Generally Pile foundation are provided where the hard strata
is at a great depth from the surface, where the surface soil
soil have poor bearing capacity.
Pile foundations are as follows...
1 end bearing pile foundation(in case of hard strata is
there but, not in greater depth.)
2 friction bearing pile(where friction material is available)
3 combined end bearing and friction bearing pile
4 tensile pile
5 compressive pile etc..
Other 2 may be..
1. pier foundation(for important structure) and 2. well