A new and innovative engineering approach is being used to strengthen the Grade II listed stone quay and parade along Swanage’s historic seafront.
The old stone structure was constructed in the early 19th century, so Purbeck-quarried stone could be loaded onto boats and shipped up to London.
The repair work will start on Monday 5th October 2020 and is expected to be completed in five days. For safety reasons, the area will be closed to pedestrians for the duration of the work.
The red line shows the pedestrian footpath that will be closed for the duration of the work. The blue line shows the alternative route.
Weakening of the structure
Dorset Council’s engineering asset manager, Grant Armfield said:
“With these older structures, there are natural voids. They’re not large but just small spaces that lead eventually to a weakening of the structure. There was more art than science in how they were originally built!
“Using specialist ground penetrating radar, we’ve examined the Stone Quay and Parade which has revealed a number of voids. In order to re-stabilise the ground, we could dig holes and fill them with concrete but some are one metre deep, so that’s not really desirable nor practical.
“So we’ve gone for a new emerging technology that involves drilling a hole down into the structure and then injecting a polymer grout under a low pressure. It’s a type of foam that will fill the gaps and because it’s lightweight it will both strengthen and stabilise without adding weight.
The Stone Quay is a popular place to sit and admire the view
Sympathetic way to retain its character
Because of the age and character of the stone quay and parade, the work needs to be done in a sympathetic way to retain its character, which includes avoiding any damage to the stone setts.
The old tramway track from when rail trucks were used to bring the stone from the road down to the quay, also has to be preserved. Grant Armfield added:
“It can be done quite quickly without too much disruption and won’t damage the stone setts or the rails. The drilling will be through the joints and then specialised mortar will repair the joints.
“Once done, this should strengthen the structure for some considerable time, without being too invasive and unduly disturbing the historic structure.”
The old tramway rails are a historic feature along the Parade
Regular pounding from the waves
The Stone Quay and Parade takes a regular pounding from the waves, so needs to be maintained well but not all the gaps in the structure will be filled. Grant Armfield explained:
“When the wave hits the wall, some of the water penetrates the structure and then pours out at the bottom – we’re not planning to fill those in, as this reduces the power of the wave and allows the energy to be dissipated.”
“Great opportunity to use these polymer grouts”
“This is a great opportunity to use these polymer grouts, which are an emerging technology. We could use this method elsewhere like the Cobb in Lyme Regis or in Weymouth Harbour.