Pioneering Percussion Driven Earth Anchors (PDEA®) for 40 Years


The Mechanical Ground Anchor System

How A Mechanical Anchor Works

There are three steps to the installation of a ground anchor system:




The same three basic steps apply to the installation of all ground anchor systems, from the smallest S2 to the largest B10.

Typical Anchor Behaviour


Loadlock – The first stage is where a load is applied to rotate the ground anchor into its loadlocked position. Elements of both load and extension are present.

Compaction & Load – The second stage is where the anchor system is generating a frustum of soil immediately in front of the ground anchor. At this point load normally increases with minimum extension. The soil type will affect the overall extension.

 Maximum Load Range – The third stage is where the ground anchor produces its ultimate load. As the anchor load approaches the bearing capacity of the soil, the rate of increase in load will reduce until bearing capacity failure of the soil takes place.

Bearing Capacity Failure – Caution: If the mechanical shear strength of the soil is exceeded, the residual load will decrease with continued extension as the ground anchor shears through the soil.

Stress Distribution and Bearing Capacity

The stress distribution in front of a loaded anchor can be modelled using foundation theory. The ultimate performance of a ground anchor within the soil is defined by the load at which the stress concentration immediately in front of the anchor exceeds the bearing capacity of the soil.

Factors that will affect the ultimate performance of the anchor include:-

  • Physical properties of the soil
  • Size of the ground anchor
  • Depth of installation
  • The load applied

Platipus ground anchors perform exceptionally well in a granular soil, displaying short loadlock and extension characteristics, a broad frustum of soil immediately in front of the anchor and extremely high loads.

Stiff cohesive soils, such as boulder clays, can also give outstanding results. However, weaker cohesive soils, like soft alluvial clays, can result in long loadlock and extension distances and a small frustum of soil in front of the ground anchor. Consequently these conditions require a larger size of ground anchor and if possible a deeper driven depth to achieve design loads.

Granular Soils (Drained)

Cohesive Soils (Undrained)