ITEC 250 test 2

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

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

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

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

Tiebacks

Piles may be made from

Timber b. Precast concrete c. Sitecast concrete d. Stone e. Steel

A slurry wall is a type of sheeting.

True

Bentonite clay makes an excellent waterproof membrane around a basement.

True

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.

True

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

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

why would you pressure treat wood?

combustibility decay

which material can withstand the strongest loads

concrete

bracing?

cross lot bracing, rakers, tiebacks

what would has naturally occurring decay resistant qualities?

cyprus, redwood, cedar

If Shallow foundations are less expensive, why don't we always use them?

depends on the soil type and use

foundation failures are usually a result of

differential settlement

soils are broken down into what two categories?

fine and course grain

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

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. 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.

why is wood laminated?

for size, strength and quality

the following picture is an illustration of what?

foundation failure

when laying a foundation topsoil is generally removed, why?

it can decay and cause differntial settlement

what are two types of sheeting?

soldier beam and lagging sheet piling slurry walls

how can you dewater a construction site?

sump pumps well-pointing water tight barrier

what are some different materials for piles

timber, steel (h type and pipe) concrete (precast & site cast)

why do we waterproof substructures and foundations

to help prevent erosion and corrosion

why is wood seasoned

to remove moisture strengthen stiffen easier to work with

what is the purpose of a foundation?

transfer the vertical load of a structure to the ground

what is the actual cross section dimension of a nominal 2x4 piece of lumber?

1 1/2 x 3 1/2

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

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.

what are the three different types of loads and foundation support?

1. dead load 2. live load 3. wind buoyancy etc.

what are some common uses of heavy timber?

200 + ft trusses interior columns domes arches

what size constitutes wood as " heavy timber"?

>5" nominal thickness

Under what conditions would you use a watertight barrier instead of well points when digging below 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.

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

All of the above.

What soil conditions favor the use of belled caissons?

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.

Which of the following are design thresholds that represent a major difference in the cost of a foundation

Building below the water table, Building close to an existing building, Going from shallow to deep foundations

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

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

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.

Which of the following are deep foundations:

Caisson, End-bearing pile, Friction pile

Which of the following are cohesive soils

Clay

what particular soil conditions favor the use of bell caissons

Cohesive soils

A tieback must always be anchored in rock.

False

A waterstop is used to lower the water table in the vicinity of a building

False

Combined footings are used to save money in cases where concrete prices are high.

False

Shallow footings may only be placed on undisturbed, natural soil.

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.

False

What measures can be taken to prevent its occurrence

Foundation must be safe so as not to result in collapse • Skyscraper must support a large building on a relatively narrow base • Settlement must not result in irreparable damage • Foundation must be feasible • Technically & economically • Constructability must adhere to surrounding environment

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

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

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

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

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

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