Abstract
Fourteen kinds of rock specimen and rock mass were tested to find the main rock mass characteristics affecting the drilling rate of a bit in rotary percussion by 2 hand-type electric and air hammer drills. It was found that the drilling rate of the bit, V (cm/min), consuming constant rotary percussion power of 1050 W could be expressed as functions of the coefficient of crack of rock mass C rmr , the Shore hardness H rms or the amount of Los Angeles abrasion U or the radial compressive strength σ rmt (MPA) of the rock specimen, and the bit diameter D (mm).
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