6 Foundations

Question 1

Strata

Answer 1

Identifiable layers of different soils

Question 2

Soil type affects the type of building that can be built. Allowable foundation pressure for sandy clay is

Answer 2

1,500 lbs/ft2

Question 3

For bedrock, allowable foundation pressure

Answer 3

12,000 lbs ft2

Question 4

Approximate depth of test soil pits

Answer 4

8 ft

Question 5

Highrise may require a foundation depth of

Answer 5

100 ft

Question 6

Foundations must resist these types of loads

Answer 6

Wind loads, lateral or uplifting forces
Soil pressure 
Uplifting forces from ground water
Thrusts from arch supports, domes or vaults. 
Seismic forces

Question 7

Footing

Answer 7

Part of foundation that rests off bearing soil and is wider than wall of foundation.

Question 8

Main contributors to type of foundation are structural config and soil conditions. Others are

Answer 8

Available work space
Environmental factors.
Impact on adjacent properties
Building code and regulations.

Question 9

Foundations are divided into two types

Answer 9

Shallow and deep

Question 10

Shallow foundation

Answer 10

Transfers the weight of the building to slim and base of building. For use when shallow soil can support weight of building.

Question 11

Deep foundations.

Answer 11

Penetrate soil deeps to reach more stable soil beds

Question 12

Shallow foundations usually make use of what to transmit load to soil

Answer 12

Footings

Question 13

Wall footing

Answer 13

Counting pus strip of concrete that supports a wall

Question 14

Wall footings can take several forms :

Answer 14

Monolithic floor, increased thickness of floor slab at edges
Widened strip of concrete under a wall that supports raised floor with crawl space.
Widened strip of concrete under full story high walls that create a full or partial basement.

Question 15

Column footing

Answer 15

Square pad of concrete that supports a column

Question 16

Grillage footing

Answer 16

Footing that consists of beams placed at right angles to each other and usually encased in concrete.

Question 17

Mat foundation

Answer 17

Thick slab beneath the entire area of a building. Mat is different than slab in thickness and reinforcement.

Question 18

Floating foundations

Answer 18

Volume of soil removed from foundation space is approximately equal to weight of building supported, minimizing settling. Used in some situations where soil strength is low.

Question 19

Depending on composition and density of soil, and building construction, 1 story of soil can equal

Answer 19

5-8 stories of building

Question 20

Piles

Answer 20

Used to support loads. Likes are driven into the ground and develop the load carrying ability either through friction, or being in contact with rock or load bearing soil.

Question 21

Pier

Answer 21

Load supporting member constructed by drilling or digging shaft then filling with concrete.

Question 22

Deep foundations take the form of either

Answer 22

Piles or piers

Question 23

A pier designed with a footing is known as

Answer 23

A belled pier

Question 24

Piers are sometimes referred to as caissons. A caisson is actually

Answer 24

The protective sleeve used to keep water out of excavation for pier.

Question 25

On a hill, the foundation vertical elements are connected with

Answer 25

A tie beam. Intended to resist lateral force of building on the hill.

Question 26

Cracks in concrete foundation walls often develop but are

Answer 26

Don’t usually affect the ability of the wall to support or distribute load. Cracks must be inspected however to ensure they don’t worsen.

Question 27

For a foundation. Expanded polystyrene foam EPS can be used

Answer 27

Outside the foundation as insulation.

Question 28

Building settlement may be minor or structurally severe. Moving the building in what directions

Answer 28

Downward, settling
Upward, heaving
Outward, lateral displacement.

Question 29

Most frequent building movement

Answer 29

Settling

Question 30

Settling can be two different types

Answer 30

Uniform or differential

Question 31

Uniform settling

Answer 31

Parts of foundation settle at same rate and misalignment of structural members is minimal

Question 32

Differential settling

Answer 32

Different parts of foundation settle by different amounts. Causing significant misalignment of structural members.

Question 33

Differential settling can result from several factors.

Answer 33

Non uniforms soil conditions
Footings of different size
Footings at different elevations
Unequal load on footings

Question 34

Underpinning

Answer 34

Process of strengthening an existing foundation

Question 35

Underpinning is needed when there is

Answer 35

Excessive settlement because of inadequate foundation
Increase in load on foundation because of additions
Erosion of soil around foundation

Question 36

Shoring

Answer 36

Process of temporarily holding up building until underpinning can be accomplished. Done with timber, hydraulic pneumatic or screw jacks. Also holds up sheeting in trenches. Shores, cross braces and struts.

Question 37

Disruption in foundation integrity can cause

Answer 37

Compromise of building structural members