Civil engineering contractor MJ Church has started work on a project for National Highways to stabilise an embankment that carries a major road near Bath.
The A36 has been closed between Limpley Stoke and Monkton Coombe until next spring while works take place.
National Highways said it had been aware of minor cracking along this section of the road for more than a decade when routine maintenance in 2021 uncovered signs of "exacerbated instability" within supporting earthworks.
Up to 100m of ground has moved and the project will see 200m of the road worked on to provide resilience.
A piled wall will vary from 4m to 9m in height, although much of this will not be visible. Most of the piles used will be 600mm in diameter, with a section of reduced-width piles of 450mm diameter. They will have a capping beam 1m wide.
The project will also include rock descaling works and installation of rockfall netting to the rock cutting adjacent to the northbound carriageway to protect customers from potential rock falls.
National Highways added: "On the viaduct itself we will be completing masonry repairs, and to the retaining wall to the north of the viaduct we will be completing some minor masonry repairs to the large retaining walls again adjacent to the northbound carriageway."
"The section of the A36 which will be subjected to the renewal is known to be in an area of landslide deposits over the bedrock geology," added the body in a statement to GE.
"However, specifically on site we will likely encounter embankment-fill from the construction of the A36 as well as the landslide deposits."
National Highways described the underlying bedrock geology as "weak to very weak limestone" with "solid" bedrock "at depth".
"Additionally due to local structural geological constraints, it is expected that siltstones and mudstones of the Bridport Sand Formation and Charmouth Mudstone Formation respectively will also be encountered."
WSP is principal designer for the works.
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