Fundamentals of Building Construction - Ch. 2 - Foundations

True

True or False: A slurry wall is a type of sheeting.

False

True or False: A tieback must always be anchored in rock.

False

True or False: A waterstop is used to lower the water table in the vicinity of a building.

True

True or False: Bentonite clay makes an excellent waterproof membrane around a basement.

False

True or False: Combined footings are used to save money in cases where concrete prices are high.

False

True or False: Shallow footings may only be placed on undisturbed, natural soil.

False

True or False: The foundation engineer need not be consulted by the architect and structural engineer until the size and position of the building on the land have been determined.

True

True or False: The soil around an excavation can sometimes be stabilized by reinforcing it.

True

True or False: Wood piles may be used without a decay-preventive treatment if they lie totally beneath the water table.

A watertight barrier is desirable in situations where lowering of the water table would have serious detrimental effects on neighboring buildings, and is possible in situations where the bottom edge of the barrier lies in an impermeable stratum of soil below the water table.

Under what conditions would you use a watertight barrier instead of well points when digging below the water table?

All of the above.

Underpinning may include which of the following foundation types: a. Wall and column footings b. Piles c. Mini-piles d. Caissons

The most common type of failure in foundations is differential settlement, in which overall settlement of the building is not excessive, but differences in the amount of settlement between different areas of the building cause failure of structural, cladding, or finish components of the building.

What is the nature of the most common type of foundation failure?

The pressure of the slurry against the walls of the trench prevents the walls from collapsing.

What is the purpose of the slurry used in the process of constructing a slurry wall?

Belled caissons are practical only where the bell can be excavated from a cohesive soil, and where the bearing stratum beneath the bottom of the caisson is impervious to the passage of water.

What soil conditions favor the use of belled caissons?

Tiebacks

When sheeting an excavation, which type of bracing is least obstructive to excavation operations?

C

Which of the following are cohesive soils: a. Cobbles b. Sand c. Clay d. Silt e. Peat f. Gravel

A, D, & F

Which of the following are deep foundations: a. Caisson b. Strip footing c. Rock anchor d. End-bearing pile e. Mat foundation f. Friction pile

A, D, & E

Which of the following are design thresholds that represent a major difference in the cost of a foundation? a. Building below the water table b. Building a slab on grade versus a crawlspace c. Using steel sheet piling versus concrete sheet piling d. Building close to an existing building e. Going from shallow to deep foundations

Precast concrete friction piles have the largest potential loadcarrying capacity, followed by steel pipe piles, steel Hpiles, and sitecast concrete piles.

Which type of friction piles can carry the heaviest load per pile?

If the soil beneath a foundation freezes, the foundation may be lifted by soil expansion or ice lenses.

Why is it necessary to carry shallow foundations below the frost line?

Fine sand consists of equidimensional particles that are large enough to behave as a particulate soil. Silt particles are also equidimensional but are much smaller, and silts are classified as fine-grained soils. Clay particles are even smaller than silt particles and are platelike rather than equidimensional. Unlike fine sand and silt, clay soils are governed in their properties by surface effects, and are therefore much more strongly affected by water content and the particular arrangement of particles in a given soil.

Explain in detail the differences among fine sand, silt, and clay, especially as they relate to the foundations of buildings.

Building code tables give approximate bearing values for soils. For a more accurate determination, various laboratory tests and on-site tests may be conducted.

How do we know how much foundation load a soil can carry?

By friction between the sides of the pile and the soil, by end bearing of the bottom of the pile against firm soil, or by both these means.

How does a driven pile transmit the load of a building into the soil?

We use deep foundations in situations where competent soil lies too far beneath the surface to be reached by shallow foundations.

If shallow foundations are substantially less costly than deep foundations, why do we use deep foundations?

Sheeting may be by means of soldier beams and lagging, sheet piling, or slurry wall.

List 3 different ways of sheeting an excavation. Under what circumstances would sheeting not be required?

1) Building below the water table. 2) Building close to an existing building. 3) Increasing the column or wall load from a building beyond what can be supported by a shallow foundation.

List and explain some cost thresholds frequently encountered in foundation design.

A, B, C, & E

Piles may be made from a. Timber b. Precast concrete c. Sitecast concrete d. Stone e. Steel f. Brick