3 October 2005
DRAG-EMBEDMENT ANCHOR SPECIFICATION. Drag-embedment
anchors are carried on ships and used in many fleet-mooring facilities. Key
considerations in selecting an anchor are: soil type, anchoring holding capacity, anchor
weight, anchor stowage, cost, availability, and installation assets. Note that in SI units
the anchor mass is used to characterize anchor size, while in U.S. customary units the
anchor weight as a force is used.
Drag-embedment anchor holding capacities have been measured in full-
scale tests, modeled in the laboratory, and derived from soil analyses. Empirical anchor
holding curves were developed from this information (Naval Civil Engineering
Laboratory (NCEL), TDS 83-08R, Drag Embedment Anchors for Navy Moorings).
Predicted static ultimate anchor holding is given by:
HM = HR(WA / WR) b
ultimate anchor system static holding
capacity (kips or kN)
reference static holding capacity
weight of the anchor in air
(for SI units use anchor weight in kilograms;
for U.S. units use anchor weight in pounds
reference anchor weight in air
(for SI units use 4536 kg;
for U.S. units use 10000 lbf)
Values of HR and b depend on the anchor and soil types. Values of these
parameters are given in U.S. customary units in Table 5-3 and for SI units in Table 5-4.
Figures 5-4 and 5-5 give holding capacities of selected anchors for mud
and sand seafloors.