14. Proof Testing of Cable Anchors in Rockfall Protection Systems

摘要

This is a report on the testing procedures for wire rope anchors we see in rockfall mitigation systems across the US. For years the standard had been to incrementally load wire rope anchors just as if they were solid bar anchors. Wire rope anchors react differently to loading as compared to solid bar anchors. The cable has a certain amount of natural elongation due to their construction that takes place under loading. They are superior to solid bar anchors in rockfall systems as the wire rope anchor has the ability to absorb rock impacts without the possibility of breaking due to shearing. Due to this natural elongation, the incremental loading procedures we typically see in specifications for rockfall barriers and rockfall drapery projects are not necessary and have no relevance in determining the ultimate strength and pullout capacity of the anchor. We have found that simply just loading the anchor to the capacity required, waiting a couple of minutes for the natural elongation to take place and then reloading the wire rope anchor to the required capacity and holding at that load for a designated period of time proves the capacity of the anchor without the loading and unloading several times that is required during incremental loading procedures.