Piles With Enlarged Tips (PET) 



This system is similar to the belled piles used in the industry to 

 achieve an increased end-bearing resistance or uplift capacity. However, 

 belled piles for nearshore and offshore applications are very costly and 

 time consuming. The PET developed for this study basically follows the 

 proven techniques used on land. Two alternates were developed and are 

 described. 



Alternate A - Piles Installed With a Withdrawable Tube . Figure 31 

 is a conceptual drawing of this system. This system is very similar to 

 the Franki piles, the Alpha piles or the pedestal piles (Tomlinson, 1977). 

 To use this system: 



• Lower the tube to the sediment surface. 



• Drive the tube down to the correct depth by using an internal 

 drop hammer. 



• Hold the tube stationary and pour in gravel or concrete cement 

 to form a plug at the bottom of the tube. 



• Use the hammer on the plug to form a bulb (expanded) end. 



• Use the hammer to drive the pile into the bulb end. 



• Use the hammer to compress the concrete, grout, or granular back- 

 fill while removing the tube. 



The pile is installed when the tube and hammer are removed. This system 

 can be easily installed in most calcareous sands except in highly solid- 

 ified calcareous rock (such as limestone) . Since similar systems have 

 been successfully used elsewhere, it is anticipated that this system can 

 be readily used for calcareous application with a minimal amount of 

 development work. The development work should concentrate on under- 

 standing the pile-sediment mechanisms and the verification of load 

 carrying capacity increase. 



Alternate B - Modified Belled-Piles (MBP) . This system differs 

 from the conventional belled piles (Figure 32) . A regular open-ended 

 steel pile can be used with this system. To install a pile: 



• Use an impact or vibratory hammer to drive the pile to the cor- 

 rect depth. 



• Insert an internal expandable drill bit and underream a belled 

 end. 



• Remove the drill bit. 



• Pour concrete or grout, through the pile, into the belled end. 



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