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The Effect of Strain Rate on the Breakage Behaviour of Rock |
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The Effect of Strain Rate on the Breakage Behaviour of Rock Authors: K. Jackson, S.W. Kingman, D.N. Whittles, I.S. Lowndes, D.J. Reddish
For the optimum design of a rock crushing plant the breakage characteristics of the rock under the
loading conditions imposed by the crusher are required. Often the determined static mechanical values
fail to characterise the energy required and degree of fragmentation of the material within the crusher.
This paper describes a laboratory and numerical investigation into the affect of strain rate on the energy
requirements and breakage characteristics of three different sedimentary rocks. For each rock type high
speed uniaxial compression tests were carried out at six different strain rates over the range 2.57 × 10–5
strain/s to 0.02 strain/s. Changes in the stress-strain behaviour were discovered indicating the importance
of strain rate on breakage characteristics. For each of the rock types the stress/strain curves showed an
increase in ductility as the strain rate increased and it was calculated that the energy used in bringing the
specimen to fracture increased by up to 50%. The increase in energy was also accompanied by an increase
in the degree of fragmentation achieved. The numerical modelling of the high speed compression test
was undertaken for the sandstone using the discrete element method code PFC3D produced by Itasca.
The numerical modelling reproduced the increase in energy requirements for fracture and an increase in
the degree of fragmentation. The modelling also predicted that this trend would continue at strain rates
of 1 strain/s that would be anticipated in rock crushers. |
2011