Analyzing the Sensitivity of a Distinct Element Slope Stability Model: A Case Study on the Influence of Permafrost Degradation on Infrastructure Stability

Since the 19th century, the warming rate in the European Alpine region has been twice as high as the average global rate. Warming-related permafrost degradation has been shown to cause a reduction of bedrock bearing capacities, potentially leading to the destabilization and eventually to the failure of high-alpine infrastructure. The presented study investigates permafrost-related changes of bedrock properties and their stability-relevant effects on high-alpine infrastructures. The Kitzsteinhorn summit and its highly frequented cable car station (3029 m a.s.l., Austria) is home to the interdisciplinary Open Air Lab Kitzsteinhorn (OpAL), where the consequences of climate change, based on a long-term monitoring of surface, subsurface and atmospheric parameters are investigated. In a rock-ice mechanical model, degradation of permafrost causes changes in rock fracture toughness and rock friction, affects ice fracturing and creep as well as the behavior of rock-ice interfaces. A first numerical distinct element model of the mechanical behavior of rock slope and the infrastructure was set up, based on OpAL datasets and a civil engineering assessment of the cable car setup. By conducting a thorough rock mechanical model sensitivity analysis, it was tested how individual model parameters affect the rock slope stability below the cable car summit station. The accurate knowledge of the most sensitive parameters and their empirical variation range generates a better process understanding of destabilisation in permafrost-affected rock walls. This facilitates efficient stabilization measures for affected high-alpine infrastructures. Here we show, that the stability of infrastructure on permafrost-affected bedrock is not only passively determined by mechanical changes in the underlying frozen rock mass, but infrastructure also actively affects thermal conditions and rock stability in a relevant way.