Mass-waste modeling across scales
Marie Skłodowska-Curie Individual Fellowship
Mass-wasting is the general term for the transfer of Earth material down hillslopes. It includes six main categories1 : falls, topples, slides, spreads, flow and
slope deformation2,3,4. Some examples are rockfalls, debris flows, ice avalanches or soil creep. Not only do such events sculpt the local topography but in many cases they pose as natural hazards, having significant economic impact or by seriously endangering human lives. As an example, a thorough study conducted by D. Petley5 reports on a number of 2620 fatal (nonseismic) landslide events between 2004 and 2010 worldwide, with altogether ca. 32000 casualties. Furthermore this dataset (and usually other available datasets) only account for extreme events (e.g. with fatalities), by including smaller scale, local or unreported events, the actual number of landslides may be much larger with an unpredictable number of affected people and infrastructure. This highlights the fact that research done on mass-waste events is not only important from the scientific point of view as a geomorphological influence, but in many cases also for better future predictions, preventive measures and natural hazard risk assessments. Its importance is for example also reflected in the EU Horizon 2020’s third pillar “Societal challenges” sub-programme: “Climate action, environment, resource efficiency, and raw materials”6.
One very important tool in today’s mass-wasting and natural hazard research7 are numerical models. The rapid development of computational power in the 21 st century has lead to these tools being used for both prediction, risk assessment and to get a better understanding on the underlying physical phenomena. However numerical models usually have a certain length scale where they work, and one very powerful and genuine methodology on the road of developing better models is when one connects models working on different length-scales in order to get a more complete picture. This approach will be the method of choice of the project.
The basic objective of the project is to develop a discrete element model (DiEM) based numerical environment (called: MWDiEM), that is able to effectively model the dynamics of cohesionless, polyhedral or spherical granular particles. These shapes are anticipated to realistically model a number of particle types found in real mass-waste events (e.g. rocks). In DiEM the trajectory of each particle is followed individually. By connecting this particle-scale model to the two-phase continuum flow model based, realistic scale mass-flow simulation tool r.avaflow8 one will bring together the full power of a Lagrangian and an Eulerian method. Such a framework will not only be a useful addition to any natural hazard research toolbox, but will have significant importance to the granular physicist and engineering communities as well, bringing interdisciplinary research to the forefront.
A mass-waste event may consist of a fluid phase and a solid, granular phase. For example debris flows may contain a significant amount of water, while rock-slides may have no or negligible interstitial fluid. By default DiEMs only account for the granular phase, thus the code developed in the current project will be able to handle mass-wasting phenomena where the fluid content is none or negligible, e.g. dry rock avalanches, boulder falls, dry sand, gravel and debris slides or dry debris flows. However as a future continuation of the project MWDiEM will be further developed in order to account for the fluid phase as well. This also establishes the choice for the large scale continuum model, r.avaflow, as this unique and very general tool will guarantee that once the fluid phase is also added to MWDiEM, the connection between the two software will be directly and in a straightforward manner possible, completing the numerical picture a step even further.
The main objectives of the project:
- Develop an efficient, open-source 3D discrete element model based software called: MWDiEM, that can model realistic particle shapes found in dry or mostly dry mass-waste events and make this code ready for application to real-world natural hazard events (within efficiency and model limitations).
- Validate the developed code by comparing its results to laboratory experiments and real-world case studies. Connect MWDiEM with the two-phase continuum model based software r.avaflow in order to create a framework that makes modelling across scales possible.
- Apply this framework along with experiments to investigate the importance of segregation on dry mass-flow9 dynamics and runout zone geometry.
- Determine possible future fundamental research and development directions and engineering applications for both the framework and MWDiEM.
- Note, that in the project mass-wasting is categorized according to the classification proposed by Hungr et al.2 based on the works of Varnes3,4.
- O. Hungr, S. Leroueil, L. Picarelli, Landslides 11 (2), pp. 167-194 (2014)
- D. J. Varnes, Landslides, analysis and control 176, Transportation Research Board, pp. 11–33 (1978)
- D. M. Cruden, D. J. Varnes, Landslides investigation and mitigation. 247. Transp. Res. Board, pp. 36–37 (1996)
- D. Petley, Geology 40 (10), pp. 927-930 (2012)
- V. Gallina, S. Torresan, A. Critto, A. Sperotto, T. Glade, A. Marcomini, Journal of Environmental Management 168, pp. 123-132 (2016)
- M. Mergili, J. Fischer, J. Krenn, S. P. Pudasaini, submitted to Geosci. Model Dev., www.avaflow.org (2016)
- The word “flow” is used as defined in Ref. 2.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 743713.