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Dynamic behaviour and fragmentation of quasi-brittle materials: application to rock fragmentation by blasting

Ahmed Rouabhi
Abstract : This thesis seeks to find a computational methodology to simulate both the behaviour and the fragmentation of quasi-brittle materials, such as rocks and concrete, under dynamic loading. Such a methodology will help to a better understanding of the explosive rock breakage mechanisms and, as consequence, will contribute in the optimization of blasting performances. In this study, we consider that the fragmentation process is a natural extension of the fracture process. In order to describe the dynamic fracture process, a suitable phenomenological constitutive model is developed and implemented in a finite element code. As for the dynamic fragmentation, it is treated by a post processing analysis based on the history of the material's thermodynamic state. To reproduce the macroscopic behaviour of quasi-brittle materials including load-induced anisotropy due to cracking, the internal variables method based on continuum thermodynamics is used. A scalar internal variable is introduced to model, at the macroscopic level, the strain softening under compressive loadings. Under tensile loadings, a second-order symetric tensor is used to describe the essential features of the induced anisotropic damage. Under complex loadings, these two models are coupled and the crack closing-reopening effect is also treated. The integration of the developed model in the finite element code VIPLEF3D has led to the development of a relaxation method characterized by an explicit updating of the state variables. Concerning the dynamic fragmentation, from laboratory blastings tests, a general formulation of predicting the fragment size distribution is provided. In this formulation, a mean fragment is linked to mechanical quantity, wich is assumed to be the origin of the fragmentation process, by an intrinsic function wich can be identified by using suitable laboratory fragmentation tests. This mechanical quantity is given by the resolution of the initial boundary-Value Problem where the developed constitutive model is considered. Finally, the complete approach is then applied to the modelling of the fracture and the fragmentation of chamber blasting tests of cylindrical rock materials samples
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https://pastel.archives-ouvertes.fr/pastel-00001084
Contributor : Ecole Mines Paristech <>
Submitted on : Monday, February 28, 2005 - 8:00:00 AM
Last modification on : Friday, March 8, 2019 - 8:52:03 AM
Long-term archiving on: : Thursday, September 30, 2010 - 6:30:33 PM

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  • HAL Id : pastel-00001084, version 1

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Ahmed Rouabhi. Dynamic behaviour and fragmentation of quasi-brittle materials: application to rock fragmentation by blasting. Sciences of the Universe [physics]. École Nationale Supérieure des Mines de Paris, 2004. English. ⟨pastel-00001084⟩

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