230-metre long tunnel the solution for 30m deep valley
Dualling the A465 Heads of the Valleys road between Brynmawr and Tredegar, south Wales “can act as a catalyst for economic regeneration” according to a recent article in Construction News and the Construction News website (subscription).
The report by Daniel Kemp focusses on one particular problem area – “one section of the road required Carillion to build a number of new structures in difficult conditions.”
The original Carno Valley crossing solution was earmarked as a 170m long viaduct but the huge amount of excavated material from the length of the project suggested possible alternatives. The ultimate solution proved to be a precast concrete arch of impressive dimensions – 18m wide, 9m high and 150m long.
Precast concrete segments
PCE, on behalf of Carillon, erected a tunnel using Reinforced Earth’s TechSpan® precast concrete segments. PCE installed some 147 arch units weighing up to 20 tonnes each to form the tunnel and a further 18 scalloped units which were placed at the entry and exit to the structure. Each segment was lifted into position by using an 80 tonne crawler crane.
Carno timelapse video
The YouTube video, courtesy of Carillon, shows time-lapse images of the construction of the tunnel.