Tiebacks are used to provide the lateral resisting force for many of the excavation support systems and anchored retaining walls that Schnabel builds. They are constructed by grouting a high strength steel bar or strand bundle into the soil or rock behind the failure surface of the retaining wall. After the grout has cured, every tieback is tested, and the load is locked in to limit movement.
In addition to their use in the construction of new retaining structures, tiebacks are also used to stabilize existing anchored retaining walls that are moving or deteriorating. Schnabel has patented systems for the tieback connections and facings used for the repair of distressed MSE, Bin and cantilevered retaining walls and has specialized equipment for drilling tiebacks through failing bulkheads along the waterfront. Tiebacks are also used to stabilize landslides where the tieback can be anchored in the soil or rock below the slide failure plane.
Tiebacks can be used for both temporary and permanent applications. Permanent tiebacks differ from temporary tiebacks in that the critical components of the tieback tendon and anchor head are protected from corrosion. Tie back construction can be anchored into most types of soil and rock. The capacity of the anchors in soil will vary depending upon soil type and installation method. Denser, granular soils will typically produce higher capacity tiebacks. Schnabel has installed tiebacks with lengths in excess of 200 feet and tested capacities of over 500 kips.