Tensar International’s TriAx geogrid has been successfully installed by South African World Cup 2010 contractors to overcome poor load-bearing ground encountered on the new Green Point Stadium in Cape Town.
Construction of the stadium, which will play host to a World Cup semi-final in July, was made problematic by the highly variable soil inherent to this spectacular ocean-side setting at the southern tip of the continent.
Led by the joint venture of Murray and Roberts and WHBO, the new 68,000-seater stadium was designed to be set into a deep excavation, to satisfy planning constraints relating to nearby buildings. Initial problems were encountered as a result of the excavated material being placed uncompacted over surrounding spaces. So, when temporary haul roads for access were routed over these areas, considerable ground movement was experienced.
As some of these roads would become permanent roads for stadium access, the routes needed stabilising and because of the tight programme it was decided to carry this out early with the advantage that the haul roads would also benefit.
The contractor had a choice of removing 6-8 metres of the fill, replacing it with properly compacted fill and bringing up to level, or constructing a mechanically stabilised road base with two layers of TriAx geogrid and 400mm of locally-sourced high-quality aggregate.
Choosing TriAx was deemed a success following extensive use over an exceptionally difficult winter. Even severe rain, including a 58mm/hour storm, resulted in minimal settlement or deformation of the new access road.