Tie Back Anchoring
A tieback is a horizontal wire or rod, or a helical anchor used to reinforce retaining walls for stability. With one end of the tieback secured to the wall, the other end is anchored to a stable structure, such as a concrete deadman which has been driven into the ground or anchored into earth with sufficient resistance.
The tieback-deadman structure resists forces that would otherwise cause the wall to lean, as for example, when a seawall is pushed seaward by water trapped on the landward side after a heavy rain. Grouted tiebacks can be constructed as steel rods drilled through a concrete wall out into the soil or bedrock on the other side. Grout is then pumped under pressure into the tieback anchor holes so that the rods can utilize soil resistance to prevent tieback pullout and wall destabilization.
A tie-back anchor and the method for use thereof in connection with shoring systems wherein support for upstanding shoring components is provided by a plurality of tension cables or tendons placed outwardly of an excavation into undisturbed earth structures. A hollow tubular element having outwardly extending discontinuous helix formed flight elements is augered into place.
A plurality of load transfer pins or bolts extend inwardly within the tube structure to positions of potential interference with the tension cables and the longitudinally separated bushings locked on separate cables. After placement of the tube structure and loose cables, a high strength grout is introduced into the tube whereby subsequent tension loadings on the cables and bushings is transmitted by the grout to the interfering load transfer pins, the tube structure, the helix flights thereof and the supporting earth structure. Pretensioning components inclusive of tapered bushings and wedge locks are used to transfer the developed tension loadings to walers, soldier beams and the sheeting of the shoring system.