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.
Helical anchors are screwed into place. Their capacity is proportional to the torque required during installation. This relationship is in accordance with the equation Qt = kT where Qt is the total tensile resistance, k is an empirical constant and T is the installation torque. These anchors are installed either for small loads in short sections (as pioneered by the AB Chance company) or for larger loads and in long continuous lengths (as pioneered by Helical Solutions Inc.).
Topics in geotechnical engineering Soils Soil properties Soil mechanics Geotechnical investigation Laboratory tests Field tests Foundations Retaining walls Slope stability Earthquakes Geosynthetics Instrumentation for Stability Monitoring
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