ANCHORS AND TIEBACKS
Tie-backs may be used to avoid overstress due to large cantilever lengths. Stressed anchors (tiebacks) are constructed by drilling holes through the wall and into the adjacent ground at a downward inclination. The diameter, depth, inclination angle, location and the number of tiebacks are predetermined by design engineers and they achieve their capacity by being extended and bonded into the ground behind the expected failure plane. Steel strand cables (tieback cables) are inserted into the drilled hole which is then pressure grouted with concrete. Once the concrete has set, a strand gripper and gripper casing is placed over the cables and tensioned using a hydraulic jack. Continuous walers are used across rows of tiebacks and along with capping beams, they protect against progressive collapse of tieback wall systems by redistributing loads to adjacent ground anchors.