from about 28.6 horsepower per pile to about 3 horsepower per pile. By 

 driving all three piles at once the total horsepower requirement is 9 

 horsepower. For approximately one-half hour of driving time the power 

 could be supplied by a submerged battery pack. Approximately 12 

 kilowatt-hours of electric energy would be required, and ultimate up- 

 lift capacities of approximately 120 kips in cohesive soils and 90 kips 

 in cohesionless soils would result. 



This system would utilize a much-simplified control system since 

 a single valve would control all three motors. All controls would be 

 automatic and would be contained on board the installation system. 

 Thus, the need for an electro-mechanical cable is eliminated. The 

 operation would be as described below. 



Arrival at the bottom would be sensed by a pad as previously dis- 

 cussed. The pad could be made to release all three kellys so that the 

 augers would penetrate the loose surface layers by gravity. The verti- 

 cal aspect of the platform (level) could be controlled by a buoy, rigidly 

 attached but well above the platform. In principle, the entire assembly 

 could be lowered in free-fall with the buoy limiting the rate-of-descent . 



The "contact pad" could with very simple mechanical valving or 

 electric relays activate an automatic sequence to simultaneously drive 

 all three piles to full depth. Upon full penetration, a simple spring- 

 loaded pawl at the lower end of the kelly drive would fix the platform 

 with respect to the piles. 



The power components, if inexpensive enough, could be left on the 

 platform. If it were desired to retrieve the power components, a plat- 

 form could be released by a time mechanism or command from the surface. 

 The buoyancy element would probably require releasing and removal to 

 provide a clear foundation for subsequent mounting of equipment or a 

 structure. 



While free-fall appears to be practical using a buoy as described, 

 a minimum cable to establish the foundation's location would be desir- 

 able. This would also be useful in guiding the buoy and power components 

 to the surface, as well as in guiding a structure to the installed 

 foundation. 



Furthermore, a simpler drive system can be utilized with the smaller 

 cross-section piles. This system is shown in Figure 14. The square 

 kelly is replaced with a round pile in which are machined two grooves 

 circumferentially at the top and bottom. At the middle of the figure 

 (Figure 13) is shown the lower end of the pile, with the driving spline 

 not aligned with the driving groove; the pile is thus held from dropping. 

 As the pile is rotated by the hydraulic motor the driving spline enters 

 the driving groove and no longer prevents the pile from falling. When 



20 



