The European Environment Agency listed 212 fatalities from catastrophic landslides in 1998-2009, which directly resulted in total costs of €551 million. European mountainous regions will face an increased rate of landslide activity due to climate change. Landslides incorporate a wide spectrum of sediment-fluid mixtures between hyper-concentrated flows and dry rockfalls. Landslides are often modelled as granular slides, representing rock avalanches, rockslides and cliff collapses. A granular slide can be defined as a gravity-driven rapid movement of discrete particles assembly consisting of sediment and air, and sometimes also water, relative to its surroundings. This ENSURE project focuses on these granular slides which may cause devastation and human losses in their run-out path.
Well defined and controlled laboratory experiments are often used by researchers to investigate granular slides. However, such experiments have limitations: small-scale laboratory experimental results cannot currently be extrapolated to reliably predict larger-scale natural events. This is due to so-called scale effects resulting in different granular slide characteristics at different geometric scales (sizes). For example, the slide runout distance changes if the slide size is reduced, resulting in a dangerous underestimation. The physical reasons behind scale effects are currently not well understood. A better understanding and quantification of scale effects would enable (i) laboratory experiments to be conducted under conditions where scale effects are negligible or (ii) the removal of scale effects from laboratory experiments in the upscaling process to reliable predict real granular slides in nature. The detailed analysis in a cost-effective manner of the relevance of scale effects in granular slides with a better understanding of the physical processes is therefore a central requirement on the route towards safer mountainous urbanisation and more efficient landslide disaster mitigation strategies in the future.
This project aimed to address these scale effects challenges with the following research objectives (RO):
RO1: To develop a large experimental data base by conducting laboratory granular slide scale series experiments under relevant conditions to understand and quantify scale effects.
RO2: Complementing the work carried out under RO1, develop a fully calibrated and validated numerical simulation model by using CFDEM Coupling to ensure that scale effects are captured and complement the data base with additional slide scenarios.
RO3: Utilising the database compiled in RO1 and RO2, perform an application-based feasibility evaluation to establish a correct upscaling method accounting for scale effects by linking and validating laboratory-scale properties with real field-scale events to ensure the predictive capability of laboratory experiments.
