| 摘要 |
PROBLEM TO BE SOLVED: To provide a material for drilling a hole in natural ground, enabling to easily and rapidly drain water in the natural ground within a drilling area in front of the working face of a tunnel without using special machines, and to provide a draining method using the material. SOLUTION: A material for drilling a hole in natural ground comprises rods 21-23 each having a cavity 25 therein and inserted into sheath pipes 11-13, the sets of plural rods 21-23 and sheath pipes 11-13 connected together to extend the material. A drilling bit 28 is mounted at least on the end of the leading rod 11, and a striking force is applied as the bit 28 is rotated, with water ejected through the cavities 25 in the rods 21-23 to drill a hole in the natural ground. The plurality of sheath pipes 11-13 are constructed of synthetic resin pipes 12, 13 except the leading pipe 11 and some parts such as pipe fittings 19a, 19b. After the hole is drilled in the natural ground by use of the material, the rods 21-23 are pulled out of the sheath pipes 11-13 and recycled and water is drained through the insides of the sheath pipes 11-13 left behind in the hole drilled. The sheath pipes 11-13 are left behind in the drilled hole even after the draining operation has been finished.
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