| 摘要 |
PROBLEM TO BE SOLVED: To create sand piles having the quality equal to or better than the conventional ones in a shorter period of time and at a low cost by restricting the influence of vibrations to nearby houses without decreasing vibration energy of a vibrohammer used during sand pile formation. SOLUTION: A sand pipe creating hollow pipe 1 is split vertically at the center into two pieces, and both of them are jointed with a flexible material 2 such as rubber and assembled to the previous hollow pipe 1. Vibrohammers 3a, 3b having the same output are installed to the head of respective half-divided pipe body potion; when one vibrohammer 3a is generating vibration downward, other vibrohammer 3b generates the vibration upward by mechanical or electrical synchronization. In this way, nearby ground receives vibrations reversely upward and downward at the same time, so that the vibration waves having different phases are interfered and canceled each other so that damages by the vibrations to the nearby area can be eliminated.
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