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Bertrand François

Oumar Keita


The optimization of the blocometry of a shooting with explosive in mines and quarries are a major factor for this type of operation because the performance depends on it. The ideal blocometry avoids the very small and very large blocks. Very small blocks, similar to dust, have a low valuation. Similarly, the block size of one meter cube are difficult to transport and do not pass through the crusher. They should therefore be decomposed using a hydraulic rock breaker which increases operating costs. To better control the mass distribution, blast design should be improved. However the techniques of shooting in career and mines are mainly heuristic and based on empirical concepts. In this context, the study of fragmentation under dynamic stress is a way to optimize blocometry. It is within this context that this thesis takes place. The objective is to develop a dynamics damage model of rock using the method of asymptotic homogenization [1], [2] in order to optimize fragment size block.

This thesis aims to develop a model with double scales (Figure) of dynamics damage of rock using the asymptotic homogenization method. The results of this modeling would make it possible to obtain the macroscopic behavior of damage through the observation on a microscopic scale and subsequently to identify the parameters influencing the fragments size.




To achieve the desired results, we propose the following methodology

-A multi-scale modeling of damage and fracture in the rock dynamics framework

- Implementation of the model in a finite element code to numerically model perform the considered boundary value problem (excavation by rock blasting)

-Validation of the model by experimental tests. These experimental studies will be conducted on rock samples extracted at the site of the Bauxite Company of Guinea (CBG). These tests will highlight the various failure modes and damage of rock sample under dynamic loads

Selected publications [1]. Dascalu C., François B., Keita O. (2010). A two-scale model for subcritical damage propagation. International Journal of Solids and Structures 47(3-4): 493-502.

[2]. François B., Dascalu C. (2010). A two-scale time-dependent damage model based on non-planar growth of micro-cracks. Journal of Mechanics and Physics of Solids. 58(11): 1928-1946.