On the Chipping Strength of Coal Measures Rocks

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  • 夾炭層岩石の抗砕力について
  • キョウタンソウ ガンセキ ノ コウサイリョク ニ ツイテ
  • 抗碎力と破砕特性との関連性
  • Relation between chipping strength and fracturing characteristics

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The authors analysed fracturing characteristics in rocks by the percussion drilling of coal-measures rocks from 21 coal mines in Japan, and they investigated an index that determines the volume of cuttings on the fracturing tests by the pendulum hammer type test machine.<BR>The stress waves are measured by means of wire strain gauge on the midway of long rod when the rocks were struck by standard bit and carried out, the chipping resistance in relation to the waves of incidence and reflection.<BR>On the surface of rock specimens the individual and multiple percussion blows were performed under various conditions. The weight of cuttings is given as follows:W=ηθ/4D{h(kv-F0)}α where W: weight of cuttings on the multiple blows, θ: angle of rotation, D: diameter of the fracturing hole, ν: velocity of blow, F0: critical energy of blow, ρ: specific density of rock, h: coefficient of crater depth, η: correct coefficient of the fracturing depth, α: correct index of the fracturing depthk: unit chipping strength<BR>From the above, it was found that the fracturing characteristics in rocks were not experimentally defined without several indexes besides a unit chipping strength.

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