ABSTRACT
Hinkley Point C in Somerset, UK is a new nuclear power station currently under construction. Three offshore TBM tunnels beneath the Bristol Channel have been constructed to bring in and then discharge water to cool the reactors. Each tunnel is connected to two offline shafts by short connecting adits. The offline connections concept design recognised that mitigation of the risks associated with groundwater as being critical to the overall success of the connections. Development of an appropriate strategy to control groundwater during construction has therefore been fundamental to the development of the proposed temporary works detailed design.
This paper describes the ground investigation methodology and rock fissure grouting undertaken prior to the TBM segment removal to allow for safe and efficient excavation of the connection ensuring that groundwater inflows into subsequent excavation stages were manageable. A summary is provided of the ground conditions and the approach to target grouting works. During the grouting works the groundwater inflow was measured to provide information on each grout stage together with an assessment of the grout injection characteristics to aid confirmation of the ground model and performance of the grouting works. A 3-dimensional ground model assisted the planning of grouting as well as providing details of the location and records of groundwater inflows recorded during the works.
