Foundation systems
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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.

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Foundation Systems

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Foundation systems

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.


Foundation systems1

Foundation Systems

Spread Footing

Piles

Piers or Caissons


Spread footings

Spread Footings

Spread Footing Options


Foundation systems2

Foundation Systems

Spread Footing

Piles

Piers or Caissons


Piles

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.


Types of piles

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


Foundation systems3

Foundation Systems

Spread Footing

Piles

Piers or Caissons


Timber piles

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


Timber piles1

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


Concrete precast piles

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


Cast in place concrete piles

Cast-in-Place Concrete Piles


Cast in place concrete piles1

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


Steel piles

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


Bulb piles

Bulb Piles

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


Pile hammers

Pile Hammers

  • Drop

  • Steam or compressed air

  • Diesel

  • Hydraulic

  • Vibratory


Drop hammer pile driver

Drop Hammer Pile Driver


Drop hammer

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


Steam air hammer

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


Steam air hammer1

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


Diesel hammer

Diesel Hammer


Diesel hammer operations

Diesel Hammer Operations

http://www.youtube.com/watch?v=ElBGcYhdjMA


Diesel hammer1

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


Vibratory driver

Vibratory Driver


Vibratory hammers

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


Determining pile load capacity

Determining Pile Load Capacity

Wr – wt. of hammer ram

Wp – wt. of pile, including driving equipment


Piers caissons

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.


Pier installation

Pier Installation


Rock anchors

Rock Anchors


Rock anchors1

Rock Anchors


Rock anchors2

Rock Anchors


Slope failure cohesionless soil

Slope Failure Cohesionless Soil

Profile Before Failure

Profile After Failure

Angle of Repose


Slope failure cohesive soil

Slope Failure Cohesive Soil

Profile Before Failure

Profile After Failure

Slip Plane


Subsidence or bulging

Subsidence or Bulging

Subsidence

Bulge


Tension crack

Tension Crack

Tension

Crack


Embankment failure modes

Embankment Failure Modes

Profile

Before

Failure

Profile

Before

Failure

Slide

Mass


Trench cave ins

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.


Protecting excavations workers

Protecting Excavations & Workers

  • Sloping & Benching

  • Shoring & Shielding


Osha soil classification

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


Osha maximum allowable slopes for excavation sides

OSHA Maximum Allowable Slopes for Excavation Sides

Always Check 29 CFR 1926 Subpart P Appendix B for updates – www.OSHA.gov


Type a soil

Type A Soil


Varying soils

Varying Soils


Metal shoring system

Metal Shoring System


Trench shield

TrenchShield


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