Precast Enviro-Wall blocks manufactured by Technicrete provided the preferred engineering solution for a retaining wall at the new Monument Park interchange on the R21 highway. The highway links Pretoria and OR Tambo International Airport and one of the off-ramps at the new interchange skirts close to houses in the suburb.
Excavation work for the highway had created a steep embankment and a retaining wall that would be structurally sound, environmentally appropriate and visually pleasing, was required – to stabilise the embankment and to dampen the traffic noise, limiting its intrusion on the nearby houses.
A total of 26 800 Enviro-Wall interlocking blocks were used to build the wall which is 326m long and reaches a maximum height of just under 5m.
Enviro-Wall offers a variety of visual effects. The blocks can be stacked with gaps for plant growth or as a solid engineering structure. In this project, the engineers opted for a solid face and the completed structure features a checkerboard pattern which was achieved by using blocks with ridged and smooth surface patterns alternately.
Dawid Els of Pretoria consulting engineering firm Nyeleti Consulting, says, “The Enviro-Wall system was chosen for its fine engineering qualities, ease of assembly, and the attractive finished structure it could provide.”
In this project, the retaining wall was not built at the conventional 70º to 75º angle but was instead constructed vertically, with a backfill of low-fines to provide added strength and aid rainwater filtration. This construction was space-saving and avoided interference with nearby stormwater drainage and electricity and water lines.
“The result is an unusually attractive off-ramp feature and an engineering solution that works well,” says Els.