A bespoke lime and cement soil stabilisation mix is aiding the redevelopment of derelict railway land in the centre of Gloucester.
Essex-based specialist Geofirma Soils Engineering is working on the 25,000 sq m site, earmarked for development into a giant £34m retail development under a £250,000 contract with client Barnwood Construction.
The site has lain derelict since the 1980s, but the latest move will see it transformed into a retail scheme focused on a supermarket for Morrisons.
Engineers at Geofirma analysed soil samples from the site and developed the bespoke lime and cement stabilisation mix, which is being applied using its Firmafil and Firmabase techniques.
With Firmafil, site-excavated material is treated with the stabilisation mix and replaced as fill to give a minimum 5 per cent California Bearing Ratio specification.
The Firmabase specification enables Firmafil material to be re-treated to a depth of 300 mm and a CBR specification of 30 per cent.
“This route also has environmental benefits by reducing the amount of materials going to landfill and the number of truck movements”
Steve Dunn, Geofirma
This process brings the soil up to the strength and stability required for structural fill and capping/sub-base layers, eliminating the need to import good fill and dramatically reducing the requirements for imported stone.
According to Geofirma general manager Steve Dunn, the site has proven ideal for in-situ soil stabilisation and underlines its environmental advantages.
He said: “In addition to being a quicker and cheaper method, this route also has environmental benefits by reducing the amount of materials going to landfill and the number of truck movements to and from the site.”
The eight-strong Geofirma site team is using its fleet of soil engineering equipment, including its Wirtgen W2500R with integrated hoppers, to minimise dust creation and ensure the stabilisation works are delivered in just eight weeks.
Contracts manager at client Barnwood Construction Adam Welland has been happy with the results despite poor weather on site.
He said: “I am even more pleased that Geofirma has worked with my site team to complete the ground engineering in a way that has allowed other trades to progress despite the poor weather.
“That has been of tremendous benefit given the restricted timescales of the overall project programme.”