Basic Principles of foundation design

Question 1

What causes differential settlement in shallow foundations?

Answer 1

Changes to load or soil properties leading to a state of failure

Question 2

What is an example of differential settlement that has not collapsed?

Answer 2

The Leaning Tower of Pisa in Italy

Question 3

What are the two types of settlement?

Answer 3

Uniform and differential settlement

Question 4

What causes structural failure due to settlement?

Answer 4

Heaving and expansive soils

Question 5

What leads to the expansion of soil and potential structural cracks?

Answer 5

Changes in the water table

Question 6

What is soil liquefaction and its conditions?

Answer 6

Ground acting like thick soup during strong earthquakes, affecting granular materials up to 1.5 m below the surface

Question 7

How do structural elements interact with soil?

Answer 7

They transfer loads to the ground and can vary in material and cross-sectional areas

Question 8

What are the types of loads affecting foundations?

Answer 8

Environmental actions, live loading, and dead load

Question 9

What are the key design properties of soil?

Answer 9

Hydraulic conductivity, stiffness, and strength

Question 10

How are applied loads characterized?

Answer 10

By magnitude, geometrical features, and type (static or dynamic)

Question 11

What is the limit state in foundation design?

Answer 11

A condition of excessive settlement or collapse to be avoided

Question 12

Differentiate between Serviceability Limit State (SLS) and Ultimate Limit State (ULS).

Answer 12

SLS is when a structure can’t support loads without moving excessively, while ULS is a complete collapse

Question 13

Describe the process of creating a bored pile foundation.

Answer 13

Soil is excavated to the desired depth, reinforcement installed, and the hole filled with concrete

Question 14

What is a piled raft foundation?

Answer 14

A combination of shallow foundation and piles to support loads

Question 15

How can the strength of soils be measured in the laboratory?

Answer 15

Using a shear box

Question 16

What assumptions are made regarding soil behavior under load?

Answer 16

Soil is semi-infinite, homogeneous, isotropic, and behaves in a linearly elastic manner

Question 17

What is the principle of superposition in assessing settlements?

Answer 17

It allows for the assessment of settlements at various locations based on the cumulative effect of multiple loads

Question 18

What laboratory test can estimate the angle of shearing resistance?

Answer 18

A simple test using a beaker, some sand, and a protractor

Question 19

How does the degree of saturation affect soil properties?

Answer 19

It influences the soil’s strength, stiffness, and hydraulic conductivity

Question 20

What is uniform settlement?

Answer 20

Sinking in soil and no cracks

Question 21

When do cracks form in differential settlement?

Answer 21

Cracks at an angle - max shear at 45˚

Question 22

What are other types of failure?

Answer 22

• Structural failure
• External factors

Question 23

When does failure occur?

Answer 23

Increasing load on the deep or shallow foundation or by increasing the height or steepening the angle of a slope

Question 24

What types of material does liquefaction take place in and what happens?

Answer 24

• Only in granular materials
• Pore water pressure pulls the grains

Question 25

What are shallow foundations also known as?

Answer 25

Footing

Question 26

What are foundations?

Answer 26

Interfacing element that (properly) spreads the structural load to the ground

Question 27

What are the characteristics of applied loads?

Answer 27

- Magnitude - Geometrical features - Type: - Static or dynamic - Boundary conditions, e.g., 1D

Question 28

What is limit state design?

Answer 28

Analysis of soil-structure interaction scenarios that lead to excessive foundation settlement or collapse of the soil/structure

Question 29

When are deep foundations used?

Answer 29

- Soil layer 2

Question 30

How is force distributed in deep foundations?

Answer 30

In a narrow column, part of the resistance will go to the base but most of force taken by friction with sides

Question 31

What are examples of deep foundations?

Answer 31

Bored pile or drilled shaft

Question 32

What is a pile foundation?

Answer 32

A pile foundation is a **long slender stiff structural** member which is used to **transfer loads from some surface structure through more or less soft soils to a certain depth in the ground**

Question 33

What happens when you transfer loads into a material?

Answer 33

increase effective stress

Question 34

What are fabric changes in soil usually accounted for?

Answer 34

soil density and/or water content

Question 35

What is a shear box?

Answer 35

Used to force a failure surface to form within a soil sample contained within a split box

Question 36

How is shear stress calculated?

Answer 36

𝜏=Q/A

Question 37

What does soil deformation lead to?

Answer 37

compression and consolidation

Question 38

When are spacers used?

Answer 38

Spacers used to make sure deep foundation-centred

Question 39

When are shallow foundations used?

Answer 39

- Soil layer 1 - Won't be more 5m - Where the soil has adequate strength

Question 40

How can collapse be avoided in terms of resistance?

Answer 40

Resistance bigger than loads

Question 41

What will you get at working load?

Answer 41

At working load, you will get actual settlement

Question 42

What value is the factor of safety between?

Answer 42

Between 2 and 4

Question 43

What is the significance of bearing resistance in foundation design?

Answer 43

It controls building collapse by determining the maximum force that can be applied without causing infinite deformation