THE PROBLEM
An access ramp formed from loose, weak, variable fill which was being utilised as a temporary haul road would need to be adapted as a heavy duty block paved road in the permanent works. There was no time in the programme to halt works in order to excavate the poor material and re-compact it to provide a stable foundation for the road.
THE SOLUTION
Two layers of Tensar TriAx™ geogrid were placed in the road sub-base to eliminate excavatation of up to 8m of fill material and to also reduce the possibility of differential settlement.
PROJECT DESCRIPTION
The new stadium was subjected to stringent planning regulations including a limit on the finished height. As a result, vast amounts of excavated highly variable material were placed around the construction site. In one particular section this fill formed a ramp supporting a haul road which was showing signs of deformation and heaving and as it was due to eventually be block paved, remedial action was required.
The contractor was faced with the possibility of excavating the uncompacted fill and reconstructing the sub-base. This would have had a major impact on site traffic, construction programme and been an unjustifiable cost the client could not afford.
The consultant, 7 Sea Geoscience, contacted Tensar local Distributor, Geotechnologies SA Ltd to visit site and put forward a proposal. Their accepted proposal was to leave all material in-situ and construct the sub-base incorporating 2 layers of Tensar TriAx. This was used to reinforce the haul road, the surface of which would later be trimmed to form the foundation for the permanent road, which was also stabilised by the same geogrids.
