Foundation Systems Quiz
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Questions and Answers

What is the main advantage of using concrete piles over wooden piles?

  • Lighter weight
  • Resistance to decay and marine worms (correct)
  • Lower initial cost
  • Easier installation

How far should a timber grillage be kept below the lowest recorded water line?

  • At least 2 inches
  • At least 1 foot
  • No specific requirement
  • Completely below (correct)

What type of concrete pile is generally molded before being driven?

  • Pre-cast pile (correct)
  • Timber pile
  • Plain concrete pile
  • Reinforced concrete pile

Why do wooden piles need to be cut off underwater?

<p>To avoid alternately wet and dry conditions (C)</p> Signup and view all the answers

What is typically placed between the driving block and the concrete in a driving head for pre-cast piles?

<p>A cushion of sand or rope (B)</p> Signup and view all the answers

What spacing is generally used for concrete piles?

<p>2 feet to 6 inches to 4 feet (A)</p> Signup and view all the answers

What component helps attach adjacent sticks in timber construction?

<p>Driftbolt (C)</p> Signup and view all the answers

What is a requirement for concrete piles when a steel casing surrounds them?

<p>Must extend at least 4 inches into the footing (B)</p> Signup and view all the answers

What primarily supports friction piles?

<p>Frictional resistance of surrounding earth mass (A)</p> Signup and view all the answers

What is the minimum diameter for wooden piles used in heavy buildings?

<p>8 inches (C)</p> Signup and view all the answers

What type of hammer is increasingly replacing the ordinary drop-hammer in pile driving?

<p>Steam hammer (B)</p> Signup and view all the answers

What is the main purpose of a mat foundation?

<p>To distribute loads evenly over low bearing capacity soil (A)</p> Signup and view all the answers

What is a key consideration when driving wooden piles?

<p>Keeping the piles plumb (D)</p> Signup and view all the answers

What is a key characteristic of steel grillage foundations?

<p>They involve the use of steel rails or beams. (D)</p> Signup and view all the answers

What occurs when a pile refuses to sink under several blows?

<p>The pile should be cut off and another one driven beside it (D)</p> Signup and view all the answers

Under what conditions are deep foundations typically used?

<p>When soil is unstable or has inadequate bearing capacity. (A)</p> Signup and view all the answers

When using a drop-hammer for driving piles, what should be the hammer's fall adjustment when penetration becomes small?

<p>Decrease to about 5 ft. (B)</p> Signup and view all the answers

What is the purpose of a pile cap in pile foundations?

<p>To connect and distribute the loads across multiple piles. (D)</p> Signup and view all the answers

What is characterized by the number of blows delivered by a steam hammer?

<p>60 to 70 blows per minute (D)</p> Signup and view all the answers

End bearing piles primarily rely on which type of support?

<p>The bearing resistance of soil or rock beneath them. (D)</p> Signup and view all the answers

What is the consequence of using excessive blows on a pile that has reached its limit of penetration?

<p>Crushing and splitting of the pile (A)</p> Signup and view all the answers

What minimum thickness of concrete is recommended beneath steel grillage foundations?

<p>6 inches (C)</p> Signup and view all the answers

Which of the following is NOT a type of deep foundation?

<p>Mat foundations (D)</p> Signup and view all the answers

What is a critical aspect of placing beams in a steel grillage foundation?

<p>The clear space between the flanges should not be less than 2 inches. (C)</p> Signup and view all the answers

What is a defining characteristic of cast-in-place piles?

<p>They are formed from hollow cylindrical steel tubes driven into the ground. (D)</p> Signup and view all the answers

Which type of cast-in-place pile is referred to as an 'uncased pile'?

<p>Simplex piles (A)</p> Signup and view all the answers

What distinguishes steel piles from other types of piles?

<p>They are concrete-filled steel pipes designed to bear on rock or hard pan. (C)</p> Signup and view all the answers

What method is used to form caissons?

<p>Boring with a large auger and filling the shaft with concrete. (B)</p> Signup and view all the answers

What is the typical diameter range of steel pipes used in steel piles?

<p>10 to 18 inches (C)</p> Signup and view all the answers

In the construction of a pedestal pile, what is done after the steel driving core is removed?

<p>Concrete is poured into the formed hole. (D)</p> Signup and view all the answers

Which statement is true regarding the driving process of steel piles?

<p>They can be driven in sections using steam-hammers. (D)</p> Signup and view all the answers

What is a common element in the composition of all types of cast-in-place piles?

<p>Inclusion of some form of concrete. (B)</p> Signup and view all the answers

What is the primary function of a foundation system in construction?

