1.4.4 STAKE PILES. This type of anchoring system which consists of wood or steel
pilings driven into the bottom can be used in certain moorings as an anchor. The
disadvantages of this type system are that the stake pile is fixed and cannot absorb
shock energy as well as an anchor, and that a pile-driving rig is required for
1.4.5 PEARL HARBOR ANCHOR. This anchor is essentially a concrete sinker with a
wedge shape (see Figure B-23). It is relatively inexpensive to build and can be
fabricated onsite. The size and weight required to obtain adequate holding power,
however, make the anchor bulky and difficult to handle.
1.4.6 PROPELLANT-EMBEDMENT ANCHOR (PEA). This relatively new anchor has
been utilized in a number of recent mooring installations. An anchor fluke is
emplaced in a gun assembly. The entire assembly, consisting of the gun (launch
platform), downhaul cable, and anchor fluke (see Figure B-24), is lowered to the
bottom. The gun is then fired and the fluke, depending upon the material of the
ocean bottom, is driven 10 to 40 feet into the subsurface strata (see Figure B-25).
Attached to the fluke is a wire rope downhaul cable (2 to 3 inches in diameter). The
upper end of this downhaul cable is then connected to a wire rope pendant and the
anchor chain subassembly or is directly connected to the anchor chain subassembly
by swage and shackle fittings.
The gun assembly is recovered for re-use. A
photograph of a propellant-embedment anchor being prepared for installation is
shown in Figure B-26.
1.5 CATHODIC PROTECTION SYSTEMS. Cathodic protection is an electrical method
of preventing corrosion of metallic structures in a conducting medium (usually
water or soil) by placing an electrical charge upon them. The charge is supplied by
direct current from an anode that consumes itself (sacrificially) in generating the
c u r r e n t or by rectified alternating current.
Cathodic protection systems are
discussed in Section 8 of this manual.