Fractal characteristics of rock fragmentation under impact load

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Journal of Vibration and Shock ›› 2020, Vol. 39 ›› Issue (13) : 176-183.

JI Jiejie1,2, LI Hongtao1,2, WU Faming3， YAO Qiang1,2

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Abstract

In order to study fractal characteristics of rock fragmentation under impact load, rock dynamic tests with separated Hopkinson pressure bar (SHPB) were conducted for granite and sandstone to obtain rock stress-strain curves, broken characteristics, strength parameters and energy ones under different strain rates. The standard sieve was used to screen and classify broken rocks to gain rock fragmentation distribution curves. The fractal dimension D was calculated based on the mass fractal model of fragments’ particle size distribution. Finally, relations among fractal dimension, loading parameters, broken characteristics and energy-dissipating were analyzed. The results showed that the fragmentation distribution of rock under impact load accords with the fractal law; rock dynamic compressive strength increases with increase in strain rate, both of them satisfy a power function relation; the greater the rock strain rate during loading, the deeper the degree of rock fragmentation and the larger the fractal dimension; the relation between fractal dimension and rock fragmentation energy- dissipating density satisfies a power function relation; fractal dimension can be used to realize quantitatively studies among rock broken characteristics, mechanical properties and energy-dissipating characteristics under impact loading.

Key words

impact load / fractal dimension / fracture morphology / dynamic mechanical properties / energy absorption

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JI Jiejie1,2, LI Hongtao1,2, WU Faming3， YAO Qiang1,2. Fractal characteristics of rock fragmentation under impact load[J]. Journal of Vibration and Shock, 2020, 39(13): 176-183

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