<p>To transfer lateral loads to the ground (C)</p> Signup and view all the answers

Which type of foundation is best suited for stable soil located near the ground surface?

<p>Shallow or spread foundations (D)</p> Signup and view all the answers

What distinguishes individual or isolated footings from other types of foundations?

<p>They support free standing columns and piers (B)</p> Signup and view all the answers

What purpose do combined foundations serve?

<p>To support two or more columns where individual footings cannot be centered (A)</p> Signup and view all the answers

What is a key characteristic of cantilevered footings?

<p>They connect multiple columns with a tie-beam or strap (A)</p> Signup and view all the answers

Continuous footings can serve which of the following functions?

<p>Supporting a row of columns or all columns by strips at right angles (C)</p> Signup and view all the answers

What design consideration is crucial for combined column footings?

<p>The center of gravity of the loads must align with the center of gravity of the footing area (D)</p> Signup and view all the answers

What defines the primary use of strip footings in construction?

<p>They are continuous spread footings supporting foundation walls (A)</p> Signup and view all the answers

What is the purpose of the iron pile ring?

<p>To prevent the pile from splitting (A)</p> Signup and view all the answers

In which soil condition do piles drive better with a square point?

<p>When driven in soft and silty soils (A)</p> Signup and view all the answers

What is the usual spacing requirement for driving piles?

<p>At least 2 ft on centers (A)</p> Signup and view all the answers

What is the maximum allowable load on wood piles?

<p>20 tons (D)</p> Signup and view all the answers

What type of cap is usually preferred for piles and how thick is it typically?

<p>Reinforced concrete cap, usually 18 inches or more in thickness (A)</p> Signup and view all the answers

What should be done to piles that will be driven in or exposed to salt water?

<p>Treat them with creosote, dead oil, or coal-tar (A)</p> Signup and view all the answers

When capping piles with timber grillages, what is the minimum cross-section size for the timbers?

<p>10” x 10” (B)</p> Signup and view all the answers

What may happen if long piles are driven closer than 2 ft on centers?

<p>They may force each other up from their solid bed (D)</p> Signup and view all the answers

Flashcards

Shallow Foundation

A type of foundation system that transfers loads to the soil relatively close to the ground surface.

Isolated Footing

A shallow foundation supporting a single column or pier.

Strip Footing

A continuous shallow foundation that supports a foundation wall.

Combined Footing

A shallow foundation supporting two or more columns, used when individual footings aren't possible.

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Cantilevered Footing

A type of combined footing where exterior and interior columns are connected by a tie-beam or strap.

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Continuous Footing

A shallow footing that supports a line of columns or building columns in strips at right angles to each other.

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Deep Foundation

A foundation system that transfers loads to soil located at a greater depth.

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Mat Foundation

A foundation type used on soil with low bearing power, where unequal settlement is a concern. All parts are interconnected to act as a single unit, ensuring stability.

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Steel Grillage Foundation

A foundation type using steel beams to distribute load over a wide area, avoiding extensive excavation. Beams rest on a concrete layer and are grouted for even bearing.

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Deep Foundation

A foundation system transferring loads to stable soil strata below unstable soil layers.

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Pile Foundation

A deep foundation using piles, pile caps, and tie beams to transfer load to a suitable bearing stratum.

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Pile Cap

A slab or beam covering the head of multiple piles, transferring and distributing loads.

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End Bearing Piles

Piles supported primarily by the bearing resistance of the underlying soil or rock.

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Friction piles

Friction piles rely on friction between the pile and soil for support, rather than the load-bearing capacity of the soil beneath.

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Skin friction

Skin friction is the frictional resistance between a pile and the surrounding soil.

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Wood piles

Wooden piles are used as a foundation, especially in areas with compressible, water-saturated soil.

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Pile driving methods

Driving piles involves using tools like drop hammers and steam hammers to push the piles into the ground.

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Drop hammer

A type of pile-driving tool that uses gravity to drive the pile.

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Steam hammer

A type of pile-driving tool that uses steam to drive the pile with more rapid blows compared to a drop hammer

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Pile Depth and Penetration

The depth of a pile depends on the type of soil and the anticipated load. Penetration should be monitored and stopped to avoid damage to the pile.

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Pile refusal

Pile refusal occurs when a pile resists sinking further despite repeated blows after reaching a specified depth.

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Pile cutting

If a pile refuses to sink further, it can need to be cut off and replaced with another pile.

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Pile Ring

A steel band encircling a timber pile head to prevent splitting during driving.

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Pile Point (Soft Soil)

Square-shaped pile point used for driving piles in soft and silty soils.

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Pile Point (Compact Soil)

Iron or steel conical point shod on pile ends for compact soils.

