Types and classification

Question 1

Soil Categories types (how are they defined)

Answer 1

Reference to size, then if size too small plasticity

Question 2

Soil Categories types (how are they defined)

Answer 2

Reference to size, then if size too small plasticity

Question 3

Clay

Question 4

Clay

Question 5

Silt

Answer 5

0.05-0.002mm - small particles of disintegrated rock - little or no plasticity, little strength when dried. Exhibits dilatancy, if shaken water moves to surface, then when motion stops goes back in.

Question 6

Effect of organics on soils

Answer 6

detrimental effect on strength and compressibility properties of the material

Question 7

Indications from colour

Answer 7

descriptor, but can indicat chem, biol. or physical processes. Black-org matter, red/grey - Fe, in well drained Fe is rusty brown colour. In saturated soils O2 is depleted and Fe is reduced - blue/grey

Question 8

Particle shapes and sizes

Answer 8

angular, sub ang, sub roundd, rndd

More angular particles possess better engineering properties, i.e. higher shear strength.

Question 9

Soil structure (particle arrangement)

Answer 9

Loose (high voids), dense (close pack, minimal void).

Coarse and silts, mass great compared surface area, thus gravity has greater effect. Clays: high surface to mass ratio are more affected by electro forces than gravity

Question 10

Special Soil definition and categories

Answer 10

behaviour that is unusual and capable of causing problems. i.e. Collapsible soil

Question 11

Define Collapsible soil

Answer 11

Category of soil deposits experience high decrease in volume when exposed to water. (in arid regions)
-Can be solved by flooding and using mech processes prior to construction, prevent water from reaching

Question 12

Define Liquefaction

Answer 12

Occurs when saturated cohesionless sand deposits exist in loose condition. Vibration or shock waves cause grains to quickly move into a denser arrangement but pore water interferes and particle to particle contact is prevented.

• Cause temporary loss of shear strength (i.e. becomes viscous liquid)
• Drainage to remove saturation, or densification-compaction can solve this issue.

Question 13

Index properties

Answer 13

indicate type and condition of the soil, provide relationship to structural properties: -strength/compressibility, -tendency for swelling/permeability.
Coarse: particle properties, compaction are most signif (others: size, size distrib, part. shape, presence of fines, density)
Fine:consistency (firm/soft), plasticity are important. (others: water content, presence/type of clays)

Question 14

Particle size distrib test

Answer 14

Sieving: weight on each sieve converted to percentage of total sample. On semi-log paper.
Results:
-Well-graded: smooth slope accross, all sizes present
-Uniform: narrow vertical slope (little size variability)
-Gap-graded (absense of size, horizontal line in slope)

Sedimentation test (hydrometer) for silts and clays. Use hydrometer to measure density over time (deposition occurs, fines in suspension longer)
Well graded is poorly sorted.

Question 15

Clay

Answer 15

-

Question 16

Silt

Answer 16

0.05-0.002mm - small particles of disintegrated rock - little or no plasticity, little strength when dried. Exhibits dilatancy, if shaken water moves to surface, then when motion stops goes back in.

Question 17

Effect of organics on soils

Answer 17

detrimental effect on strength and compressibility properties of the material

Question 18

Indications from colour

Answer 18

descriptor, but can indicat chem, biol. or physical processes. Black-org matter, red/grey - Fe, in well drained Fe is rusty brown colour. In saturated soils O2 is depleted and Fe is reduced - blue/grey

Question 19

Particle shapes and sizes

Answer 19

angular, sub ang, sub roundd, rndd

More angular particles possess better engineering properties, i.e. higher shear strength.

Question 20

Soil structure (particle arrangement)

Answer 20

Loose (high voids), dense (close pack, minimal void).

Coarse and silts, mass great compared surface area, thus gravity has greater effect. Clays: high surface to mass ratio are more affected by electro forces than gravity

Question 21

Special Soil definition and categories

Answer 21

behaviour that is unusual and capable of causing problems. i.e. Collapsible soil

Question 22

Define Collapsible soil

Answer 22

Category of soil deposits experience high decrease in volume when exposed to water. (in arid regions)
-Can be solved by flooding and using mech processes prior to construction, prevent water from reaching

Question 23

Define Liquefaction

Answer 23

Occurs when saturated cohesionless sand deposits exist in loose condition. Vibration or shock waves cause grains to quickly move into a denser arrangement but pore water interferes and particle to particle contact is prevented.

• Cause temporary loss of shear strength (i.e. becomes viscous liquid)
• Drainage to remove saturation, or densification-compaction can solve this issue.

Question 24

Index properties

Answer 24

indicate type and condition of the soil, provide relationship to structural properties: -strength/compressibility, -tendency for swelling/permeability.
Coarse: particle properties, compaction are most signif (others: size, size distrib, part. shape, presence of fines, density)
Fine:consistency (firm/soft), plasticity are important. (others: water content, presence/type of clays)

Question 25

Classification tests

Answer 25

Particle size distribution (sieving)

Question 26

Particle size distrib test

Answer 26

Sieving: weight on each sieve converted to percentage of total sample. On semi-log paper.
Results:
-Well-graded: smooth slope accross, all sizes present
-Uniform: narrow vertical slope (little size variability)
-Gap-graded (absense of size, horizontal line in slope)

Well graded is poorly sorted.

Question 27

Sieving semilog calculations

Answer 27

D10: 10% passing size
D60/D10: uniformity quotient (Cu)
-wellgraded = Cu >10
-uniform = Cu

Question 28

Define clay characteristics

Answer 28

from alteration of rock minerals, crystalline sheet like minerals

• develop cohesion (between sheets and H2O; surface net negative charge, edges +/-, retains water longer due to charge (can remove by vaporising))
• develop plasticity
• mineral type not size that defines a clay (non clays of

Question 29

Clay structure

Answer 29

settling produces flocculated structure (edge to face arrangement of plates). Increased floculation in saltwater than freshwater.

• High void ration
• low density
• high water content
• Thixotropic : strength increases with age, especially after remolding.(engineering becomes safer over time)

Question 30

Generally define smectite

Answer 30

clays that swell or shink as changes in soil water occurs. (Montmorillonite, high net - charge, high capacity for ion exchange) Very high pressure forces from swelling!

Question 31

Define dispersive clays

Answer 31

Defloculate in still water and erode if exposed to low-velocity water (non-dispersives need high velocity to erode).

Question 32

Water content and consistency/plasticity of clays

Answer 32

high water content = liquid properties
lesser water = plastic properties
minimal water = semisolid then solid.

• liquid limit is water content division between liquid and plastic
• plastic limit is water content division between plastic and semisolid
• shrinkage limit (vol. does not decrease w/ decrease H2O) is water content division between semisolid and solid.

Question 33

Liquididity index.

Answer 33

Li = w% - PL%/LL%-PL% = w%-PL%/PI%
w= natural water content of soil