Lifting a 183 t concrete digester roof safely and cost-effectively with hydraulic bottle jacks

Abstract

A 183 t conical concrete roof of a cylindrical anaerobic digester tank at a UK sewage treatment works had to be lifted 150 mm to repair the seal underneath it. Due to limited space for a crane, an incremental hydraulic jacking procedure was used, with 32 bottle jacks in pockets cored out from the top of the concrete tank wall. This paper describes the temporary works design methodology, the extensive planning for risk mitigation, the practical implementation strategy and the lessons learned from using this safe and cost-effective approach.