the pile achieves full penetration, the driving spline enters an annular 

 groove at the upper end of the pile; all rotation of the pile stops even 

 if the motor continues for a short time. The vertical position of each 

 pile is maintained by the driving spline in the annular groove, as well 

 as by a spring-loaded locking pawl, a simple but sure method of preven- 

 ting the platform from moving with respect to the piles under vertical 

 loading should the driving spline line up with the driving groove upon 

 stopping of the motor. The illustrated configuration of pawl is des- 

 criptive; in the actual case, a broad latch which would span the driving 

 groove would probably be used. Only two control functions, both of which 

 could be made automatic, are necessary. First, the hydraulic motor drive 

 would be actuated by a mechanical valve or limit switch when the contac- 

 ting pad reached soil. Second limit switches (3 in series) or comparable/ 

 mechanical hydraulic sensors would shut off the hydraulic motor when all 

 three piles were fully driven; these could readily be combined with the 

 locking mechanism. 



CONCLUSIONS AND RECOMMENDATIONS 



On the basis of the evaluation of design concepts for a seafloor 

 pile emplacement system it was concluded that a screw-pile emplacement 

 system would be the most effective in meeting the given operating 

 requirements. Most of the system components have already been developed, 

 and the difficulty involved in system integration is small. 



A preliminary design for a pilot-model screw-pile emplacement sys- 

 tem was developed and is presented. It is recommended that this pilot- 

 model be developed. The development can be conducted in several stages. 

 For instance, the control and feedback subsystem should be developed 

 first by "breadboarding" to study the most effective balance of automatic 

 and operator control. Following this study final decisions can be made 

 concerning use of multiplexing versus hard-wire controls and the use of 

 the corer E-M cable versus purchase of a new cable. The installation 

 and electrical subsystem could then be developed, followed by develop- 

 ment of the foundation/anchorage subsystems. Staged development would 

 permit the greatest flexibility for the final design and would also 

 permit relatively low annual budgets. 



ACKNOWLEDGEMENTS 



The efforts of Mr. E. J. Beck on the mechanical design aspects of 

 this program, and in particular on the concept for a simplified system 

 for anchorages, are gratefully acknowledged. 



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