Soils

Question 1

Three Soil Classification Groups

Answer 1

1. Cohesive Soils
2. Granular Soils
3. Organic Soils

Question 2

Cohesive Soils

Answer 2

soil is compact, difficult to divide, and on desiccation, large cracks form (clay, silt)

Question 3

Granular Soils

Answer 3

soil with granular structure in rounded aggregates of from 1 to 10 mm (sand, gravel)

• surface is rough
• easily separated
• difficult to handle rich regions
• sound in humus rich regions

Question 4

Organic Soils

Answer 4

soil formed essentially of accumulated vegetation, not easily compacted

Question 5

Soil Consistency Terminology

Answer 5

• Cemented
• Firm
• Friable
• Hard
• Loose
• Plastic
• Sticky
• Soft

Question 6

Cemented

Answer 6

is not affected by moisture and is very hard

Question 7

Firm

Answer 7

succumbs to moisture

Question 8

Friable

Answer 8

crumbly soil that is capable of being reduced to small fragments of even small grains, when tilled friable soil will easily divide into small fragments (usually a loam)

Question 9

Soil Texture

Answer 9

classified by USDA as sand, loamy sand, sandy loam, loam, silt, sandy, clay loam, clay loam, silty clay loam, sandy clay and clay

Question 10

Aerobic

Answer 10

availability of free oxygen for organisms

Question 11

Anaerobic

Answer 11

no available free oxygen, often occurs in wetlands because of the continual presence of water

Question 12

Alluvial

Answer 12

soil formed by deposition on shores of lakes or large rivers, or in floodplains, alluvial soil is not homogenous, proportion of large grains depends on the speed and turbulence of the waters that deposited them, the obstacles encountered and the distance from the region of origin.

Question 13

Angle of Repose

Answer 13

(Angle of friction), an engineering property of granular materials. It is the maximum angle of a stable slope determined by friction, cohesion and the shapes of the particles. The angle of repose is the angle a pile forms with the ground.

Question 14

pH

Answer 14

an expression of the relative concentrations of hydrogen ions and hydroxyl ions in a soil sample. A scale range from 0-14. Terms acid and alkaline used.

Question 15

Acid

Answer 15

pH less than 7. Most common in areas with high rainfall and are often high in organic matter.

Question 16

Alkaline

Answer 16

pH greater than 7. Most common in areas with low rainfall.

Question 17

Neutral

Answer 17

pH equal to 7. Most plants prefer pH from 6.5 to 7.2.

Question 18

Plasticity

Answer 18

the ability of a soil to become deformed without breaking apart.

Question 19

Elasticity

Answer 19

the ability of a soil to return to its original shape after being subjected to a load condition.

Question 20

Liquid Limit

Answer 20

the minimum moisture content at which a soil will flow under its own weight.

Question 21

Permeability

Answer 21

the ability of a soil to transfer water.

Question 22

Proctor Compaction Test

Answer 22

test to determine the maximum practically-achievable density of soils and aggregates, and are frequently used in geotechnical engineering.

Question 23

Hydric Soil

Answer 23

soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part.

Question 24

Bearing Capacity

Answer 24

the load a material can withstand before failure.

Question 25

Compressive Strength

Answer 25

the maximum load a material can sustain before crushing or buckling.

Question 26

Shear Strength

Answer 26

resistance to the pressure of a downhill force.