Module 5 :
Design of Deep Foundations
Lecture 20 : Introduction
[ Section 20.2 :
Design Methodology For Piles
]
POINTS TO BE CONSIDERED FOR CHOOSING PILES
Loose cohesion less soil develops much greater shaft bearing capacities if driven large displacement piles are used.
Displacement effect enhanced by tapered shafts.
Potential increased of shaft capacities is undesirable if negative friction is to be feared. (Negative friction is also called drag down force)
High displacement piles are undesirable in stiff cohesive soils, otherwise excessive heaving takes place.
Encountered with high artesian pressures on cased piles should be excluded. (Mainly for bridges and underwater construction)
Driven piles are undesirable due to noise, damage caused by vibration, ground heaving.
Heavy structures with large reactions require high capacity piles and small diameter cast-in-situ piles are inadequate.
PILE CLASSIFICATION
Friction piles.
End bearing piles.
Compaction piles.( Used for ground movement, not for load bearing )
Tension piles/Anchored piles.(To resist upliftment)
Butter piles (Inclined) --- +ve and –ve.
Fig. 5.1 Direction of load is same as the direction of batter. (Rotation of pile)
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