Several reported designs use similar values (Sakuta et al., 1975; Mutoh, 

 1975). 



Simple Deadweight . As shown by Table 18, a deadweight of 780 MN 

 (175 x 10 b lbs) is required to resist Gulf Stream loading. The extreme 

 size (83 m x 83 m x 8.3 m) of this anchor make handling, transportation 

 and installation major problems. 



Two possible techniques for accomplishing these tasks aresuggested. 



First, the anchor could be fabricated in a large dry dock, then barged 

 or towed to the site using external or internal buoyancy tanks. A buoyancy 

 or heavy lift system would also be required to lower the anchor to the 

 seafloor. Second, the anchor could be cast in place on the seafloor. 

 Again, a heavy lift sytem would be needed to pre-position the framework on 

 the ocean floor. Technology for pouring concrete in the ocean at a depth 

 of 460 m has not been demonstrated to date, but is probably within reach 

 in the near future. 



The advantages of the deadweight are its simplicity and reliability. 

 It does not require that complex underwater operations be carried out in 

 the high energy Gulf Stream environment; and it is not likely to fail 

 catastrophically. 



Note that for all deadweight calculations a height to width ratio of 

 0.1 was used. A ratio of as much as 0.4 is probably acceptable on a rock 

 seafloor. This would reduce the lateral dimension shown irv Table 18 to 

 about 0.7 of the stated values. 



Grouted Deadweight . A substantial reduction in anchor size results 

 if grout, injected beneath a deadweight, is used to resist lateral load. 

 Since grout is ineffective in tension, the deadweight described in Table 18 

 was designed with a mass sufficient to resist the vertical load. The shear 

 strength of the grout-rock bond is assumed to resist lateral load. A bond 

 shear strength of 69 kPa (10 psi) is required over the entire deadweight 

 bottom surface to resist the 180 MN lateral load. Careful seafloor surface 

 preparation (possibly by suction dredging) is required to insure sufficient 

 bond integrity. . 



Again, a heavy lift system would be needed to install the anchor. 

 By grouting or gluing the dead weight to the underlying rock, size is 

 reduced, but cost is increased, installation complexity is increased, and 

 a questionable bond with the seafloor exists. 



The grouted deadweight concept might be carried one step further 

 Use of an underwater curing epoxy, instead of a coment grout, could reduce 

 anchor size drastically. Epoxy grouts can sustain tension as well as shear. 

 However, there would be an even more critical dependence on the bond at the 

 seafloor Experience with underwater epoxies is limited. Their long term 

 performance in a marine environment under heavy loads has not been proven 

 conclusively. Further, bonding of the anchor to a cleaned rock surface may 

 not ncrease anchor holding capacity since the rock itself may separate 

 along bedding planes. Thus, bonding of an anchor block to a rock surface 

 would be an uncertain operation at best. 



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