Lecture 11

Question 1

What is the equation for relative compaction?

Answer 1

RC=⍴_d/⍴_dmax

Question 2

What is compaction?

Answer 2

Process of increasing the dry density of soil by reducing the volume of air

Question 3

When do you compact soil?

Answer 3

Partially saturated soil

Question 4

When does consolidation occur in soil?

Answer 4

When it is saturated

Question 5

How can volume be reduced by consolidation?

Answer 5

Removal of water

Question 6

How can volume be reduced by compaction?

Answer 6

Removal of air

Question 7

How can soil densification happen by compaction?

Answer 7

Through the application of external loads and mechanical mixing.

Question 8

How can soil densification happen by consolidation?

Answer 8

Through the application of external loads.

Question 9

Why do we compact soil?

Answer 9

To improve soil properties

Question 10

What properties will be increased or reduced during compaction?

Answer 10

• Increase stiffness (reduce settlement)
• Increase strength
• Reduce permeability

Question 11

When would compaction be useful?

Answer 11

For road embankments nd retaining walls so no settlement occurs

Question 12

What are some compaction methods?

Answer 12

• Static load/pressure
• Kneading
• Impact
• Vibration

Question 13

How does static load/pressure work?

Answer 13

Put something heavy on material, use black rollers

Question 14

How does kneading work?

Answer 14

Circular movements that cycle through the grains and move them around to find more stable position, steel rollers, and rubber wheels

Question 15

How does impact work?

Answer 15

More violent dynamic using a load

Question 16

What method can be used for fine-grained materials?

Answer 16

• Kneading and impact

Question 17

What methods can be used for coarse-grained material?

Answer 17

• Vibration and static load/pressure

Question 18

What is the lift thickness?

Answer 18

Thickness of the layer you can put on soil

Question 19

What are the 3 methods for quality control?

Answer 19

1. Sand Cone Test
2. Ballon Test
3. Nuclear density test

Question 20

How can you check the soil quality?

Answer 20

Regularly measure the density of the material

Question 21

What are the steps for the sand cone test?

Answer 21

1. Calibrate material
2. Pick a good testing spot and representative
3. Prep testing location
4. Dig hole and keep moisture and collect soil
5. Place and open the sand cone
6. Close the valve and measure the final weight
7. Calculate bulk and dry soil

Question 22

What are the steps for the ballon test?

Answer 22

1. Choose a test spot
2. Prep test location
3. Adjust the ballon pump
4. Dig a hole and collect soil
5. Adjust the balloon pump and take the volume
6. Calculate bulk and dry soil

Question 23

Before you go to the field what must you do?

Answer 23

• Do lab tests
• Look at British standard and ASTM

Question 24

How can compaction be analysed?

Answer 24

From a dry density and water content graph

Question 25

What is the saturation line?

Answer 25

The theoretical line says there is no more void space so can't be compacted anymore

Question 26

What does it suggest when soil is at the beginning of the P_d and W graph?

Answer 26

- Too little water then glue between them - voids mostly air - Meniscus water

Question 27

What happens when there is excess water in the soil?

Answer 27

Excess water displaces soil particles

Question 28

What does increased water do to the soil?

Answer 28

- Makes the soil more workable

Question 29

How can compaction be tested using the Proctor Method?

Answer 29

- Start from a low water content 2-3% - Minimum of 5 samples - Load samples in layers and compact with ahammer - Calculate P_d - Plot compaction curve - Establish w_opt and P_dmax

Question 30

How can the P_d be calculated from the Proctor Method?

Answer 30

- Know the volume of the layer - Extract the material that's inside and measure the mass - Can find bulk density and dry density

Question 31

How does soil type affect the curve on the density and water content diagram?

Answer 31

Maximum dry density decreases whereas the optimum water content increases with decreasing particle sizes and increasing plasticity

Question 32

How does compaction effort affect the curve?

Answer 32

For a given soil, the maximum dry density increases whereas the optimum water content decreases with increasing compaction effort