Rock anchors are post-tensioned tendons installed in drilled holes for which at least the entire bond length is located in rock. The anchor force is transmitted to the rock by bond between the grout body and the rock. Rock anchors can remain unbonded in the free stressing length allowing the anchor to be checked and re-tensioned at any time. In such cases, adequate corrosion protection for the stressing anchorage and the free stressing length must be provided.
On the other hand, the free stressing length can also be fully grouted after the anchor has been stressed, in which case future load adjustment is no longer possible.