Chapter 5 -Intro to foundation

Question 1

What do foundation engineers need to consider?

Answer 1

1) The size of a building
2) Load to be carried
3) Conditions on the site
4) The climate
5) Presence of water & winds
6) Potential earthquake

Question 2

What is the simplest and most common foundation type?

Answer 2

Shallow foundation

Question 3

What are the advantages of ground modification (Soil stabilization)), and what type of footing is used?

Answer 3

Spread footing is used. It may reduce foundation settlement, groundwater flow and increase the bearing pressure on a soil surface

Question 4

True or false: Most old houses (1930s or before) don’t have a reinforced foundation which is against the code, therefore they must be monitored and may get demolished.

Answer 4

False. no need to monitor or demolish. The only thing to do is a foundation replacement

Question 5

How a column supports a structure?

Answer 5

A column is driven into the soil to support a structure by transferring building loads to a deeper and stronger layer of soil/rock.

Question 6

True or false: Shallow foundation is the best fit for skyscrapers

Answer 6

False. It is not a good fit due to the skyscrapers heavyweight

Question 7

When do we use piles?

Answer 7

Piling technic is used when we need to strength the current condition of the soil so it would be able to accumulate more weight.
In short: (weak soil/heavy weight)

Question 8

What is the height limit for timber piles?

Answer 8

30m (length)

Question 9

What is cohesionless soil? How does it fail?

Answer 9

Grains do not stick together; shear strength is due to the friction between the soil grains. Failure looks like a steeper angle

Question 10

What is Cohesive soil? How does it fail?

Answer 10

There’s no friction between the soil grains and the shear strength. Failure looks like 2 little rumps.

Question 11

What is a safe excavation height for soft and medium clay?

Answer 11

Safe Vertical excavation on cohesive soil (clay) can range from 1.5m for soft clay to 5.5m for a medium clay.

Question 12

True or false: Excavations needs to be supported all the time during construction

Answer 12

False. Apart from rock that can be unsupported, any other type of soil can only be temporarily unsupported

Question 13

How does the bottom of cohesive soil excavation react?

Answer 13

During cohesive soil excavation, heaving (rising) of the bottom of the cut will occur due to the weight of the soil on the sides of the cut

Question 14

What is Liquefaction (quicksand)? In what type of soil excavation it occurs? What is boiling or piping?

Answer 14

It’s when the water pressure is equal to the soil weight in cohesionless soil excavation.
Boiling - This happens when water pressure is strong enough to move subsurface soil up through the bottom of the cut.

Question 15

What are the 3 ways to prevent Embankment Failure? (When water pressure affects the excavation)

Answer 15

1) Stabilizing side slopes by providing lateral support by cutting them back to an angle equal to or less than the angle of repose

2) Dewatering the soil surrounding the excavation which will increase the stability of the sides and bottom

3) Driving piles or inserting stone columns into soil across the potential slip plane, it will increase the shear resistance

Question 16

True or false. Construction fatalities are more common in underground work (excavation) compare to the above groundwork

Answer 16

True.

Question 17

What is shoring? Cofferdam? Give examples of shoring types

Answer 17

Shoring: Lateral support for the sides of the excavation.
Cofferdam: a shoring system that completely encloses an excavation

1) Sheet pilling
2) Timber shoring
3) Aluminum hydraulic shoring
4) Lagging

Question 18

What is bentonite?

Answer 18

It is a type of clay produced from volcanic ashes and is also used for slurry walls

Question 19

When do we use slurry?

Answer 19

A slurry (such as clay and water) is used to fill the excavation as the soil is removed