SAMPLE PROBLEM 



An example of an application of the suggested prediction procedure 

 follows. The step identifications are identical to those of the preceding 

 section. 



Problem 



A direct embedment anchor with a 3-foot-wide square fluke has been 

 placed to an embedment depth of 15 feet in a cohesive soil deposit. A 

 good quality core has been obtained and the measured vane shear strength 

 profile may be approximated by the curve of Figure 11. The buoyant unit 

 weight has been measured and found to be about 35 pcf throughout the 

 profile. 



The anchor is to provide support for one leg of a suspended sub- 

 surface array which is to be in service for several years. Determine the 

 design holding capacity of the anchor. 



Solution 



1. D = 15 feet 

 B = 3 feet 

 L = 3 feet 



A = 3 X 3 = 9 square feet 



2. The general soil type is cohesive. 



3. A core is available. 



(a) The vane strength distribution is as shown in Figure 11. 

 To determine the characteristic strength it is necessary to use Figure 

 7. D/B is calculated to be 15/3 = 5. The strength at the anchor, c , 

 is found from Figure 11 to be 3 psi. From Figure 7 (using linear inter- 

 polation between the c = 2 and c =3.5 lines), the quantity D /B is 

 found to be 1.75. Multiplying by B, D is determined as 5.25 feet. 

 This is the distance above the anchor at which the characteristic 

 strength, c, is to be found. Referring to Figure 11 again (and a depth 

 of 15-5.25 =9.75 feet), c is found to be 2.0 psi. 



The buoyant weight, Y, , is 35 pcf. 



(b) Using Equation 5: 



N = 3.8 (D/B) (^^ + 0.3) 

 c c 



N^ = 3.8 (5) (~pr + 0.3) 



^2.0 



N =12.38 

 c 



or 9 whichever is smaller, 

 Since^ 9 is smaller 

 N = 9.0 



16 



