A4046 Cwn Relief Road

The A4046 Cwm Relief Road contract was for a new bypass to the village of Cwm in Gwent, South Wales and has a 0.5km long viaduct as the main structure. Carillion Piling undertook piling and barrette construction for the project.

The viaduct required construction of 13 barrettes to provide the foundations for 11 piers and 2 abutments. The barrettes were excavated using rope suspended diaphragm wall grabs. A bentonite fluid was used to provide support for the barrette during excavation.

The barrettes were 8m wide by 1m thick in plan. Barrette depth varied from 12m to 18m. All of these barrettes were founded in underlying bedrock. This work was carried out on a hillside in limited space adjacent to the Newport to Ebbw Vale Railway. In addition to these barrettes, contiguous piled retaining walls were constructed. 105no x 1200mm diameter and 196no x 1800mm diameter piles were construction using temporary casings.

Client: Mowlem Civil Engineering
Equipment used: Sennebegen 670 crane and grab
Casagrande C50, Casagrande RM21
Value: £1.5m