Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1993-05-10
1995-06-13
Taylor, Dennis L.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
405258, 4052595, E21D 2002
Patent
active
054236355
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an element for to the preamble of claim 1.
Anchoring elements of this type are used above all in civil engineering for anchoring strands of a ground anchor, having an anchor head which is sunk by a few metres up to some tens of meters in the ground and is anchored there by grouting with a cement compound, at their upper end to the structural part, for example a supporting wall, which is to be held.
A ground anchor of this type essentially comprises a plurality of steel strands having a sheathing, usually made out of an anticorrosion compound and a plastics tube, which steel strands are guided in a closed polyethylene protective tube which, for better anchorage, is ribbed in the region of its lower end and the outer side of which, for better anchorage, is provided in the region of the lower end with circumferential corrugations. The protective tube reaches back into the guide-through duct in the anchoring element and terminates there, while the strands are pulled fully through the guide-through duct and protrude over the opening in the anchoring plate.
The anchor head is grouted by cement being introduced, next to the protective tube, into the borehole and by the region of the borehole situated outside the protective tube being filled in, while the volume enclosed by the protective tube is likewise filled with cement through a hose which is guided in the protective tube and reaches through the guide-through duct up to the surface.
The anchorage of the ground anchor to the structural part is carried out by an anchor bushing being mounted onto the outer surface of the anchoring plate, the anchor bushing having an opening for each strand through which the strand is pulled. The strands are then tensioned while being supported on the anchor bushing, until the desired traction, generally measuring several tons in total, is obtained.
Since the strands have to endure very high traction, it is very important that they should also be protected as far as possible against corrosion in the inaccessible region, in particular in the region of the anchor head. It is known, after the strands have been tightened, to check once again whether the protective tube, critically important for the corrosion protection, is intact, the check being carried out, in fact, by applying a voltage between the strands and earth and measuring the resultant current. Since the protective tube is electrically insulating, whereas the surrounding cement compound and the soil are, even if only slightly, conductive, the measured current provides indication of whether and, if so, to what extent the protective tube is damaged. If the ground anchor is intact, then the guide-through duct is filled at least partially with cement compound and the interspace between the anchoring element and an anchor conduit, which is embedded in the structural part, is also grouted with the same compound.
In the case of known anchoring elements which are made totally from metal, the grouting produces between the strands and earth a short circuit which precludes, furthermore, any check being carried out on the intactness of the protective tube. The effect of this is that any damage to the protective tube which occurs after the completion of the anchorage cannot be detected. As a result, very dangerous situations can arise unnoticed since, if the protective tube is not intact, the strands can corrode and tear off, thereby possibly resulting in the collapse of a supporting wall with consequences such as the after-slippage of earth masses, the collapse of buildings etc.
SUMMARY OF THE INVENTION
The invention is intended to provide a remedy in this regard. The invention provides an anchoring element in which, even after the anchor socket and the anchor conduit have been filled, there is no short circuit present between the strands and earth, thereby enabling the protective tube to be checked at any time, even after the completion of the anchorage. This allows impairments of the corrosion protection to be detected at any time and remedial measures to
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patent: 4592181 (1986-06-01), Matt
patent: 4594827 (1986-06-01), Finsterwalder
patent: 4619088 (1986-10-01), Ripoll Garcia-Mansilla
patent: 5079879 (1992-01-01), Rodriguez
Albrecht-Dessimoz Urs
Keller Roland
Paul Keller Ingenieurburo A.G.
Taylor Dennis L.
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