Section 2 - Soils Analysis

Question 1

Porosity

Answer 1

Amount of pore space in soil; is related to grain size distribution + consolidation. Clay soils usu. have high porosity.

Question 2

Soil Permeability

Answer 2

rate at which water will freely drain through a soil. Clay usu. has low permeability and may settle considerably when loaded with a foundation

Question 3

Soil Strength

Answer 3

• a soil’s ability to resist deformation. Depends on cohesion and friction
• Cohesion –ability of grains to stick together (water)
• Friction –between grains and form density and weight of material above
• Sensitivity – refers to how easily a soil loses strength due to disturbance

Question 4

Shear Strength

Answer 4

Force and Strength of the soil and minerals holding the block in place. Fights the Shear force that pulls the block down. Tested using a 4-bladed vane driven into soil and turned until failure (torque nec. to force failure = shear strength measure of frictional resistance and cohesion of soil)

Question 5

Bulk Density

Answer 5

• Dry weight of undisturbed soil particles/ soil unit volume
• Includes both solids and pores and is expressed as grams/cc
• Desirable bulk densities vary depending upon soil texture
• Higher bulk density usu. = greater foundation support

Question 6

Atterberg Limits - Liquid + Plastic

Answer 6

Measures water in a soil at a pt. where soil begins to act as a liquid or begins plastic flow; LL-PL = PI (PLASTICITY INDEX)

• Liquid Limit (LL) - moisture content at which a soil tends to flow + won’t retain shape
• Plastic Limit (PL) - moisture content at which soil deforms plastically; soil rolled into long threads until they just begin to crumble at a dia. of 3 mm. If it contains more moisture than plastic limits

Question 7

(C) Clay

Answer 7

A clastic mineral particle of any composition that has a grain size smaller than 1/256 mm. The term is also used in reference to a broad category of hydrous silicate minerals in which the silica tetrahedrons are arranged into sheets.

• Unified Soil Classification System Symbol - C

Question 8

(M) Silt

Answer 8

granular material of a size somewhere between sand and clay derived from soil or rock

• Unified Soil Classification System Symbol - M

Question 9

(S) Sandy soil

Answer 9

large pore space which provides quick drainage

• Unified Soil Classification System Symbol - S

Question 10

(G) Gravel

Answer 10

• granular rock particles ranging in size from 0.25” to 3.25”.
• -any larger rock pieces are called “cobblestones”, largest: “boulders”.
• Unified Soil Classification System Symbol - G

Question 11

(O) Organic Soils/Histosols

Answer 11

form in continually saturated areas (marshes, bogs) where low 0 2 prevents microbial breakdown of plant materials

• Unified Soil Classification System Symbol - O

Question 12

(H) High Liquid Limit

Answer 12

• Water content > 50%, high plasticity (v. cohesive or sticky clay)
• Unified Soil Classification System Symbol -H

Question 13

(L) Low Liquid Limit

Answer 13

• Water content
• Low plasticity
• Unified Soil Classification System Symbol - L

Question 14

(W) Well-Graded Soils

Answer 14

Has a good representation of all particle sizes, in proportionate quantities, from the largest to the smallest. The smaller particles fill the voids between the larger particles. This proportioning generates stability through increased grain-to-grain contact.

• Unified Soil Classification System Symbol - W

Question 15

(P) Poorly Graded Soils

Answer 15

• Grain distribution affects consolidation and settlement

* Unified Soil Classification System Symbol - P

Question 16

GRADING STANDARDS: lawn

Answer 16

1% MIN, 10%MAX

2-8% preferred

Question 17

Grading Standards: athletic fields

Answer 17

1% min, 2%max

• 1% preferred

Question 18

Grading Standards: Mowed Slopes

Answer 18

5% min, 25%max

• 10% preferred

Question 19

Grading Standards: Unmowed Slopes

Answer 19

no min, Angle of repose (typ. 30-45 deg) max

• 25% preferred

Question 20

Grading Standards: Planted Slopes

Answer 20

1% min, 10%max

• 5% preferred

Question 21

Grading Stnd: Berms

Answer 21

5% min, 25%max

• 10% preferred

Question 22

pH

Answer 22

an expression of the relative concentrations of hydrogen ions in a soil sample. A scale range form 0-14 is used. The terms “acid,” “neutral,” and

“alkaline” are used when describing the soil pH or “soil reaction.”

Question 23

Acid

Answer 23

Used in referring to soils with a pH less than seven (7). These soils are most common in areas

with high rainfall and often are high in organic matter.

Question 24

ALKALINE

Answer 24

Used in referring to soils with a pH greater than seven (7). These soils are most common in

areas with low rainfall.

Question 25

Neutral

Answer 25

Used in referring to soils with a pH equal to seven (7). Most plants prefer a pH from 6.5 to 7.2 . However, some prefer acid soils with a pH from 5.0 to 6.5 and others survive quite well with a pH from 7.5 to 8.0.

Question 26

Soil Texture

Answer 26

Refers to the relative percentages of the primary soil particles , or separates, in a soil mass.

Question 27

Soil Structure

Answer 27

Refers to the arrangement of soil particles and how they are grouped together into aggregates.

Question 28

Soil Separates

Answer 28

The individual size groups of primary soil mineral particles of sand, silt, and clay.

Question 29

Sand

Answer 29

The largest mineral particle of the soil separates. It is characterized by large pore space allowing good aeration and rapid passage of water.

Question 30

Silt

Answer 30

The intermediate-sized mineral particle of the soil separates.

Question 31

Clay

Answer 31

The smallest mineral particle of the soil separates. It is characterized by slow drainage and poor aeration but has the best nutrient holding capacity of all the soil separates.

Question 32

Loam

Answer 32

Generally a fertile and easily manageable soil consisting principally of sand (±40%) and silt.(t40%) particles with some clay (120%).

Question 33

Salinity

Answer 33

Refers to excess salts in soils. This is common in arid areas with low rainfall because salts are not leached out of the soil as easily as they are in areas of high rainfall. High salts can be a result of the quality of irrigation water, fertilizers, chemical amendments, or manures high in salt content.