| 摘要 |
A pile driving rig is used to pre-drill a hole into which an elongate element, such as a pile or a hollow mandrel is inserted. A large portion of the weight of the rig is imposed upon the elongate element by a jack system, one part of which rests upon the pile element and the other part of which jacks up one end of the rig. If further seating of the pile is desired the jacking force is momentarily released so as to drop the superimposed weight of the rig onto the elongate element.
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