Anticipating an imminent large rock slope failure at the Hochvogel (Allgäu Alps)

Costs for installation and maintenance of protective structures are increasing while alpine hazards progressively threaten alpine communities, infrastructure and economics. Thus, reliable process-based anticipation and early warning strategies offer a cost-effective and smart solution for alpine societies in the near future. However, only few comprehensive pre-failure observations of alpine rock slopes have been reported so far. This paper demonstrates pre-failure observations of a rapidly deforming rock mass (potentially 260,000 m³) at the Hochvogel (Allgäu Alps, 2,592 m a.s.l.) and a geotechnical monitoring and warning concept. This is implemented in the complementary multi-method approach of the AlpSenseBench project and the basis for an effective and reliable early warning system. Since 2014, overall displacement rates in the range of 2 to 10 mm/month in the main decametre deep fracture are observed. It is expected that predictive acceleration patterns will appear in the final pre-failure stage. A detailed knowledge of multiple anticipative signals in correlation with accelerating rock slope deformations will contribute to an advance in accuracy and reliability of rock slide early warning.