Case Study On The Assessment Of Sinkhole Risk For The Development Of Infrastructure Over Karstic Ground

Karstic dolomite in the Centurion area of South Africa presents significant challenges to the geotechnical engineer. It has been recognised for many decades that sinkholes can occur in the resid- ual soils overlying the Dolomite, but it is not possible to predict their occurrence or their size. Sinkholes present a significant hazard to infrastructure since they occur suddenly and result in a loss of ground sup- port. In designing the Gautrain Rail Link, routed through the Centurion area, it was necessary to manage this hazard in a rational way. Adopting the maximum possible size of sinkhole that could occur and de- signing for this eventuality was considered unrealistic in terms of international practice. This paper pre- sents a risk-based approach that was used as part of the design for the section of Gautrain running over the dolomites to demonstrate that sinkhole risks have been made as low as reasonably practicable. A quantitative risk assessment was undertaken to model numerically the consequence and likelihood of sinkhole occurrence. This approach enabled the risk from sinkholes to be quantified and was used to help define the design requirements for the infrastructure in respect of this hazard.