In current practice concrete cover is usually provided at the pile tips of pre-bored H-piles socketed in rock. The purpose of such arrangement is to avoid the potential occurrence of corrosion to H-piles in case concrete cover is not designed at pile tips. However, recent field and laboratory observations had reservation of this viewpoint.
In case H-piles are designed to be placed directly on top of rock surface, it provides the tip resistance to limit the pile movement in the event of bond rupture between grout and H-piles. As such, some contractors may choose to tamp the H-piles by using drop hammers to ensure the H-piles are founded directly on top of rock surface. Practically speaking, it poses difficulties during the process of tamping because there is a chance of possible buckling of long H-piles when too much energy is provided to the piles.
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.
If you have a query, you can ask a question here.