1. Foundations
Purpose – To transfer weight of structure (including live loads) to the ground within allowable settlement criteria

2. Foundation Failure
Leaning Tower of Pisa

3. Foundation Shape & Size
Dependant on type of structure, weight, soil bearing capacity & sensitivity of structure
Pressure under foundation
= structure weight + imposed loads
area of foundation * F.O.S
Note effect of wind or horizontal loading

4. Mass Concrete Pile Cap

5. Reinforced Concrete Pile Cap

6. Types of Bearing Pile
Displacement
Replacement
Driven cast
Supported
Unsupported
insitu
Permanent
Permanent
Temporary
casing
casing
Temporary
Pre-Formed
support
Drilling mud
Concrete
Timber
Steel
Casing
Or water

7. Driven Cast Insitu
No soil removed
Can cause vibration and noise

8. Driven Cast Insitu Pile Rig

9. Driven Piles

10. Replacement - Rotary Bored Piling
300mm to 2400mm diameter
Up to 50M depth
Auger ‘screws’ into ground, breaking up soil
Auger withdrawn with soil
Back spun to release
May require temporary casing

11. Continuous Flight Auger (CFA)
Auger not removed during drilling – supports bore sides
When design depth reached concrete delivered through centre of auger to base of bore and auger removed at same rate as concrete infill
Reinforcement cage added to wet concrete
Quiet
Excavated soil to be disposed of

12. Continuous Flight Auger (CFA)

13. CFA Piling

14. Auger Pile Walling 1. Contiguous Piling – small gap between piles
2. Secant Piling – piles interlocked
Non Reinforced
Reinforced

15. Contiguous Pile Wall (with capping beam)

16. Vibro Replacement
1. Vibrator penetrates weak soils under action of vibrations and 'compressed air' jetting medium and forms a hole to design
2. After being held at depth for a short time, the vibrator is withdrawn and a charge of stone is placed into the hole.
3. The vibrator is reintroduced into the hole, the stone is compacted, forced out and tightly interlocked with the surrounding ground.
4. by adding successive charges of stone and compacting each one, a column of very compact stone is built up to ground level.

17. Vibro Replacement

18. Dynamic Deep Compaction
With DDC, the ground is subjected to repeated surface tamping using a heavy steel and concrete weight.
Typically the tamper weighs between 5 and 20 tonnes, dropping in free fall from heights of up to 25 metres.
The tamper is dropped a set number of times on a grid pattern over the site to form a pass. Two to five passes on a site, dependent on soil type and condition, can be required.
The imprints formed at each drop position are infilled with granular material after each pass.

19. Dynamic Deep Compaction

20. Health & Safety Issues Heavy plant manoeuvring on site – use banksman
Other plant eg concrete deliveries need to work close by
Overhead working on many applications
Noise of driven piles
Deep excavations to be protected
Piles designed on basis of site investigation

21. Environmental Issues
Noise from driven piles – ear protectors, neighbours
Vibration from driven piles
Removal of excavated material from replacement piling
Protection of groundwater, particularly drilling mud (bentonite)
Diesel storage