Foundation Systems

1. Foundation Systems • The Foundation of a structure supports the weight of the structure and all applied loads. • Includes the soil or rock upon which the structure is placed, as well as, the structural system designed to transmit the loading to this supporting soil or rock. • Foundation failure is the collapse or excessive settlement of the supporting structure.

2. Foundation Systems Spread Footing Piles Piers or Caissons

3. Spread Footings Spread Footing Options

4. Foundation Systems Spread Footing Piles Piers or Caissons

5. Piles • A Pile is a column driven into the soil to support a structure by transferring building loads to a deeper and stronger layer of soil or rock.

6. Timber Piles Untreated Treated with a preservative Concrete Precast Concrete Piles Cast-In-Place Concrete Piles Steel Piles Bulb Piles~ Franki Piles Composite Piles ~ Concrete & Steel Plastic with steel pipe core Types of Piles

7. Foundation Systems Spread Footing Piles Piers or Caissons

8. Advantages: More popular lengths and sizes are available on short notice Economical in cost They are handled easily, with little danger of breakage After driving, they can be easily cut to any desired length Can be extracted easily if needed Disadvantages May be difficult to obtain piles sufficiently long and straight Can be difficult or impossible to use in hard formations Difficult to splice Usually not suitable to use as end-bearing piles – better for friction bearing piles Usually require treatment with preservatives to maintain structural capacity over required duration – possible environmental impact. Timber Piles

10. Advantages: More popular lengths and sizes are available on short notice Economical in cost They are handled easily, with little danger of breakage After driving, they can be easily cut to any desired length Can be extracted easily if needed Disadvantages May be difficult to obtain piles sufficiently long and straight Can be difficult or impossible to use in hard formations Difficult to splice Usually not suitable to use as end-bearing piles – better for friction bearing piles Usually require treatment with preservatives to maintain structural capacity over required duration – possible environmental impact. Timber Piles

11. Advantages: Have high resistance to chemical and biological attacks Have high load-carrying capacity Disadvantages Difficult to reduce or increase the length Large sizes require heavy and expensive handling and driving equipment Inability to quickly obtain piles may delay the starting of a project Possible breakage of piles during handling or driving produces a delay hazard Concrete Precast Piles

12. Cast-in-Place Concrete Piles

13. Advantages: Noise levels during construction are minimized Little to no detrimental vibration to adjacent structures during construction Can be installed in areas w/ low overhead restrictions and minimum clearance Pile splicing is eliminated Disadvantages Require careful placement of the concrete to ensure a structurally sound shaft Soil and groundwater conditions can affect installation times and cost Due to construction technique, no penetration resistance correlation can be made about pile capacity Instances where uplift forces can be encountered requires installation of reinforcing steel, which can be difficult Cast-in-Place Concrete Piles

14. Steel Piles • Probably the best for deep, deep depths • Can be easily cut and spliced. • Most common shapes are: • Steel H Sections • Steel-Pipe Piles

15. Bulb Piles A.k.a compacted concrete piles, Franki piles, and pressure injected footings

16. Pile Hammers • Drop • Steam or compressed air • Diesel • Hydraulic • Vibratory

17. Drop Hammer Pile Driver

18. Advantages Small investment in equipment Simplicity of operation Ability to vary energy per blow by varying the height of fall Disadvantages Slow rate of driving piles Danger of damaging piles by lifting hammer too high Danger of damaging adjacent buildings as a result of the heavy vibration caused by a hammer Unable to use directly for underwater driving Drop Hammer

19. Steam/Air Hammer • Uses a freely falling weight that is lifted by steam or compressed air • Length of the stroke and energy per blow may be decreased by reducing the steam or air pressure

20. Advantages Greater # of blows per minute permits faster driving Reduction in the velocity of the ram decreases the danger of damage to piles during driving Enclosed types may be used for underwater driving Disadvantages Require more investment in equipment They are more complicated, with higher maintenance cost Require more time to set up and take down Require a large crew to operate equipment Require a crane with a greater lifting capacity Steam/Air Hammer

21. Diesel Hammer

22. Diesel Hammer Operations http://www.youtube.com/watch?v=ElBGcYhdjMA

23. Advantages Requires no external source of energy – more mobile Economical to operate – fuel consumption for a 24,000 ft-lb hammer is 3 gal per hour Convenient for remote areas – not necessary to provide a boiler, water for steam. Operates well in cold areas Hammer is light in weight compared to a steam hammer of equal rating Energy per blow increases as driving resistance increases Disadvantages Difficult to determine the energy per blow since it depends on driving resistance May not operate well in soft ground conditions – pile has to offer sufficient driving resistance to activate the ram Number of strokes per minute is typically less than for a steam hammer Length of a diesel hammer is slightly greater that the length of a steam hammer Diesel Hammer

24. Vibratory Driver

25. Vibratory Hammers • Especially effective when piles are driven into water-saturated noncohesive soils • May be problematic to use to drive piles into dry sand or into cohesive soils that do not respond to the vibrations. http://www.youtube.com/watch?v=OUHE7mRPFQI

26. Determining Pile Load Capacity Wr – wt. of hammer ram Wp – wt. of pile, including driving equipment

27. Piers & Caissons • A pier is a reinforced concrete column constructed below the ground surface to transfer the load of a structure down to a stronger rock or soil layer. • A caisson is a structure to provide lateral support to an excavation. • Can be open or closed (pneumatic). • Drilled piers are piles that are built In holes drilled into the soil. • Cohesive soil usually does not need a lining.

28. Pier Installation

29. Rock Anchors

30. Rock Anchors

31. Rock Anchors

32. Slope Failure Cohesionless Soil Profile Before Failure Profile After Failure Angle of Repose

33. Slope Failure Cohesive Soil Profile Before Failure Profile After Failure Slip Plane

34. Subsidence or Bulging Subsidence Bulge

35. Tension Crack Tension Crack

36. Embankment Failure Modes Profile Before Failure Profile Before Failure Slide Mass

37. Trench Cave-ins • Many trenching fatalities occur in relatively shallow trenches – less than 10 feet deep. • Fatalities generally occur when a worker is knocked down by a trench wall collapse and subsequently buried by another collapse. • Recovery attempts are typically futile • Cause of death is typically due to crushing rather than asphyxiation.

38. Protecting Excavations & Workers • Sloping & Benching • Shoring & Shielding

39. OSHA Soil Classification • Type A – e.g. Clay, silty clay, sandy clay • Type B – e.g. Silt, loam • Type C – e.g. Granular soils, sand

40. OSHA Maximum Allowable Slopes for Excavation Sides Always Check 29 CFR 1926 Subpart P Appendix B for updates – www.OSHA.gov

41. Type A Soil

42. Varying Soils

43. Metal Shoring System

44. TrenchShield