function of a pile foundation

Describe the main function of a pile foundation.
2. Piles are made out of different materials. List the major advantages and disadvantages of prestressed concrete piles.
3. Use the Web to investigate the advantages and disadvantages of using a cable-operated drop hammer to drive piles.
4. Use the Web to investigate the advantages and disadvantages of using a single-acting hammer (air or steam) to drive piles.