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Capels Mill Progress Report No. 9

Capels Mill Update

Work progresses at the Capels Mill site. This contract, to create a completely new canal route through the railway viaduct, is the largest piece of canal civil engineering tackled since restoration of the Cotswold Canals began.

Striking changes

The first picture looks through an arch from the western side of the viaduct.

It shows the exposed piling wall beyond the large pile of dark material in what will will become the navigation arch.

Mud, mud – glutinous mud

The overwhelming feature that impresses is the extent of the works and the huge amount of mud present.

The Alun Griffiths Contractors team appear undaunted by the conditions. One team member on site answered the question – ‘How has it been for you recently’ with a big grin and some words delivered with a Welsh lilt – “ Very Cold and wet… oh… and Very Wet and cold too!”

Captured in concrete

Clearing the material from the piled wall has revealed some interesting artefacts that present immovable evidence of times past.

The fact that the piles were driven down through what was once Stroud’s domestic waste tip is revealed by a shoe and a kitchen ladle encapsulated for ever in concrete.

Careful monitoring

The material that has been removed from the face of this wall of concrete piles is carefully monitored so that only the safe and clean material is taken off site.

The remaining domestic waste affected material will be capped with a combination of a clay material known as bentonite. Sheets of geotextile matting, crushed concrete and a liberal topping of subsoil and topsoil material are also applied. Completion of the process will allow landscaping to create a Stroud’s new waterside park area.

Changes in the East

The striking changes are to be seen at the far Eastern end of the site.

Pictures three and four show a matrix of three metre deep 'bottom driven piles'.

The pile casings protrude through a surrounding expanse of freshly laid concrete.

Click here to see the rest of Mike Gallagher's photos taken at Capels Mill on Monday

The fourth picture shows how close the work has progressed towards connecting with the original canal. 

Next steps

The piles and the concrete area will provide a supporting base for the casting of the concrete channel that will carry the canal closely alongside the River Frome.

The term 'bottom driven piles' perhaps calls for an explanation… so here it is.

Bottom driven piles are formed by driving a crimped closed end, sacrificial thin wall steel casing into the ground using an internal drop hammer. 

The internal drop hammer drives onto a dry concrete plug/packer at the toe of the casing and additional casings sections are added as the pile is advanced.

When the casing has been advanced to its predetermined design length the steel reinforcement is placed and the pile bore is filled with concrete. This is a displacement technique, meaning no spoil is produced making it particularly effective on brown field sites.

This method is used in sensitive environments where the use of driven techniques are generally precluded. Piles installed using this method can also be positioned in very close proximity to existing walls and structures. So, now we know.