Deadman anchors are made of reinforced concrete. They consist of two elongated beams that run the full length of the tank. The beams, usually 12 inches or so wide and high, rest on the bottom of the excavation just outside the diameter of the tank itself. Straps running across the top of the tank connect the two anchors to each other.
The weight of the beams goes a long way toward holding down the tank if it seeks to float. More important, a portion of the backfill in the excavation also bears directly down on each of the two deadman anchors placed along the sides of the tank. The weight of this backfill provides additional downward force to prevent flotation.
The term “deadman anchor” has long been used in the construction trades to describe a block of concrete, or similar object, buried in the ground for the purpose of holding down a connected structure.
See also Tank anchors.