BACKGROUND:
The initial work on this northeastern coastal site was a clean-up of the coastline, preventing deposits of landfilled waste from decades of colliery waste being washed into the sea. Around 1000 tonnes of hazardous and non-hazardous materials, including asbestos, rubber and plastic were removed from the site. 95,000 tonnes of colliery spoil was excavated and processed to restore the natural coastline, protecting the surrounding marine ecosystem & also ensuring public safety for local residents and tourists.
Work then began on the creation of a working platform for a new waste processing plant on the site. Traditional construction methods for this could not be used as the base was largely sand soil with a California Bearing Ratio (CBR) of 3%, indicating a very weak or poor soil subgrade which has only 3% of the bearing strength of standard crushed rock. Such a low value required ground improvement and soil stabilisation.
Geotechnical specialist from the SIG Infrastructure team, Jason Bland, had been discussing this project with the contractor BAM and Agent Jonny Purvis, from when it was approved in 2019. He worked closely with them to look at various solutions and brought in specialist suppliers Naue and PRS to help design an effective product solution.
CHALLENGE
The challenge was to create a suitable compound solution set into the sand dunes and to utilise the sand on site as the infill material capping it off with 70mm of imported quarried stone.
The development was on a tight timeline, and there was a requirement to minimise the use of imported aggregates. Unreinforced solutions were quickly ruled out, as none were capable of utilising the existing on-site sand.
Once an area had been fixed for the processing plant, the teams set about a full design proposal based on utilising site won sand from the sand dunes. They looked at various options before settling on the composite design using both Naue and PRS materials to create the ultimate hybrid platform, reusing the sand as an infill on the geogrid.
The design was undertaken by PRS and ratified by the BAM Temporary Works Design Team.
The design progressed utilising a composite solution incorporating Naue Combi-grid 30/30 Q1 & PRS Neoloy 330/150 C.
SIG Construction Accessories were instructed to supply the materials required from their local branch at Tyneside. SIG also provided toolbox talks and training to assist with site installation.
PRODUCT
Neoloy® Tough-Cells from PRS were selected as the only viable solution capable of using local sand and making it perform stronger than gravel. The high reinforcement factor enabled a reduction of the base layer thickness by 50% saving additional in-pace construction time and costs. The section developed was made up of:
– Naue Combigrid 30/30 Q1 GRK 4C (Base)
– PRS Neoloy 330/150 C (above base)
– 200mm Site Won Material
– 50mm 6f5 imported stone
RESULTS
The project team identified a solution capable for effectively stabilising the on-site sandy soil, and utilitising the sand on site eliminating the need for imported aggregate. Overall, the solution significantly reduced project costs, the carbon footprint, and vehicle movement to site. All contributing to faster site readiness and simplified logistics.
TESTIMONIAL
“From the initial enquiry through to the successful construction of the Processing Area, the expertise and input from SIG was invaluable. They took our concept and designed a fully compliant working platform, which reduced prelim time on site & associated costs, as well as having a significant reduction in C02 emissions, by eliminating large quantities of imported aggregates. The professional and proactive approach from Jason and the wider team was greatly appreciated by BAM & ensured a streamlined execution from ‘cradle to grave’ which met the project requirements.” Jonny Purvis, Project Manager, BAM UK & Ireland.
