necessary decision framework and secure the agreement of all stakeholders. Furthermore, future designs can become justifiably more efficient by using data collected by sensors in back analysis tasks to enhance understanding of structural-geotechnical stiffness and strength. We conclude that through early collaboration between the client, contractor and design teams, construction optimisation can bring about cost reduction, a faster programme and improved sustainability outcomes for the project.