Strength Properties 



• Calcareous soils have a higher internal friction between grain- 

 to-grain contact than terrigenous soils (Home and Deere, 1962). 



• Friction angles of calcareous soils decrease with increasing 

 confining pressure. This reduction appears to be the result of 

 grain crushing (Datta et al. , 1980). Increasing grain crushing 

 induces decreasing shearing resistance until a limiting value of 

 shear resistance is reached. 



• Shearing can cause grain crushing and volumetric contraction. 



The summary of engineering behavior of calcareous soils represents 

 the state-of -knowledge at the beginning of this project. It is apparent 

 that the knowledge is meager and not well related to piles. 



STATE-OF-THE-ART PILE INSTALLATION PRACTICE 



Piles used nearshore and offshore are usually open-ended, steel 

 pipe piles. These piles are popular because they can be easily applied 

 to achieve long length, offer a good strength-to-weight ratio, minimize 

 soil disturbance during installation, and minimize driving resistance. 

 Also, it is more economical to install fewer long piles than more short 

 piles. 



Several techniques are currently used for installing piles in cal- 

 careous soils. These techniques are listed below in order of preference 

 (frequency of occurrence) : 



• Driving with impact hammer (driven piles) 



• Drilling and grouting (drilled and grouted piles) 



• Driving, drilling, and grouting combination 



• Drilling an enlarged base, then grouting (belled piles) 



• Driving with vibratory hammers 



Installing piles with an impact hammer is common because it is simple to 

 use and has been successfully used for a wide variety of soil conditions. 



Drilled and grouted piles are often used where rock layers and 

 highly cemented strata are present in the sediment profile and piles 

 cannot be driven to the final design penetration. In these cases, a 

 pile cavity is drilled to final penetration and then a pile is inserted 

 and grouted to form a composite pile. A drilled and grouted pile could 

 be used from the outset. Pile driving has caused significant degradation 

 of skin resistance in calcareous soils (Angemeer et al. , 1975). The 

 recently completed pile-supported POL pier at the Navy's Diego Garcia 

 Advance Base in the Indian Ocean used driven, open-end pipe piles in 



