All the sinkholes you see on a 10-minute drive through Centurion

Gauteng has a sinkhole problem and it’s arguably the most noticeable in the Centurion municipality that sits between the major metros of Pretoria and Johannesburg, with many roads in the area currently blocked off or inaccessible due to these dangerous and unpredictable events.

It has caused major traffic headaches for residents of the area as crucial thoroughfares such as the N1 highway, parts of the M10, and Main Road in Irene which carries over 20,000 people daily, have either been handicapped or completely cut off to the average commuter who must all now funnel into other routes.

In the most extreme cases, sinkholes have destroyed much more than the road, such as in the case of Clifton Avenue.

These hazards tend to form after heavy rains – like what the province recently experienced – in areas rich with dolomite, as the rock dissolves underground forming a cavity that can collapse into itself at any given moment. They can also be caused by human elements, such as when a leaking pipe drains into the ground.

Sinkholes are nearly impossible to foresee and could take ages to repair as, without complicated and extensive investigations, there’s usually no telling how big they can get.

To illustrate just how prominent the issue is in the Centurion area, we documented the numerous sinkholes we’ve encountered within a short drive from the TopAuto offices in Irene.

To find the exact locations of these dangers, you can click on the underlined links to use the What3Words global navigation system, or manually punch in the three-word sequence connected to each sinkhole.

Solving the sinkhole problem

The sinkhole problem is being tackled from various angles, with practices in place to avoid building roads in accident-prone areas as well as to repair the disasters as soon as they happen.

In the planning phase of a new route, the South African National Roads Agency (Sanral) first performs a process called “ground-penetrating radar” to scan for dolomite and cavities in areas where it wants to lay down the tarmac.

However, in light of around 25% of the land in Gauteng being affected by the mineral, it is not always possible to completely steer clear of it.

The image by Scielo below shows the distribution of “instability events” and dolomite land across Gauteng, with Centurion proving to be one of the most heavily-affected regions.

In the scenario where it’s impossible to avoid the dissolving rock, Sanral said it relies upon “other solutions” to keep road goers safe.

One of these is erecting underground concrete pillars at the onset of a building project in an affected area to reduce the risk of sinkholes damaging the finished structure down the line. This can be seen in the construction of the Gautrain bridge running over the highway around seven kilometres away from the N1 sinkhole.

If the unavoidable happens, though, the agency said that the size of the sinkhole will determine the type of reparations.

A small cavity can be filled with rocks and compacted, but larger ones need more extensive restitutions such as building a reinforced concrete slab above the cavity that would allow a road to be laid on top.

The photos below show the seven sinkholes in close proximity to the TopAuto offices that are severely affecting traffic flow and accessibility in the Centurion area.

Sinkhole 1 – Clifton Avenue

Sinkhole 2 – Hans Strijdom Avenue

Sinkhole 3 – John Vorster Drive

Sinkhole 4 – M10 Bridge

Sinkhole 5 – Main Road

Sinkhole 6 – N1 Flying Saucer Interchange

Sinkhole 7 – Paul Kruger Road