Tieback (geotechnical)
Encyclopedia
A tieback is a horizontal wire or rod, or a helical anchor used to reinforce retaining wall
s 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.).
Retaining wall
Retaining walls are built in order to hold back earth which would otherwise move downwards. Their purpose is to stabilize slopes and provide useful areas at different elevations, e.g...
s 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
Seawall
A seawall is a form of coastal defence constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides and waves...
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
Grout
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints . Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel...
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.).