Numerical investigation of snow mechanical behaviour : a microstructural perspective

Abstract : Dry slab snow avalanches represent a major natural hazard that is extremely difficult to manage. Attempts to model this phenomenon are hindered by the lack of a constitutive law that would describe the mechanical behaviour of snow on a material scale. In particular, relatively little is known on the failure and post-failure response of snow at high loading-rates. The highly fragile nature of the material in this deformation regimerenders experimental investigation difficult and complicates observation at the microstructural level.As an alternative to experiments, a Discrete Element Method-based numerical model of snow is developed in this thesis. The model enables us to simulate the response of snow to mechanical loading, while accounting for actual snow microstructure by using X-ray attenuation images of snow microstructure as input. Snow is considered as a cohesive granular material and an original methodology is developed in order to model the shape of each grain. Individual grains are bound into the snow matrix by modelling cohesion between neighbouring grains.The model is then used to explore the macroscopic mechanical response of different snow samples to mixed-mode loading. Three typical modes of failure are observed in all tested snow samples, depending on the level of applied normal stress: a localized shear failure at low normal stress (mode A), a shear failure-induced volumetric collapse at intermediate levels of normal stress (mode B), and a normal failure and collapse for high values of normal stress (mode C). The observed failure modes result in closed failure envelopes and no qualitative difference is observed between the mechanical responses of different snow types.The internal mechanisms that lead to volumetric collapse are further examined on the microscale. Force chain buckling is identified as a trigger of this material instability. Additionally, force chain stability appears to be controlled by the contacts between the force chain members and the surrounding grains. The failure in these contacts, which is evidenced in modes B and C, allows force chain buckling to develop and results in subsequent volumetric collapse.
Document type :
Theses
Complete list of metadatas

Cited literature [151 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-02159398
Contributor : Abes Star <>
Submitted on : Tuesday, June 18, 2019 - 5:10:39 PM
Last modification on : Wednesday, November 6, 2019 - 3:28:58 AM

File

MEDE_2019_archivage.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-02159398, version 1

Collections

Citation

Tijan Mede. Numerical investigation of snow mechanical behaviour : a microstructural perspective. Earth Sciences. Université Grenoble Alpes, 2019. English. ⟨NNT : 2019GREAU004⟩. ⟨tel-02159398⟩

Share

Metrics

Record views

62

Files downloads

38