岩石の打撃さく孔に関する研究 (第2報)

抄録

The percussion drilling tests of mine rocks by the drop hammer type drilling test machine were concluded in this second report.
This report includes:
1) parallel two blows test,
2) cross two blows test,
3) multiple blows test.
The parallel two blows test and the cross blows test were to measure dimensions, i. e. volume, plane area, depth, width, etc., of a compound notch made by adding the next pecussion blow of bit parallel-placed or cross-placed to the former single blow notch on a rock surface. In the multiple blows test, a measurement of the depth of the drilling hole made by multiple percussion blows of bit with a constant rotation angle of a bit was carried out.
Aims of those tests were to find the most suitable distance between parallel two blows to get larger notches, the most suitable cross angle of cross two blows and the most suitable rotation angle of bit for percussion drilling.
On those tests, the most suitable values for granite were showed as follows:
The most suitable distance was 0.65cm on 2m-kg blow energy. 0.90cm on 4m-kg blow energy, 1.15cm on 6m-kg blow energy.
The most suitable cross angle was 20° on 2m-kg blow energy, 24° on 3m-kg blow energy, 28° on 4m-kg blow energy, 28° on 6m-kg blow energy.
The most suitable rotation angle of bit was 24°-34° and there is a tendency to increase with a blow energy.