depths in soil category A are found as follows: 



(1) Computed required soil strength using anchor dimensions 

 (Table 2) and peak design capacity. 



(2) Obtain depth for required soil strength from shear 

 strength versus depth curves (Valent et al., 1976). 



(3) Plot depth versus anchor weight (see Figure 5). 



The required penetration of a 45 Mg (100,000 lb) anchor would be 

 33.5 (110 ft) and total setting distance would be about 201 m (660 ft). 

 Also plotted in Figure 5 is the actual penetration data for the STAT0 

 anchors in San Francisco Bay mud; the strength of this mud is wery 

 similar to category A soil. The remarkable agreement between actual and 

 predicted penetration supports the extrapolated curve. 



Pick Type Anchor . The BRUCE and HOOK anchors are pick type anchors. 

 Relatively recent developments, they appear equally efficient (about 20/1 

 in category A soil and 28/1 in category D soil). 



More data are available for the BRUCE anchor and it will, therefore, 

 be used for extrapolation. The BRUCE anchor has one inherent advantage 

 over the HOOK anchor in that it will always embed when pulled laterally, 

 even if it lands on the shank side during deployment. This greatly simp- 

 lifies deep water deployment. 



Characteristics of the BRUCE anchor taken from company literature 

 (Bruce, Ltd., 1974) are presented in^Table 3 along with those of several 

 extrapolated anchors to 455 Mg (1x10 lb) size. /The 455 Mg anchor, if 

 it could be fabricated, would yield 89 MN (20x10 lbs) holding capacity. 

 The limiting characteristic, as with the STAT0 type, will be steel stress. 

 Maximum holding capacity is plotted versus anchor weight for category A and 

 D soils and for various limiting steel stresses in Figure 6. The steel 

 currently used for the BRUCE anchor has a yield stress of 500 MPa (72.5 ksi' 

 which is greater than that required for the existing 6.4 Mg (14,000 lb) 

 anchor. Maximum stress at maximum holding capacity for the 6.4 Mg anchor 

 in the shank is 21 MPa (30 ksi) in soft clay (category A) and 29 MPa (42 ksi 

 in sand (category D). From Figure 6, assuming a construction capability 

 exists, it is apparent that approximately a 17.8 MN (4xl0 6 lb) capacity 

 91 Mg (200,000 lb) anchor could be fabricated using exactly the same steel 

 that is used in the 6.4 Mg (14,000 lb) anchor by simply seal ing-up-j t^e 

 dimensions in proportion to weight to the one-third power, i.e., W 



Also included in Figure 6 is a curve representing the theoretical 

 relationship between holding capacity and anchor weight in that regime ^ 

 where steel stress control efficiency, i.e., holding capacity -height) 

 The initial point of the curve came from the company advertised limiting 

 load of 2.98 MN (670,000 lbs) for the 6.4 Mg anchor fabricated from 

 500 MPa steel . 



Mud Type Anchor . Only two of this type anchor are known to exist 

 and are called the PARAVANE anchor and the DORIS Mud anchor. The existing 

 sizes and company advertised capacities of the PARAVANE or "Kite" anchor 

 are provided in Table 4. These capacities appear to be based upon a soil 



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