| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of mud when drilling bedrock or the like, and containing dust and water deposited at the opening part of a hole from returning back to a hole. SOLUTION: Surface such as bedrock is drilled by a downhole drill for drilling, at the same time compressed air is operated on a part to be drilled, dust being generated by drilling is removed to the outside of a hole 8, and at the same time the hole 8 is dug up to a specific depth under the ground. When the hole 8 is to be drilled, a cylindrical weir 100 that goes around along its opening end by one circle and projects from a ground surface 6 is installed at an opening 7 to the ground surface 6 of the hole 8 for setting so that dust being removed from the hole 8 cannot return back into the hole 8.
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