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Construction

Ground anchor

ActivePublished
Key innovation
Transfers a structure's tensile/uplift loads into the surrounding soil instead of relying solely on the dead weight of the foundation.
Category
Construction
Abstraction level
Building block
Operation level
Deployment
Use cases
Retaining walls (tieback anchors)Guyed masts and telecommunication towersDeep foundationsGround-mounted solar array foundationsTemporary structures (e.g. tents)Residential foundations (decks, sheds, stairs)Rail and road infrastructure

How it works

The anchor is installed by impact driving (with a drive rod and hammer), rotation (helical flights torqued into the soil), or drilling with cement-grout injection. After load-locking (e.g. rotating it 90 degrees) the tensile load is transferred to the ground: resistance is generated by a frustum-shaped cone of soil above the anchor and by the bearing and friction of the flights. For screw anchors, the installation torque correlates with capacity and is used to verify the design.

Problem solved

Structures subject to uplift, overturning or lateral forces — guyed masts, retaining walls, towers, and light or temporary foundations — cannot rely on their own weight alone. A ground anchor transfers these loads into the surrounding soil, providing tensile stability without the need for massive gravity foundations.

Components

Anchor shaftLoad transfer

Steel shaft (often a tubular hollow section) that transfers the structure's load into the ground.

Helical flightsBearing/uplift capacity

Helical plates welded to the shaft that generate bearing and uplift capacity as the anchor is screwed into the soil.

Anchor head / load-lockAnchoring/connection

Element that locks the anchor after installation and connects it to the structure or tendon.

Grout bond body (for tiebacks)Bonding tendon to soil

Cement-grout body bonding the tendon to the soil in grouted tieback anchors.

Evolution

1848
Screw piles described by Alexander Mitchell
Inflection point

Irish engineer Alexander Mitchell described screw piles in the Civil Engineer and Architect's Journal; already in use about a decade earlier (e.g. screw-pile lighthouses).

1912
First practical earth anchor (Albert Bishop Chance)
Inflection point

Albert Bishop Chance invented the first practical earth anchor in Centralia, Missouri, after an ice storm knocked down telephone poles.

Hyperparameters (configurable axes)

Embedment depthCritical

Depth to which the anchor is installed; selected based on soil analysis.

Helix diameter and countHigh

Number, diameter, thickness and spacing of helical flights along the shaft.

Installation torqueHigh

Torque during installation, correlating with capacity and used to verify the design.

5 000 – 500 000 N·mTorque range of hydraulic powerheads used to install screw piles (source: Wikipedia, Screw piles).
Shaft diameterMedium

Shaft diameter governing stiffness and maximum anchor capacity.

do ~300 kN (osiowo), ~200 kN (wyrywanie), ~25 kN (poprzecznie) — małe średnice; >2500 kN — duże średniceTypical screw-pile capacities per Wikipedia (Screw piles).