Reason to Pull out the Existing Piles
The piles may have to be pulled out under following reasons or circumstances:
- If the pile becomes damaged during driving operation.
- To remove the pile which are temporarily driven, as in case of cofferdams.
- Sometimes piles are driven to check the bearing power of the underground soil, After performing the test it needs to be withdrawn.
- When old structure standing on the piles, and it needs to be demolished.
Methods for Pulling out the Existing Piles
The method of withdrawing piles depends on the type of pile, techniques and availability of equipment. Concrete piles, particularly uncased concrete piles, cannot be pulled out without damage. Whereas cased concrete piles and steel piles can be withdrawn without damage, therefore, it can be reused.
Double-acting steam hammer
The double-acting hammer is worked in a reverse direction together with a constant pull of 4 N/mm2 on the pile helps extract it.
Special pile extractors
They are special equipment which can be used for withdrawal of piles. They do not require any special fittings for extraction.
Vibrators loosen the surrounding soil and thus make piles loose which can be easily pulled out using specially designed tongs.
Use of Direct Electric Current
When direct current is passed through the steel pile, water present in the surrounding gets attracted towards the pile and lubricates its surface. This will practically eliminate the skin friction and pile can be easily pulled out. This method is mostly applied in case of steel piles.