ULTIMATE LOAD = Also referred to as the pull out capacity. The minimum theoretical load which causes loss of equilibrium in part or whole of the soil surrounding the anchor. An adequate factor of safety should also be applied to satisfy the particular application and also to account for any uncertainty within soil parameters.

CRITICAL DEPTH = Since vertical effective overburden stress is a function of soil unit weight and vertical depth, it would then follow that anchor capacity should increase linearly with increased overburden depth (within granular soils). In a uniform soil, we know this not to be the case below a certain depth (known as the Critical Depth and is a function of the anchor size). The Critical Depth is defined as the limiting depth where there is no (or very little) resulting further increase in the ultimate bearing capacity with increased vertical effective stresses. However, if the soil becomes more or less dense below the critical depth and the internal friction angle varies, an increase or decrease in ultimate bearing capacity may ensue, but is not as a result of increased overburden stress. The maximum anchor performance may also be limited by the ultimate material strength of its resulting component parts. The anchor load indicator has been modeled to consider these limiting attributions.

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