“The physical tests in our facility provide reassurance against analytical and numerical findings modelled by the construction consortium, TM COTU,” said HR Wallingford Project Manager John Alderson. “Detailed testing is important so all the challenges are well understood and a safe and controlled immersion process will be guaranteed.”
The river, its bathymetry, and the trench were modelled in our wave and current basin. We used 4 in-line pumps, each with a 0.3m3/s capacity, to generate the currents. Instruments and dye tracing was used to validate the flows, which are relatively quick at around 1.7m/s to 2.0m/s. Our workshop team constructed tunnel elements from polycarbonate, which was ballast to represent the mass of structure correctly. We also had to model mooring lines and the vessels which were passing by the tunnel installation area.
As well as 6 degrees of freedom forces on the tunnel elements, we also measured forces in the mooring lines, using stain gauges. The motions, in 6 degrees of freedom, of the tunnel element and installation structures were also measured alongside wave disturbance. We modelled a number of sensitivity scenarios for different tunnel element orientations or in case a vessel exceeds its speed limit or strays from the expected route.