Q. Factors determining the stability of a single armour unit

There are mostly three major factors that govern the stability of an armour unit, viz gravity, intertangling and squeezing. Evidently it is beyond doubt that ability of the armour unit to stay in place must be closely related to gravity force. Alternatively the geometry of armour unit also affects its stability. For example with the difference in ability to intertangle, their resistance to pulling out by waves varies. Moreover squeezing forces by gravity also affects the stability of armour unit that is dependent on frictional forces in all directions.