Soils Deep Dive

Question 1

Slope: 1.5% - 2%

Answer 1

Parking Lot

Question 2

Slope: 2%

Answer 2

Ideal pitch away from building

Question 3

Slope: 3% Max.

Answer 3

Recreation areas

Question 4

Slope: 8% (1:12)

Answer 4

Ramp max. slope

Question 5

Slope: 10% maximum, 4% preffered

Answer 5

Building Site

Question 6

Slope: <25%

Answer 6

Site can be planted with grass

Question 6

Slope: 10%

Answer 6

Maximum slope for streets

Question 7

Slope: 25% - 50%

Answer 7

Site must be terraced, can’t be mowed

Question 8

Valley UP

Answer 8

The contours point up the slope, toward higher elevations.

Question 9

Ridge DOWN

Answer 9

The contours point down the slope toward lower elevations.

Question 10

How many types of soil are in the Unified Soil Classification System?

Answer 10

12

Question 11

(C) Clay size?

Answer 11

<.002 mm particle size which is not visible. Clay is floury when dry and sticky when wet. Clay swells with water and shrinks when dry.

Question 12

(M) Silt size?

Answer 12

.002 mm particle size, which is not visible. Occasionally plastic behavior.

Question 13

What are the two types of Silt?

Answer 13

ML, OL

Question 14

(S) Sand size?

Answer 14

.05-2mm particle size, which is just visible.

Question 15

What are the four types of Sand?

Answer 15

SW, SP, SM, SC

Question 16

(G) Gravel size?

Answer 16

2mm particle size.

Question 17

What are the types of Gravel?

Answer 17

-GW: Well Graded Gravel
-GP: Poor Graded Gravel
-GM: Silty Gravel
-GC: Clayey Gravel

Question 18

(O)

Answer 18

Organic Material

Question 19

(PT) Peat

Answer 19

Highly organic material

Question 20

(H) Elasticity

Answer 20

Designates an elastic soil

Question 21

What are the best soils for sub-grade material?

Answer 21

Gravels, the larger the particle size, the stronger the soil.

Question 22

What gravel is preferred for construction?

Answer 22

GW (Well Graded Gravel), GP (Poor Graded Gravel), GM (Silty Gravel)

Question 23

What soils have the highest bearing capacities?

Answer 23

Bedrock, Shale, & Slate

Question 24

What performance characteristics differ between soils?

Answer 24

Shear strength, cohesion, compressibility, permeability, and plasticity.

Question 25

Soils with clay content of 15% or more offer protection from _________, a risk in earthquake zones.

Answer 25

Liquefaction

Question 26

When is soil the most susceptible to liquefaction?

Answer 26

The more granular or loose the soil is.

Question 27

What is Bedrock?

Answer 27

Highest bearing capacity of all soil types, because it is SOLID ROCK.

Question 28

What is Shale & Slate?

Answer 28

Second highest bearing capacity. Soft rocks with a fine texture.

Question 29

What is Hard Pan?

Answer 29

Unbroken mixture of clay, sand, and gravel.

Question 30

What is a Standard Penetration Test?

Answer 30

This is a soil boring that takes a measure of the density of granular soils and the consistency of clays within the sample.

Question 31

How are Standard Penetration Tests measured?

Answer 31

The number of blows required to move the boring a certain distance.

Question 32

What is Auger Borings?

Answer 32

Used only for sand or clay, uses a standard auger bit.

Question 33

What is Wash Borings?

Answer 33

A water jet forces material into a 2-4 inch diameter pipe. This results in a heavily mixed boring.

Question 34

What is Karst Landscape?

Answer 34

An area comprised of soluble rocks, limestone, dolomite, or gypsum. The soil dissolves to form caves and peaks, and can cause sinkholes.

Question 35

What is Drainage Treatment?

Answer 35

Used to increase the strength of soil.

Question 36

What is Fill Treatment?

Answer 36

Undesirable existing soil is removed from the site, and new fill (soil) is brought in, then compacted.

Question 37

During compaction in Fill Treatment, what does it require?

Answer 37

Moisture to lubricate the soil particles.

Question 38

What is the Proctor Test in Fill Treatment?

Answer 38

Determines the optimal moisture content at which a given soil type achieves its maximum dry density.

Question 39

How are Fills placed?

Answer 39

In lifts of 8-12", each lift is compacted before the next one is placed.

Question 40

What is a Sheepsfoot Roller?

Answer 40

A machine used to compact fill.

Question 41

What is Densification of Soil?

Answer 41

Achieved through on-site compaction, vibration, heavy weights, and piles frilled with sand.

Question 42

What is Surcharging?

Answer 42

Pre-loading of the ground with fill to compact and settle the underlying soil before starting construction. The added fill is the removed, leaving only the compacted original soil. Expensive!

Question 43

What is Mixing?

Answer 43

Instead of complete replacement of soil with fill, a layer of sand or gravel is mixed into the existing soil.

Question 44

What is Expansive Soil?

Answer 44

Clays (aka Bentonite) expand when wet and shrink when dry. Because of this, foundations must be isolated from clay soil.

Question 45

What is the Angle of Repose?

Answer 45

The natural angle a pile of dirt or other material takes when at rest. The angle depends on grain size and moisture contents of the soils.

Question 46

What is the max. practical angle for changing grades without using retaining walls or other stabilization methods?

Answer 46

Angle of Repose

Question 47

What is a Silt Fence?

Answer 47

Used during construction to catch eroded sediment on site before it enters the storm sewer.

Question 48

How are Silt Fences places?

Answer 48

Parallel to contours

Question 49

What are the four erosion types?

Answer 49

-Sheet Erosion -Gully Erosion -Splash Erosion -Rill Erosion

Question 50

What is Sheet Erosion?

Answer 50

Uniform overland flow, can be difficult to notice.

Question 51

What is Gully Erosion?

Answer 51

Removal of soil along drainage lines by surface water runoff. Deep, wide, and unstable channels are formed.

Question 52

What is Splash Erosion?

Answer 52

First stage in the erosion process that occurs when raindrops hit bare soil.

Question 53

What is Rill Erosion?

Answer 53

Removal of soil by concentrated water running through small streamlets.