A465 Dualling between Brynmawr and Tredegar, South Wales

摘要

The A465 Heads of the Valleys road was constructed as a three lane highway, and sections of the route have since been widened to dual two lane. The Section 3 improvement works for 7.8km of road between Brynmawr and Tredegar is currently under construction; as well as online widening there is 4.7km of new offline construction. The scheme is promoted by Welsh Government, partly funded by the EU, and delivered as an ECI Design and Build contract valued at £120M. There are many ground engineering challenges on the scheme which include past mining activities within the South Wales Coal Measures which required extensive investigation and mitigation measures. The route crosses a number of watercourses which has required a range of solutions; including an 18m span precast arch within a 30m high embankment. The earthworks for the scheme are designed to result in no offsite disposal or import of fill materials. Along the online widening sections various forms of retaining structures have been adopted. As the scheme has progressed and actual ground conditions verified, optimisation of the design solutions has been undertaken. The successful integration of design and construction has generated real benefits, with innovative and cost effective solutions identified. The paper gives an overview of the ground engineering aspects, highlighting some of the challenges addressed, and outlining how solutions were developed. Emphasis is put on the value of collecting and disseminating information during the works to refine the design, supported by close collaboration between members of the project team.