ROTATIONAL-PERCUSSIVE DRILLING (EN: rotary-percussion drilling; DE: Drehschlagbohren; FR: forage rotopercutant; ES: sondeo por rotacion-percusion; RU: вращательно-ударное бурение) is the process of the breaking of the rock during the drilling of the blastholes and boreholes, using the permanently rotating drilling tool, which is pressed into the stope with the great axial thrust, upon which there are periodically inflicted the blows by the striker.
The first machines for the rotational-percussive drilling of the blastholes have been developed within the West Germany during the end of the 40-ies. The rotational-percussive drilling is performed using the drill carriages, onto which they install the powerful hammer drills, which are equipped with the hydraulic manipulators with the chain-type and screw-type advancers, and also using the mobile drilling installations with the chassis on the pneumatic tires or caterpillar tracks. The rock-breaking tool (see the Figure) for the rotational-percussive drilling is the drill crowns with the cutting hard-alloy blades with the frontal negative angle, which are connected using the couplings with the round steel rods, which have the central flushing channel, with the screw thread of the rope, stop, or round-stop profile. In case of the rotational-percussive drilling, they rigidly install the drill carriage into the stope with the help of the jackscrews of the strut type, and the hammer drill is fixated using the manipulator and advancer along the axis of the drilling for the blasthole or borehole, later there is enabled the rotator, the flushing liquid is delivered into the stope, the axial th rust is created by the advancer, and after the contact of the tool with the stope, there is enabled the percussive mechanism of the pneumatic or hydraulic hammer drill. The frequency of the rotation of the tool during the rotational-percussive drilling is up to 300 revolutions per minute, the axial thrust is up to 14 kilonewtons, the frequency of the blows is 2000-4000 per minute, the energy of the single blow is 20-40 joules per 1 centimetre of the diameter of the tool. The net speed of the rotational-percussive drilling is 1-2 metres per minute, which is significantly faster, than the speed of the usual hammer drill.
The rotational-percussive drilling is used for the drilling of the blastholes during the conducting of the underground mine workings, and for the drilling of the boreholes during the underground breaking of the strong ores, and of the ores with the medium strength, and within the hydraulic-technical and road construction.
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