| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of partially expanding inside of borehole by which a step part can be formed in a borehole formed in a prescribed borehole forming direction from the surface of a rock mass by expandably drilling the rock mass in part of the borehole, and to provide a rock drilling head and a rock drill which are suitable for the method. SOLUTION: In the method of partially expanding inside of borehole, a rod 4 and the main body 6 and front-end member 24 of the rock drilling head 2 are integrally fed in the borehole forming direction (+X) by applying a rotary striking force to the head 2. As the rod 4, main body 6, and front-end member 24 are fed, the mobile members 14 and 16 of the head 2 move and are separated from each other in the radial direction around the center axis of the borehole 8 and a rock drilling bit 18 comes into contact with the internal surface of the borehole 8 and starts drilling at the forming position of the step part. As the rod 4, main body 6, and front-end member 24 are fed more, the mobile members 14 and 16 move and are further separated from each other in the radial direction around the center axis of the borehole 8 while drilling the internal surface of the borehole 8. Consequently, the diameter of the borehole 8 is enlarged and the step part is formed.
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