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Saltwater Pile Protection

Piles exposed to salt water need creosote, dead oil, or coal-tar treatment to prevent shipworm damage.

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Pile Spacing

Piles should not be closer than 2 feet on centers to avoid forcing each other up.

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Maximum Load (Wood Pile)

Maximum safe load on a wood pile is typically 20 tons.

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Pile Top Cut-off

Cut the pile top to the minimum water level to prevent decay.

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Pile Cap Material

Reinforced concrete is often used to cap piles.

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Grillage Pile Cap

Heavy timber grid for supporting pile loads; bolted to pile top.

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Timber Grillage

A timber framework used to distribute load on piles, improving stability.

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Timber Grillage Placement

Timber grillages must be placed below the lowest water level to prevent rot and settling.

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Concrete Piles

Strong, durable foundations that can be reinforced and used in areas with or without access to water.

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Concrete Pile Advantages

Resistant to decay and marine worms, ideal for foundations that may be in wet conditions.

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Reinforced Concrete Piles

Concrete piles strengthened with steel bars for added strength, commonly used.

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Reinforced-Concrete Pile Types

Reinforced concrete piles can be cast in place or pre-cast

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Pre-cast Piles

Concrete piles formed in a yard or site, allowed to cure for a period before use in a foundation.

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Pile Driving Cushion

A layer of sand, rope, or similar material placed between the pile-driving head and the pile to prevent crushing during installation.

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Driftbolt

A short rod used to attach timber elements (e.g., adjacent timbers, timber to piles).

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Cast-in-place piles

Piles constructed directly in the ground, often reinforced.

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Cased pile

A pile method using a steel tube; concrete fills the space after the core is removed.

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Uncased pile

A pile method where a steel tube is driven into the ground, and concrete is poured in as the tube is pulled out.

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Pedestal pile

A pile where concrete is forced into the surrounding soil using pressure as the core is removed.

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Steel piles

Concrete-filled steel pipes bearing on rock or hardpan.

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Caisson foundations

Cast-in-place concrete piers made by boring or excavating a shaft.

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Pile Driving Methods

Process of using tools like drop or steam hammers to insert piles into the ground.

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Drop hammer

Pile driving tool using gravity to impact the pile.

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Steam hammer

Pile driving tool using steam to impact the pile.

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Study Notes

Foundation Systems

  • Foundation systems transfer loads from structures to the ground.
  • Two main types: shallow and deep foundations.

Shallow Foundations

  • Used when stable soil with adequate bearing capacity exists near the surface.
  • Transfer loads directly to supporting soil.
  • Types include:
    • Individual/isolated footings:
      • Block or square footings
      • Stepped footings
      • Slope or pyramidal footings
    • Strip footings: continuous footings for foundation walls. Can be stepped to accommodate sloping grades.
    • Combined footings: support two or more columns. Designed so the center of gravity of the footing area coincides with the combined loads.
    • Cantilevered footings: connect exterior and interior columns with a tie-beam or strap. The strap sits level with the top of footings.
    • Continuous footings:
      • Support a line of columns.
      • Support all columns with strips at right angles to each other.
      • Can also be inverted slab or inverted tee continuous footings.
    • Mat/raft foundations: used when the soil has low bearing power and unequal settlement is a concern. All parts of the foundation are interconnected to act as one. Types include:
      • Flat slabs of plain or reinforced concrete.
      • Beams or girders with a slab underneath.
      • Beams or girders with a slab on top.

Deep Foundations

  • Used when the soil underlying a shallow foundation is unstable or inadequate.
  • Transfer loads to a more stable stratum (rock or dense material) below the superstructure.
  • Types include:

    • Pile foundations:

      • System of end-bearing or friction piles, pile caps, and tie beams to transfer loads.
      • End bearing piles: depend on soil/rock resistance.
      • Friction piles: depend on friction between the pile and soil.
      • Wood piles: made from tree trunks. Driven by a drop-hammer or steam-hammer.
      • Concrete piles: molded in place or pre-cast. Used on land or in water. Preferable to wooden piles if the area is prone to water damage.

    • Steel grillage foundations: use steel rails or beams to distribute load over a wide area for a minimum of depth, usually when excavation should be avoided.

    • Caisson foundations: cast-in-place concrete pier formed by boring, usually with a large auger or excavating a shaft. May also be called drilled piles or piers. Rock caissons use an H-section core within the concrete.

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Description

Test your knowledge on foundation systems, focusing specifically on shallow foundations. This quiz covers different types of shallow foundations, their purposes, and characteristics. Understand how different footings work to transfer loads from structures to the ground.

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