ESR8 Lorenzo Benedetti

Research project description

Mixed formulations for damage and plasticity in landslide and debris flow initiation

 Fellow:                   Lorenzo Benedetti

Department:           International Centre of Numerical Methods in Engineering – CIMNE Universitat Politecnica de Catalunya, Barcelona

Supervisor:            Prof. Miguel Cervera, Prof. Michele Chiumenti, Prof. Eugenio Onate

Debris flows are a mixture of soil, rock boulders and water, descending throughout mountainous channels at very high speeds. Frequently, debris flows are triggered by landslides in which the mobilized soil appears to be partially or completely fluidized. Determining the volume of detached soil is vital for the forecast and the predisposition of proper countermeasures. As one can easily understand, the mass of mobilized material is directly related with the momentum of the debris flow and, consequently, with the level of hazard. Then, an extensive understanding of the initiation phenomenon and its fluidization is required for an adequate characterization of the subsequent motion.

The aim of the research is the creation of a unified model for landslides and debris flow initiation in the framework of the mixed finite element method. Significant emphasis is given to some particular aspects. First of all, the focus will be on the creation of a numerical tool capable of identifying slip lines due to damage and plasticity. Mathematical insights of the problem are given in order to tailor a general formulation. An example of some preliminary results is shown in Figure 1. Secondly, the capabilities of methodologies above introduced are benchmarked in a geotechnical context. On one hand, the implementation of simple stress-strain relations -like Drucker Prager, Von Mises, Rankine- allows to study the convergence of the numerical model. On the other hand, the introduction of more realistic constitutive equations is essential in order to obtain meaningful results to be compared with real cases. In the light of these arguments, collaborations with ESR Evanthia Kakogiannou, Maria Lazari and Vasileios Matziaris will be an opportunity to directly validate the model.

Moreover, the partnership with Bundesforschungs - und Ausbildungszentrum fur Wald, Naturgefahren und Landschaft Federal Institute in Innsbruck (Austria) will become a further opportunity to apply the studied numerical tools to various case studies. As a matter of fact, mechanical failure of snow layers represents a simpler case of landslide. In a very simplistic analysis of the issue, one can imagine the single snow phase as an almost homogeneous material which mechanical characteristics are given by the compaction properties and the temperature effects. According to this reason, the possibility of coupling the mechanical model with hydro­geological (concerning landslide initiation) or temperature (in the specific case of avalanche initiation) is explored. Finally, to complete the work, a numerical method to describe the fluidization and phase change of detached volume is studied as last part of the research.

Many of the proposed topics are the back bone of the WP3 and they will require a constant dialogue with the other ESR Alessandro Leonardi, Pablo Becker and Xiannan Meng .

 ESR8 Lorenzo Benedetti

Figure 1. Failure of a slope under the imposed displacement of a foundation. Right figure: Displacement field. Left figure: Equivalent Plastic Strain field.


ESR8 Lorenzo Benedetti