302 Bulletin, Scripps Institution of Oceanography 
(a) the holding qualities of various types of bottom deposits, and (b) the holding 
power of various types of anchors and anchoring systems. It would be very useful 
to have a yardstick with which the anchor-holding qualities of bottom deposits 
could be measured, or to have some easily measured characteristic to which they 
could be related. 
At least one attempted approach to this problem has been published (Conti- 
nental Copper and Steel Industries, 1956), and no doubt there are others. Because 
this report indicates the kind of useful information that can be obtained, the 
following extracts from it are included here (bearing in mind that it describes 
conditions in a particular area): 
The ocean bottom conditions in this area are likely to be stratified layers of inorganic clays, 
globigerina ooze and sands. The sedimentary layers grade both laterally and vertically into 
different kinds of sediments. Inorganic clay is the predominant sediment. 
Bearing strength of this deep-sea material can be inferred: it probably behaves like sub-aerial 
sediments of the same type and characteristics. A few direct observations are pertinent. Glacial, 
ice-rafted boulders weighing seventy-five pounds have been dredged from the surface of the 
deep sea clays. We infer from this that rocks of density 2.50 have not sunk deeply into the bottom 
mud since the glacial age. A few scattered soil tests have been made on disturbed samples taken 
by coring devices. One sample was subjected to consolidation tests and the natural water content, 
and the liquid plastic limit has been established. 
From these tests the cohesion can be estimated to be, between zero and five feet below ocean 
bottom, two hundred pounds per square foot. From then on, the cohesion increases to approxi- 
mately three hundred pounds per square foot at a depth of eleven feet and this increase continues. 
Concerning the holding power of anchors, Riesenberg (1936) describes pulling 
tests on two types of stockless anchors in three types of bottom (soft mud, hard 
sand and gravel, and hard clay). Anchor A weighed 3,145 pounds, and anchor B 
weighed 2,375 pounds. The results of the tests (as read on a 100-ton gauge) are 
shown in table 3. The scope of chain in the above tests varied between approxi- 
mately 5 and 9, and the pull-out tensions varied from zero to approximately five 
times the weight of the anchors. By comparison, as shown in table 4, the holding 
power of at least one common type of anchor is claimed (by a supplier) to be “up 
to sixty times the weight of the anchor.” 
Common types of anchors in general use are designed to be most effective when 
the pull is parallel or nearly parallel to the bottom. The weight of the attached 
TABLE 3 
Houpine Power or Borrom 
. h Chai Strai 
Deposit Ga bation) (in fathoms) Anchor Guay 
Softmnudy eee cece eee 7 38 A none 
Softimudeeyn ao escce een: a 35 B oato 
Hard sand and gravel........... 6 53 A 2.0 
Hard sand and gravel........... 6 53 B 6.0 
Hat diclayionr sce stance taco 6 53 A 6.5 
Hardiclay ance cee scene 6 53 B 6.0 
