The first layer of Wrekin’s E’GRID™ rigid biaxial geogrid was rolled out over the top of the MT1000. 250mm of 6F5 aggregate was placed and then compacted by a roller, followed by another layer of geogrid and a further 250mm of 6F5.
The substantial half metre reduction in foundation thickness over a conventional founding section reduced the total excavation and export of earthworks, therefore reducing the overall import and compaction of aggregates required.
After construction of the founding layers, plate bearing tests confirmed the in-situ performance at the formation level, on top of geogrid stabilised capping layers. Five plate bearing tests were taken on the inner 20 metres of the performance trial area, with the highest result being 47% and the lowest result being 18.7%. The performance trial area therefore exceeded the preliminary requirement of 15% at formation level.
A further granular sub-base layer was installed and tested, producing results between 70% and 100%, far exceeding the requirement of the pavement foundation. This confirmed that the geogrid solution and application was suitable for adoption to overcome the identified problems.
Altogether, this project demonstrates how value engineering solutions such as geogrids can be used to solve general and site-specific issues for the housing sector, while simultaneously saving contractors time and money.
