Design and construction of the chalk earthworks for the A41 Aston Clinton Bypass

The A41 Aston Clinton Bypass is 6.5 km long and was opened in 2003. It was the last link in the continuous dual carriageway road that now runs all the way from the M25 motorway to the south-eastern outskirts of Aylesbury. A large cutting in the chalk at Tring provided the bulk of the fill used to construct the embankments over the western half of the scheme. The alignment runs through the lower part of the chalk geological sequence – through what was previously known as the Middle and Lower Chalk.

Innovations on this project included the use of the self-cementing characteristics of the white chalk for the capping layer. During the construction there were detailed inspections, which included site visits by the BGS, of the Lower Chalk (grey chalk), Upper Greensand and Gault Clay cuttings, as it proved difficult to differentiate between these materials, particularly with localised faulting present.