In water bearing ground, some water head (about 1 m) above the existing ground water table is maintained to stabilize the bore during excavation below casings by pumping water to the pile bore.
This balanced head condition is created to minimize the possible drawdown of surrounding water table which may affect the stability of nearby structures. Moreover, this helps to limit the possible inflow of water by piping from the base of pile bore.
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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.
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