| 摘要 |
The invention relates to a device comprising a solid element and means enabling the said element to be lifted and then released. In accordance with the invention, the solid element comprises a slab 3 which may slide freely in a frame, and the lifting means comprise means 5 for driving by friction on one side of the slab and bearing means 6 on the other side of the slab, these bearing means being movable between an active lifting position and a passive position in which the said slab is released so as to fall freely. Application in particular to the breaking or cracking of the pavement of motorways, airport runways or parking areas. <IMAGE>
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