A ground anchor generally consists of a steel tendon (bar or strands) that is grouted into a pre-drilled hole in rock or soil. After the grout cures, the tendon is pulled into tension against a plate or block and is locked in place to resist movement of a retaining structure. These rock anchors or soil anchors are also referred to as “tiebacks”.
The basic components of a ground anchor are the: (1) bond length; (2) free stressing length; and (3) anchor head. The bond length, also called the “socket”, is that part of the anchor that transfers the tensile load from the steel tendon into the surrounding rock or soil. The anchor tendon is typically grouted into the bond length with a cement grout. The free stressing length is unbonded and is designed to stretch and transfer load from the grouted socket to the anchor head. The anchor head connects the anchor tendon to the structure being loaded and typically includes a nut and bearing plate.
Soil anchors and rock anchors provide a high load capacity even in poor ground conditions, as the bond length can simply be increased to accommodate the load required. Anchors do not involve the large excavation areas required by alternative methods and are a particularly attractive option when space is limited and when low impact or the environment is a priority. Because anchors can be constructed of durable anticorrosive materials, they offer a permanent system with little or no maintenance.
Anchors are often used for excavation support, or as a part of permanent retaining walls, or to resist up-lift forces on foundations. Rembco uses rock anchors to stabilize slopes and walls, provide tiebacks for bridges and towers, to stabilize dams, and to secure caisson bottoms.