An anchor weighing 64 Mg (140,000 lbs), providing a predicted lateral 

 holding capacity of 18 MN (4x106 lbs), is feasible. However, drag 

 embedment anchors have two strong disadvantages which render them unde- 

 sirable for use in the OTEC mooring: 



1. Drag embedment anchors must be loaded in only one direction, 

 whereas loading in the deep ocean environment will not be so limited. 

 The direction of load application can be limited by using a multi-point 

 moor with a drag embedment anchor at each leg. This approach would, 

 however, multiply the material cost of the moor by at least four. 



2. Drag embedment anchors must be embedded with a zero mooring 

 line angle and, for efficient operation, that line angle must remain near 

 zero. In order to attain a near-zero mooring line angle, a very long 

 scope of line must be used or "sinkers" in the form of concrete blocks of 

 heavy chain must be attached to or integrated into the mooring line to 

 absorb the vertical component of mooring line tension. Thus, the drag 

 anchor is best used in combination with a deadweight: the deadweight 

 resists the vertical component of load and the drag embedment anchor 

 resits the lateral component of load. Installation of a single leg for a 

 multi-point moor would require precise handling of a heavy deadweight and 

 a large drag anchor simultaneously. This would be an intricate operation 

 in deep water. Other anchor types offer greater versatility and savings 

 in materials. Drag embedment anchors are not desirable for mooring OTEC 

 in the benign deep ocean environment. Drag embedment anchors are even 

 less suitable for use inmaintaining the OTEC plant on station in the Gulf 

 Stream environment. To resist possible 180 MN (40x10^ lbs) loads, eight to 

 ten 64 Mg (140,000 lbs) drag embedment anchors, bridled together so as to 

 equally distribute the load, would be required. Proper installation of 

 this drag anchor group, and development and maintenance of the equally 

 distributed loadings; would be very difficult, rendering the concept not 

 suitable for use in the Gulf Stream environment. 



CLOSURE 



As a result of this effort, certain constraints on the OTEC mooring 

 design, and indeed possibly on the OTEC plant design, are evident. These 

 constraints have been alluded to here. Coherent presentation of these 

 constraints is made in the final report on the Phase I OTEC Anchor System 

 effort. 

 ACKNOWLEDGEMENTS 



The authors gratefully acknowledge Mr. Robert Rail for the structural 

 design input; Mr. Joseph Wadsworth for his assistance on the anchoring on 

 rock section; Mr. Lenny Woloszynski for his work on the pile capacity 

 analysis; and Mr. Fred Lehnhardt for his excellent efforts in preparing 

 the figures and tables for this document. 



124 



