Rawcliffe Bridge flood defence improvements scheme

Abstract

The £1·6 million Rawcliffe Bridge project forms part of the Environment Agency’s Flood Protection Project between the Aire and Calder Canal and the Dutch River in Yorkshire. The unique Trenchmix system has been successfully used to construct a 2·2-km-long and 3- to 6·5-m-deep low permeability cut-off barrier as part of the flood defence upgrade works. Atkins identified the potential for this technique at the site with Bachy Soletanche Limited joining the project team to offer specialist design and construction expertise for the Trenchmix solution. This collaborative approach helped to refine the specification and optimise the design, which ensured that the complex ground conditions and hydrogeological risks were managed effectively. This paper describes the Trenchmix process and presents the key components of the scheme: understanding the geology of the site and the complex ground and groundwater conditions; selection of an appropriate solution to address the risk of uplift and piping failure; the binder dosage trials in order to determine the cementitious contents required to achieve the required permeability and strength; and the quality assurance testing required to demonstrate compliance with the end-product specification.