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In normal practice, reliance is placed on the self-compaction of specially designed concrete mixes to achieve adequate compaction. The use of vibrating devices like poker vibrators is seldom adopted for the compaction of concrete piles.
In fact, other than the consideration of the impracticality in using vibrating device in long piles, there is serious concern about the possible occurrence of aggregate interlock which poses difficulty during casing extraction. In the worst scenarios, the temporary casings together with reinforcement cages are extracted during the lifting up of pile casings. This is another reason which accounts for not using vibrating machines for piles with casing extraction.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.