Vat for some red clays has been found to be approximately 89 pounds per 
cubic foot. 
p = z(89 - 64) = 25z\Ibper ft? (11) 
Extensive experiments have indicated that the cohesion, c, in soft 
submerged clay may be as low as 0.25 p. This gives us a means of determining 
the shear strength, or cohesion, of this soil at any depth below the soil surface. 
Therefore, c = s = 6.25z 
The following table shows the shear strength (or cohesion) for a specimen 
of red clay from the surface of the ocean bottom to a depth of 10 feet below 
the soil—water interface. Strengths are shown in both pounds per square 
foot and pounds per square inch for ease of comparison with other data. 
Shear Strength, s 
Depth, z 
(feet) (psf) (psi) 
O O 0 
1 6.25 0.043 
D aS 0.086 
3 18.75 0.129 
4 25.0 0.172 
5 SilP25 0.217 
6 SES 0.260 
7 43.75 0.304 
8 50.0 0.347 
9 56.25 0.39 
10 62.5 0.435 
The shear strengths shown in this table are small but probably 
represent the worst case. Other ocean-bottom soils display shear strengths 
ranging upward from these figures to as much as 25 times greater. 
36 
