method and device for obturees deplugging sheaths

摘要

A curved conduit 5 in concrete 6 is intended to receive pre-stress cables. It is clogged by a plug 6' of concrete. The problem is to remove the plug 6' without damaging the relatively fragile wall of the conduit 5. This is done in a cycle of three steps. In a first step a chain of articulated shafts 7 convey a rotary drive from a motor 1 to a tool holder including a cutting tool 3. The shafts and the tool holder are guided in the conduit by guide-discs 9 in which they are free to rotate. A short hole of relatively small diameter is drilled in the plug, the length and the diameter being chosen as a function of the curvature of the conduit and its inside diameter to avoid piercing the conduit wall. In a second step the ring of concrete around the hole is blasted away by a jet of water. In a third step the chain is advanced (and lengthened if necessary) and the cycle repeats. IMAGE