Karst Risk Assessment for Underground Engineering: Comparison of the KarstALEA Method with a Random Karst Distribution Approach

Many recent tunnel constructions around the World have shown that uncertainties related to karst processes are a major issue, since they may lead to economic, social, safety-related and environmental problems. The main difficulty beyond these problems is the poor predictability of the location and characteristics (e.g., size, water flow, sediment filling) of the karst structures. This paper compares the uncertainty of construction time and costs of karst related risks of the karst prediction by the KarstALEA method with the prediction by a purely random karst distribution approach ("Swiss Cheese approach"). The results show that the uncertainty of the KarstALEA method is significant reduced and allows to consider the karst related risk in a more adequate way than with the Swiss Cheese approach. Furthermore, this study shows the crucial role of an adequate karst prediction for the design stage as well as of the exploration activities during excavation to better handle the encountered karst conduits in a save, environmental, economic and durable manner.