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ORE PREPARATION
Название Crack propagation in rock upon impact
DOI 10.17580/or.2019.06.01
Автор Bolobov V. I., Le-Thanh B., Plaschinsky V. A.
Информация об авторе

St. Petersburg Mining University (St. Petersburg, Russia):

Bolobov V. I., Professor, Doctor of Engineering Sciences, Senior Researcher, boloboff@mail.ru
Plaschinsky A. A., Postgraduate, SlavaPlash@yandex.ru

Vinacomin – Institute of Energy & Mining Mechanical Engineering (IEMM) (Hanoi, Vietnam):

Le-Thanh B., Senior Researcher

Реферат

Based on the assumption that destruction of a rock fragment upon impact is conditioned upon the achievement by the emerging crack of any of the free surfaces of the fragment, the propagation velocity of a fracture crack vcr was estimated experimentally and by calculation using granite samples of the Vyborg massif. In the experimental setup, impacts at various points on the horizontal surface of granite fragments enabled establishing the most effective impact distance h = leff from the edge of their lateral surface, at which the impact breaks off the largest piece of rock. The dependence of this value on the diameter d of the flat face of the ram tester was established; an analysis of the shapes of the resulting broken-off fragments indicated mutual proximity of the values of their geometric parameters; their dependence on d and the length of the fracture crack lcr were established by calculating the arithmetic mean of these parameters. Such single impact indicators as the rock resistance force Nm, contact stress σc, penetration αp of the ram tester into the rock, and impact duration tm, were calculated; their dependence on d was established. The calculated values of tm were used to calculate the fracture crack propagation velocity vcr. The latter is close to 11 m/s for all granite fragments, regardless of the values of d and tm, which is significantly lower than the values established in other studies. This is due to significant differences in the medium being fractured and in the impact velocity.

Ключевые слова Ram tester penetration, granite fragments, load characteristics, chipped piece parameters, crack propagation velocity
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