should be applied in all cases where a clay bottom is encountered. The 

 c = 1 psi curve is applicable to the behavior anticipated of deep ocean 

 clays. No research applicable to silt bottoms is available. Therefore, 

 to be conservative, the same safety factor used with clays should also 

 be used with silts. 



Cohesionless Soils 



As discussed earlier, the shear strength of cohesionless soils is 

 purely frictional with the cohesion, c, being equal to zero. Equation 2 

 then reduces to 



F^ = AY, D N (0.84 + .16 B/L) (6) 



1 b q 



The problem i^n estimating the short-term holding capacity in sands 

 is in estimating N . The suggested _technique for doing this is presented 

 in Figure 4 in the form of plots of N as a function of relative embed- 

 ment depth, D/B, and soil friction angle, (j) . The curved portions of 

 the plots were derived from the theor^etical work of Vesic (1969) . The 

 points at which the plots break and N becomes independent of D/B are 

 the points of separation between "shallow" and "deep" anchor behavior. 

 In "shallow" behavior the zone of soil failure which occurs when the 

 holding capacity is reached extends to the surface, while in "deep" 

 behavior it does not. The points of separation between the two forms of 

 behavior were ob_tained from the work of Meyerhof and Adams (1968) . The 

 independence of N with respect to D/B after "deep" behavior has begun 

 is in complicance\rith generally accepted concepts. 



The recommended procedure for predicting the short-term holding 

 _capacity in cohesionless soil (sand) is to use Equation 6 with values of 

 N obtained from Figure 4. Techniques for estimating the soil parameters 

 ^and Y , will be given in a later section. 



The problem of suction probably does not occur with cohesionless 

 soil because of high permeability which allows negative gage pressures 

 beneath the anchor to dissipate rapidly. The results of short-term field 

 tests may be assumed to represent the proper short-term holding capacity. 



LONG-TERM STATIC HOLDING CAPACITY 



Cohesive Soil 



The long-term static response of cohesive soils may be separated into 

 the areas of drainage and creep. 



Drainage . Drainage occurs whenever soil pore water pressures, either 

 negative or positive gage, are set up during loading. Almost any form 

 of loading will generate pore pressures, so water flow into or out of 

 the soil with time is to be expected in virtually all cases. The water 

 flow in turn will cause a change in soil density with a resulting change 



