Chapter 2 - Notes

Question 1

What are four foundation requirements?

Answer 1

1. Must transmit building loads to the rock or soil on which it rests
2. Must not fail, resulting in collapse.
3. Must not settle so much as to damage structure or impair function.
4. Muse be economically and technically feasible.

Question 2

What are dead loads?

Answer 2

The combined weight of all the permanent components of the building - frame, floors, roofs, walls, equipment, etc.

Question 3

What are live loads?

Answer 3

Nonpermanent loads caused by the weights of building’s occupants, furnishings, and movable equipment.

Question 4

What is uniform settlement?

Answer 4

Settling that occurs at roughly the same rate throughout the building. All buildings settle.

Question 5

What is differential settlement?

Answer 5

Settling that occurs at different parts of the building at different rates. Can lead to distortion of frame, sloped floors, cracked walls, or inoperable doors.

Question 6

What are coarse-grained soils?

Answer 6

Gravel and sand. They don’t stick together when wet (cohesionless) and when unconfined, have little strength. They are little affected by moisture content and drain well.

Question 7

What are fine-grained soils?

Answer 7

Silts and clays. They have varying degrees of cohesiveness and drainage.

Question 8

What are highly organic soils?

Answer 8

Peat, much, topsoil, etc. Not suitable for building foundations.

Question 9

What is shear strength?

Answer 9

Resistance to internal sliding caused by friction between particles that keep the particles from sliding past one another.

Question 10

What is soil liquefaction?

Answer 10

When water-saturated sand or silts lose virtually all of their strength and behave as a liquid when subjected to sudden, large changes in loads.

Question 11

What is the strongest material to found a building on?

Answer 11

Consolidated rock. But usually, such rock is too deep to reach economically.

Question 12

Why are the largest buildings in NYC in Manhattan?

Answer 12

The island’s bedrock is closest to the surface in Manhattan.

Question 13

What is the water table?

Answer 13

The water table is the elevation at which the soil is normally fully saturated.

Question 14

What is the frost line?

Answer 14

The level to which the ground freezes in winter. Footings must be placed below it.

Question 15

What is the angle of repose?

Answer 15

If a construction site is sufficiently larger than the area to be covered by the building, the edges of the excavation can be sloped back or benched at a low enough angle that the soil will not slide back into the hole. This angle is called the max allowable slope or angle of repose.

Question 16

What is dewatering?

Answer 16

The removal of water from an excavation or surrounding soil.

Question 17

What are well points?

Answer 17

Vertical pipes inserted into the ground around the excavation perimeter that suck up water to depress the water table and dewater the site.

Question 18

What is used to dewater when well points could adversely affect other buildings?

Answer 18

Watertight barriers made from a slurry wall or soil-mixed wall that prevent water from reaching an excavation.

Question 19

Buildings are comprised of what three main parts?

Answer 19

Superstructure, substructure, and foundations.

Question 20

What is a building superstructure?

Answer 20

The above-ground portion of a building.

Question 21

What is a building substructure?

Answer 21

The habitable portion located below the ground.

Question 22

What are building foundations?

Answer 22

The below-ground components of the building devoted solely to the transfer of loads into the soil.

Question 23

What are shallow foundations?

Answer 23

Foundations that transfer building loads to the earth close to the base of the substructure.

Question 24

What are deep foundations?

Answer 24

Foundations that extend downward through layers of weak or unstable strata to reach more competent soil or rock deeper within the earth.

Question 25

What are spread footings?

Answer 25

Footings that take concentrated loads from above and spread them out across an area of soil large enough that the allowable soil pressure is not exceeded.

Question 26

What are column footings?

Answer 26

Square blocks of concrete that distribute a column load to the soil below.

Question 27

What are wall footings?

Answer 27

Continuous strips of concrete that distribute a load-bearing wall’s loads to the soil below.

Question 28

What are the three types of shallow foundations?

Answer 28

Slab-on-grade, crawlspace, and basement.

Question 29

What’s a slab-on-grade foundation?

Answer 29

A concrete slab placed directly on the ground that can function as simple, inexpensive spread footings for one- and two-story buildings in climates with little or no ground freezing.

Question 30

What is a crawlspace?

Answer 30

Space under a raised floor structure that gives easier access to underfloor piping and wiring than a slab on grade.

Question 31

What is a caisson (drilled pier)?

Answer 31

A concrete cylinder poured into drilled holes for deep foundations. Similar to a column footing but it extends through strata of unsatisfactory soil beneath the substructure of a building until it reaches suitable stratum.

Question 32

What are Piles?

Answer 32

Concrete cylinders that are more slender than caissons, and are forcibly driven into the earth rather than drilled and poured. Used where non-cohesive soils or subsurface water makes caissons impractical. End bearing piles hit firm resistance from suitable stratum. Friction piles can’t reach that layer and rely on friction instead.

Question 33

What’s a pile cap?

Answer 33

Piles are usually driven closely together in clusters of 2 to 25 piles each. A pile cap connects each cluster, distributing the load of the column or wall evenly.

Question 34

What is a grade beam?

Answer 34

Reinforced concrete beams constructed between pile caps to transmit the wall loads to the piles. Also used with caisson foundations.

Question 35

What is underpinning?

Answer 35

The strengthening and stabilizing of an existing foundation.

Question 36

What is damp-proofing?

Answer 36

A moisture-resistant cement plaster or asphalt compound applied to basement walls where groundwater conditions are mild or waterproofing requirements are not critical.

Question 37

What is waterproofing?

Answer 37

Materials that resist the passage of water even under demanding condition of hydrostatic pressure.

Question 38

What is the purpose of a retaining wall?

Answer 38

To hold back soil where an abrupt change in ground elevation occurs. It must resist the pressure of the earth and groundwater that presses against it.

Question 39

What is backfilling?

Answer 39

The replacement of soil materials in an excavation to restore it close to its finished level. Occurs around foundations and substructures, in utility trenches, and behind retaining walls.