Consolidation

Question 1

What is the angle of repose for dry sand and what creates the shear strength

Answer 1

Approx 30°. The friction between particles cause shear strength

Question 2

Sandy soil compressibility properties

Answer 2

Low compressibility
Therefore low excess pore-water pressure
High permeability
Therefore water dissipates very fast

Question 3

Clayey soil compressibility properties

Answer 3

High compressibility
Therefore high excess pore-water pressure
Low permeability
Therefore water dissipates very slow

Question 4

Settlement phases diagram

Answer 4

1) soil and water give a known height
2) separated out there’s a layer of voids and a layer of solids
3) compression changes height/volume of voids, solids volume:height stays the same

Question 5

What is immediate settlement

Answer 5

The initial settlement the soil experiences

Question 6

What is consolidation settlement

Answer 6

Settlement due to the expulsion of water

Question 7

What is secondary compression

Answer 7

The compression of soil particles
E.g happens in organic soils

Question 8

Compression time for sand compared to compression time for clay

Answer 8

Compression in sand is almost instantaneous.
Compression in clay takes time to reach a steady state.

Question 9

What is time noted as in a compression graph

Answer 9

Either t^0.5 or logt

Question 10

What is the over consolidation ratio (OCR)

Answer 10

Soil is “normally consolidated” when the pre consolidation pressure equals the currently existing effective vertical overburden pressure. If the pre consolidation pressure is greater than the existing overburden pressure, the soils is “over consolidated”. And if the pre consolidation pressure is smaller than the existing overburden pressure the soil is “underconsolidated”. Therefore for normal consolidation: OCR=1