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The AJ geometry creates maximum hydraulic stability by providing for both high interlock and high porosity. Six legs radiate out from the centre mass and interlock closely with adjacent units. The patented fillets assure optimum spacing and voids in the tightest interlocking configuration. In a uniform placement configuration, three legs are in contact with the subgrade and each unit interlocks with the six neighboring AJs. The figure below shows AJs in uniform placement.

Uniform placement AJs

Waist Ratio

Slender AJs are used in river applications and thick units are used in coastal applications. The thickness of the arm divided by the overall length of the AJ is the waist ratio. Standard River AJs have waist ratios of 1/6.5 or 1/6.0. Standard Coastal AJs have a waist ratio of 1/5.2. Very thick units with a waist ratio of 1/4.0 can be used as an underlayer or for patches on structres where other types of armour units have failed. AJ size is generally specified by the armour unit length for River AJs and by weight for Coastal AJs.

AJs are available in either square or round ends.