Restoring Flood Defences to Peak District town
The River Derwent flows through the Derbyshire town of Matlock. A severe storm event in February 2022 caused a 20 metre section of flood defence wall along the river to collapse. In response, the Environment Agency commissioned works to replace the flood wall behind businesses in Crown Square and protect Matlock from future river flooding.
Owing to the town centre location and close proximity of the Grade II* listed heritage stone bridge, coupled with extremely tough Derbyshire limestone ground conditions, our Giken Supercrush Silent Piling solution was identified as the only viable way to install the necessary sheet piles vibration-free.
Reducing the impact on local residents and businesses
The sheet piles were installed using the Giken Supercrush method, whereby the ground is augered at the same time as piles are silently pressed-in, without causing any vibration. This was necessary because of the location, nearby sensitive structures, and extremely hard ground conditions.
Two of our Giken Supercrush Silent Pilers worked side by side, facilitated by an 800-tonne lift capacity mobile crane (officially named by locals as ‘Lifty McShifty in a naming competition’), which functioned from the nearby A6 Derwent Way, as there was no landward access to the river.
Prior to works commencing, we attended a community drop in event in Matlock, which gave locals the opportunity to view designs for the new replacement flood wall and learn more about our silent and vibration-free solution. The event was organised by the Environment Agency and partners, Derbyshire County Council and Derbyshire Dales District Council.
Keeping it on programme
Working closely with main contractor Jackson Civil Engineering and the Environment Agency, we were able to maximise the construction programme, concluding our main piling operations in time for the Christmas break. This meant flood protection from the river could be swiftly reinstated to the residents and businesses of Matlock during site closedown.
Limited access no problem
There was no landward access to the river, so a temporary safe working platform constructed from aggregate stone was required to be built out into the river.
In total, Ivor King installed 66No. PU32-0.5 steel sheet piles of up to 11 metres in length into hard limestone, using two of our Giken Silent Pilers operating in Supercrush mode.
The silent Giken piling equipment presses each successive pile to full depth, using a pitch and drive procedure, whilst ‘walking’ on the previously installed piles, by raising its body and travelling forward to the next position.
Sheet piles are fed by crane into the enclosed chuck (or pressing jaws) of the machine ready for installation.
The initial sheet piles were installed from the Giken Silent Piler’s reaction stand placed on steel mats within the temporary stone platform area. Concrete kentledge blocks, placed on the Giken’s reaction stand, were utilised to generate enough reaction force for installation. Once the starter piles had been installed, the Giken could be placed atop the pile line and continued pressing sheet piles using reaction force from the previously installed piles.
Sheet pile flood wall receives the heritage treatment
Whilst sheet piles may be extremely effective in terms of offering robust flood protection, the aesthetics of the replacement flood wall were later upgraded to match the heritage look and colour palette of the area.
The sheet piles were encased in concrete to which locally sourced stone cladding was added to complete the look, in keeping with the adjacent old stone Matlock Derwent Bridge, part of which dates back to the 13th century.