Laboratory and numerical investigation into the characteristics of rock fragmentation

Abstract Optimisation of the efficiency of crushers is desirable in terms of reducing energy consumption, increasing throughput and producing better downstream performance as a result of improved size specification. The mechanism of rock fragmentation within crushers is dominated by compression at high strain rates. Research presented in this paper has investigated the relationship between strain rate, impact energy, the degree of fragmentation and energy efficiencies of fragmentation. For the investigation two laboratory test methods were used to generate compressive failure under different strain rates. The tests were namely a variable speed unconfined compressive strength test, and a laboratory drop weight test. Laboratory testing and computer simulations showed that a greater amount of energy was required for breakage with increasing strain rate and also samples broken at higher strain rates tended to produce a greater degree of fragmentation. It was also observed that not only the impact energy influences the degree of fragmentation but the combination of drop weight/height also has an effect.

[1]  P. A. Cundall,et al.  A DISCONTINUOUS FUTURE FOR NUMERICAL MODELLING IN GEOMECHANICS , 2001 .

[2]  S. Morrell,et al.  Mineral comminution circuits: their operation and optimisation , 1996 .

[3]  Fumio Saito,et al.  Mechanical Properties of Brittle Materials and Their Single Fracture under Dynamic Loading , 1973 .

[4]  Luís Marcelo Tavares,et al.  Optimum routes for particle breakage by impact , 2004 .

[5]  G. McDowell,et al.  Discrete element modelling of cyclic loading of crushable aggreates , 2003 .

[6]  C. M. Sangha,et al.  Influence of time on the strength, deformation and fracture properties of a lower devonian sandstone , 1972 .

[7]  Douglas W. Fuerstenau,et al.  The energy efficiency of ball milling in comminution , 2002 .

[8]  E. T. Brown,et al.  Underground excavations in rock , 1980 .

[9]  Alexander V. Potapov,et al.  Making a Discrete Grain Breakage model practical for comminution equipment performance simulation , 2004 .

[10]  Hongyuan Liu,et al.  Numerical investigation of particle breakage as applied to mechanical crushing Part I: Single-particle breakage , 2001 .

[11]  Mojtaba Ghadiri,et al.  Distinct element analysis of bulk crushing: effect of particle properties and loading rate , 2000 .

[12]  E. T. Brown.  Rock characterization, testing & monitoring: ISRM suggested methods , 1981 .

[13]  Luís Marcelo Tavares,et al.  Particle weakening in high-pressure roll grinding , 2005 .

[14]  L. M. Tavares,et al.  Single-particle fracture under impact loading , 1998 .

[15]  Idar Larsen,et al.  Comparison between controlled laboratory experiments and discrete particle simulations of the mechanical behaviour of rock , 2005 .

[16]  B. N. Whittaker,et al.  Rock Fracture Mechanics: Principles, Design and Applications , 1992 .

[17]  P. Cundall,et al.  A bonded-particle model for rock , 2004 .

[18]  D. Grady,et al.  Strain-rate dependent fracture initiation , 1980 .

[19]  Alexander V. Potapov,et al.  Computer simulation of impact-induced particle breakage , 1994 .

[20]  D. Whittles,et al.  Numerical simulation of the dynamic impact breakage testing of rock , 2005 .

[21]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .