SELECTION OF PILE EMPLACEMENT SYSTEM CONCEPT 



Operating Requirements 



The operating requirements for a seafloor pile foundation were 

 designed to apply to a generalized installation rather than a specific 

 seafloor structure. This was done to ensure that the choice between 

 alternatives would not be influenced by the special characteristics 

 or design requirements of a given installation. In the initial phase 

 of the selection process, the operating requirements were given as 



follows 



2. 



The system must be operable in water depths to 6,000 feet. 



2. The system must be able to emplace several piles in a multi- 

 sided structure in correct relative positions. 



3. Each pile must be within 2 degrees of plumb. 



4. Pile emplacement must be possible in sea states up to and 

 including sea state 3. 



5. Each pile should have an ultimate uplift or bearing capacity 

 of 200 kips. 



Based upon these criteria, concepts for several emplacement methods were 

 developed and compared. The primary emphasis in the initial phase was 

 upon the effectiveness of the emplacement device (i.e., vibratory driver, 

 impact hammer, etc.) rather than upon the performance of an overall 

 system. Details of the initial-phase comparison are given elsewhere. 2 

 It was determined that vibratory driver, screw pile, and jack-in systems 

 were feasible for development. 



The emphasis in the second phase was upon the performance of a 

 complete pile emplacement system utilizing each of the three emplacement 

 methods. In this comparison the operating requirements were modified to 

 reflect the characteristics of the complete system. The operating re- 

 quirements relating to water depth, verticality of the piles, and sea 

 state were retained without change. For each system only the minimum 

 required number of piles was considered. The minimum number for 

 vibratory-driver and screw-pile systems is three piles; for the jack-in 

 system, five piles are required. The minimum capacity requirement was 

 reduced to an ultimate load capacity for the system of 150 kips in uplift 

 or bearing, and a 75-kip ultimate lateral load requirement for the system 

 was added. 



In addition to the above requirements, the following design goals 

 were established: 



