In Civil Engineering, ground anchors are elements which are actively tensioned to support structures. Due to the active tensioning of the system, anticipated deformations are minimized or entirely eliminated. Fields of applications are either temporary – such as excavation pits and retaining walls – or permanent, e.g. tie backs or masts.
By definition, ground anchors consist of the following three system components:
- Bond length: the anchor is set in the borehole using cement grout (mortar), and is able to transfer the forces to the load-bearing soil via bond and skin friction
- Unbonded (or free) length: the tendon is uncoupled from the borehole wall using a sheathing (sleeve) which is sealed towards the coupling or hollow bar; the unbonded portion can freely extend and tension can be applied to the anchor system
- Anchor head: transfers the anchor force to the substructure (e.g. precast concrete elements) that needs to be anchored Strand or solid bar ground anchor systems are installed into cased, pre-drilled holes and subsequently grouted. DSI ground anchors are installed self-drilling with a pre-mounted sleeve attached to the drill string during installation.