completely automatic mechanical devices and will not require control 

 telemetry. The auxiliary footing is necessary to stabilize the unit when 

 one of the piles is being rotated, Figure 4c. When the pile is fully 

 embedded, an automatic mechanical connection is made between the pile and 

 the template, and subsequent piles are emplaced. When all piles are in 

 and the load-bearing connections are established, the emplacement system 

 is detached from the template and retrieved, Figures 4d and 5. If a 

 given installation must be more nearly horizontal than is possible with 

 the planned pile free-fall method, a leveling system can be included; 

 the leveling would be done before the piles were emplaced. Figure 6 

 shows the system block diagram for the pilot-model system. 



In the following sections the five subsystems are described and the 

 major components of each subsystem are defined. 



Foundation/Anchorage Subsystem 



The foundation/anchorage subsystem consists of the template, the 

 piles, the main load-transfer connections, the one-way travel grips 

 and auxiliary footing, the pile release mechanism, and guide bearings 

 that keep the piles aligned in the template, Figure 7. For the preli- 

 minary structural design of the template each side of the template was 

 assumed to be a beam with ends partially restrained against rotation, 

 supporting a centerpoint load of 75 kips. For a span of 10 feet, the 

 required beam is approximately 18 inches deep and weighs 50 pounds per 

 foot. The template will be of all-welded, steel construction and the 

 sides can be fabricated as trusses, as shown in Figure 7, or from 

 standard rolled sections. 



The pile cross section must resist compression, tension, bending, 

 and torsion loadings. However, the maximum values of these loadings 

 are not expected to occur simultaneously, and the effects of combined 

 loadings will be negligible. The loading that controls the cross- 

 section dimensions is the maximum bending (lateral) loading of 25 kips 

 per pile. For the preliminary design a 10-inch, square-tube cross 

 with a wall thickness of 3/8 inch was chosen. A lateral load analysis 

 indicates that this cross section is adequate. Failure will be induced 

 in the soil rather than the piles. 



The vertical capacity and emplacement torque of screw piles of 

 several different configurations were estimated for various likely 

 seafloor soil conditions. As noted above, these calculations indicate 

 that the helical blades should range in size from about 16 inches to 

 30 inches in diameter. The calculations also indicate that more than 

 one blade per pile will be required for adequate capacity and proper 

 installations in all likely seafloor soils. The calculations show that 

 pile penetrations will range from a minimum of about 15 feet in dense 

 cohesionless soils to about 50 feet in soft cohesive soils. 



15 



