Dee Subsea provided structural engineering expertise on the Temporary Aggregate Jetty at Hinkley Point C for Costain in 2017 and 2018.
The jetty was constructed to allow the majority of the cement, sand and aggregate required for the project to be imported by sea, therefore minimising HGV traffic on local roads.
We were initially involved in the design of structural ancillaries to aid construction of the jetty berthing island. This included alterations of the berthing island beam details, pile cap alterations, provision of temporary bracing, and the design of emergency ladders.
The berthing island consists of precast deck units supported on steel beams and piles. In-situ concrete was poured between the precast units, and we designed additional steel supports for GRP formwork to facilitate this.
We also designed a steel support structure with permanent formwork which was lifted into position on steel piles to allow a section of one metre thick in-situ reinforced concrete slab to be poured 500m offshore (see below). This included design of lift points, pile support brackets and bolted end connections for connection to the main berthing island steelwork.
A finite element analysis model was used to check the capacity of the piles at the connection with the support brackets when subject to loads from the frame and in-situ slab. This analysis included allowances for the installation tolerances of the piles and formwork support frame.
The main jetty also consists of precast units supported on steel beams and piles. We were involved in preparing an installation sequence for the precast units. The majority of the precast units could not be installed using the lift vessels on site. Also, incremental installation by crane from the jetty deck was not possible as it was identified that the beam cross bracing would be overstressed whilst the crane slewed. Therefore, a solution was developed using a counterbalanced forklift and innovative lift frame to cater for the varying geometry, weight and centre of gravity of the different precast unit types.
Additional information about the Hinkley Point C scheme can be found on the EDF website.
For more information about our involvement on this project, or to find out more about our services and how we can help you, please contact us.