DEEP FOUNDATIONS – PART I

1. DEEP FOUNDATIONS – PART I M. Zoghi, Ph.D., P.E. Geotechnical Design Fall 2007

2. Outline Significance Types Load Transfer Mechanism Single Pile Capacity Examples

3. I. Significance Highly compressible and too weak Highly compressible and too weak End-Bearing Pile Friction Pile Laterally-Loaded Pile

4. Expansive and Collapsible Soils Transmission Towers, Offshore Platforms, etc. Subjected to Uplifting Force Bridge Abutments Supported via Piles and Piers – to Avoid Scouring!

5. II. Types Steel H-piles Steel pipe-piles Cast-in-situ concrete piles Precast concrete piles Prestressed concrete piles Auger-cast piles Timber piles

6. H-Piles Steel H-Piles Advantages * High individual load capacity when driven to practical refusal. * Readily available. * Easily shortened or extended. * Can be installed with conventional driving equipment. * Minimal disturbance to adjacent piles or structures. * Easily driven through dense granular soil or very stiff clays. * Reduced soil heave and ground vibrations. * Excellent penetrating capability. * High lateral capacity. * High uplift capacity. Disadvantages * Higher cost if lightly loaded. * Tend to drive deeper in loose sands and silty sand. * Post driving visual inspection not possible. * Maintaining fixed web orientation for lateral loading. General * Common splices involve full penetration butt weld. * Most efficient when driven through deep soft to medium stiff clays to refusal on rock. * Propriety splicers available. * Toe reinforcing may be required in areas of dense soil, soil containing boulders or rock, or when driven to sloping rock. * Cathodic or other protection may be required.

7. Splice of H-pile by welding Splice of pipe pile by welding Splicing by riveting

8. Pipe Piles Flat-Driving Point of Pipe Pile Conical Driving Point Pipe Pile

9. Precast Concrete Piles Precast piles with ordinary reinforcement

10. Cast-in-place concrete piles

11. Timber Piles Splicing of timber piles: (a) via pipe sleeves; (b) via metal straps

12. III. Load-Transfer Mechanism

13. IV. Single Pile Capacity

15. α-Method