SMEC was responsible for developing a timely solution that would ensure the pass could remain open to traffic travelling between the towns of Franschhoek and Villiersdorp, while not compromising on the safety of road users.
SMEC’s scope of work included:
- Repairing damaged drainage infrastructure
- Repairing damaged road surfacing
- Implementing erosion-mitigation measures
- Stabilising a progressive deep-seated slope failure on the lower western flank of the pass
The project was highly visible and recognisable, and the design involved the use of a number of innovations in order to effectively mitigate at a reasonable cost, a proportion of the risk associated with the frequent failures.
In keeping with the heritage of the route and the surrounding environment, an aesthetically pleasing and environmentally friendly solution was required.
Located 60 km east of Cape Town, Franschhoek Pass (R45) is one of South Africa’s iconic mountain passes. In 2013, unseasonably high rainfall in the region led to severe slope instability along the route, leading to numerous traffic closures.
SMEC was engaged by the Western Cape Department of Transportation and Public Works to establish emergency remedial measures for the preservation of this vital transport link and popular tourist route.
The solution to the progressively failing slope involved the use of an unconventional slope stabilisation method, which included:
- Optimisation of the slope geometry to reduce the slope’s gradient
- Improvement of surface and subsurface drainage
- The use of high strength steel wire mesh and large steel anchor plates where anchor loads were greatest
- The use of soil nails interspersed between the drains to increase the strength and resilience of the slope
- Installation of an erosion control matt between the subsoil and steel mesh layers to support the revegetation process through improved seed germination
SMEC undertook detailed analyses of geotechnical and structural elements to ensure that the steel mesh and soil nail solution effectively distributed the high anchor loads into the mesh.
- South Africa
- Technical Area:
- Western Cape Department of Transportation and Public Works