However, cuttina edqes are desirable, at least around the periphery 

 of the deadweiqht, to prevent undercuttinq of the anchor block by scour. 

 Further, the substantial submerqed weiqht must be made available anyway 

 so that weiqht should also be used to drive some minimal cuttinq edqe 

 desiqn. The base shear design assumes a souare olan anchor block of side 

 lenqth B and heiqht H equal 0.1 x B with the block material havinn an 

 averaae submerged unit weiqht, y, of 13.5 kN/m 3 (86 pcf). 



Fioure 49 indicates that a deadweiqht block with a side lenqth, R, 

 of 56 m (184 ft), a Z/B ratio of 0.05, and other Darameters as above would 

 resist the 180 MN lateral loadinq of the Gulf Stream. The force required 

 to embed the cuttina edges is 64 MN (14.5xl0 6 lbs), for all nractical our- 

 ooses the same as the 62MN load capability of the Glomar Explorer . In 

 practice the 64 MN, 56 m sauare deadweiaht with 2.8 m lonq cutting edqes 

 would consist of a structural prestressed concrete compartmentalized box 

 Dlaced on the bottom by a heavy lift system. The cuttinq edqes of this 

 box would be embedded uniformly by the submerged weiqht of the empty box. 

 Given the box weiqht of 64 MN and the prestressed concrete unit weiaht 

 in seawater of 13.5 kN/m 3 (86 pcf), the volume occupied by the prestressed 

 concrete would be 4,800 m3 (169,000 ft 3 ). The 56 m x 56 m x 5.6 m high 

 box would enclose a volume of 15,300 m 3 (623,000 ft 3 ) of which 70 percent 

 would be void space at the time of embedment. This void soace would then 

 be filled with a material selected to provide the necessary .submerged 

 weiaht (1) to maintain the deep, olanar zone of slidina, (2) to resist 

 the overturning moment, and (3) to resist some small uplift load from a 

 non-zero mooring line angle. If the box were entirely filled with concrete, 

 its submerged weight would be 240 MN (54x10^ lbs), sufficient to resist 

 overturning and some small amount of uplift component. 



Summary . The lateral load and skirt embedment analyses together 

 then have resolved the general shaoinq and sizinq of the deadweiaht anchor 

 system for OTEC. Anchors on cohesive sediments will require cuttinq edae 

 lenqth, Z, of 0.1B; those on non-cohesive sediments reauire shorter cuttinq 

 edaes to facilitate embedment with Z = 0.05B appropriate. Emplacement of 

 anchor sizes sufficient to resist the deep ocean lateral loadinq of 18 MN 

 (with near zero moorina line anqle) is feasible with available technology 

 and eauioment. Emplacement of anchors sufficient to resist the Gulf Stream 

 lateral loadina of 180 MN (with near zero mooring line angle) on a cateaory 

 D soil (sand-like) is also possible today. Only the anchor conceptual 

 desian for resisting the Gulf Stream loadinq on a category C soil (clav- 

 1 ike) remains a significant problem because of the difficulty of properly 

 anplyinq driving force to uniformly embed the cutting edges. Viable 

 concepts for resistina heavy loads on clay have been suqaested but remain 

 to be evaluated and compared. 



Bearina Capacity Analysis 



Introduction . The remaining section of this chanter briefly presents 

 bearing capacity data. In aeneral, the results of this section suqgest 



98 



