Tiebacks are used to provide the lateral resisting force for many of the retaining walls that Schnabel builds. They are constructed by grouting a high strength steel bar or strand bundle into the soil behind the retaining wall face. 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. Tiebacks 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.
A slight variation of the tieback is the tiedown. The construction is similar, but the direction of the force is primarily vertical rather than horizontal. Tiedowns are used to resist hydrostatic uplift on structures built below the water table and seismic loads created by earthquakes.
In addition to their use in the construction of new retaining structures, tiebacks are also used to stabilize existing retaining walls which are moving or deteriorating. Schnabel has patented systems for the tieback connections and facings used for the repair of distressed MSE and cantilevered retaining walls. Tiebacks are also used to stabilize landslides.