Simulation of the Blasting Patterns in Shaft Sinking Using a Discrete Element Method

 

Frédéric Victor Donzé

Professor, Laboratoire Sols, Solides, Structures (UMR 5521)
Domaine Universitaire - B.P. 53 - 38041 Grenoble cedex 9 - France
Frédéric.Donze@geo.hmg.inpg.fr 

and

Pascal Bernasconi

YSO Consultants, BP114, 69, Rue de Paris, 91402 Orsay, France
ysoconsultants@yso.fr 

ABSTRACT

Knowing the detonic properties of the explosives used, as well as the mechanical properties of the rock, the goal is to determine the best combinations between the nature of the explosives, the blasting pattern geometry and the blasting firing sequence, in order to be able to extract fragments easily, while limiting if not hindering side damages.

To lead this comparative study between several blasting configurations, numerical simulations using a 3D Discrete Elements Method (DEM) were used. This numerical method was selected because it was possible to get an interesting description of the fracturing and fragmentation of the rocks within a framework of strong dynamic loading.

The results show that in all cases, when the explosives are shot, side damage is induced in the model, in addition to the damage related to the quasi-static deconfinement. The results also show that the most favorable blasting configuration, when requiring a weak extension of the damage in the rock mass, while sufficiently splitting up the background shaft area to be extracted, corresponds to blasting charges with a sufficient time delay firing sequence with the use of softened loads using Nitram and Nitralex-type emulsions. The worst case corresponds to the standard blasting configuration (detonating cord and dynamite) where all explosions occur simultaneously. The side damage becomes considerable then and can harm the stability of the shaft. 

This case study shows how the use of a discrete element analysis can help to optmize the blasting process in the mining industry. 

Keywords: DEM, discrete elements, distinct elements, numerical modeling, blasting, dynamic loading, shaft sinking.

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