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Investigation of rock fragmentation during rockfalls and rock avalanches via 3-D discrete element analyses

Lookup NU author(s): Professor Stefano Utili

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Abstract

This paper investigates the characteristics of dynamic rock fragmentation and its influence onthe postfailure fragment trajectory. A series of numerical simulations by discrete element method (DEM)were performed for a simple rock block and slope geometry, where a particle agglomerate of prismatic shapeis released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point.The rock block is modeled as an assembly of bonded spherical particles with fragmentation arising from bondbreakages. Bond strength and stiffness were calibrated against available experimental data. We analyzedhow dynamic fragmentation occurs at impact, together with the generated fragment size distributions andconsequently their runout for different slope topographies. It emerges that after impact, the verticalmomentum of the granular system decreases sharply to nil, while the horizontal momentum increasessuddenly and then decreases. The sudden boost of horizontal momentum can effectively facilitate thetransport of fragments along the bottom floor. The rock fragmentation intensity is associated with the inputenergy and increases quickly with the slope angle. Gentle slopes normally lead to long spreading distanceand large fragments, while steep slopes lead to high momentum boosts and impact forces, with efficient rockfragmentation and fine deposits. The fragment size decreases, while the fracture stress and fragment numberboth increase with the impact loading strain rate, supporting the experimental observations. The fragmentsize distributions can be well fitted by the Weibull’s distribution function.


Publication metadata

Author(s): Zhao T, Crosta GB, Utili S, De Blasio FV

Publication type: Article

Publication status: Published

Journal: Journal of Geophysical Research: Earth Surface

Year: 2017

Volume: 122

Issue: 3

Pages: 678-695

Online publication date: 06/03/2017

Acceptance date: 02/03/2017

Date deposited: 22/04/2017

ISSN (print): 2169-9003

ISSN (electronic): 2169-9011

Publisher: Wiley-Blackwell

URL: https://doi.org/10.1002/2016JF004060

DOI: 10.1002/2016JF004060


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