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.

Case study – precast tunnel for watercourse diversion in Wales »

Carno timelapse video

The YouTube video, courtesy of Carillon, shows time-lapse images of the construction of the tunnel.