Soils

Question 1

Factors that determine soil strength

Answer 1

1. Water content
2. Depth of soil
3. Foundation type

Question 2

Soil permeability

Answer 2

“Well graded” means few air gaps and water cannot drain easily but is better for bearing. “Poorly-graded” means many air gaps and water can drain easily but may have higher compression. Mix of soils is best to diminish permeability because the small particles fill in the gaps of the larger particles.

Question 3

Hardpan

Answer 3

Mix of clay, gravel and sand. Good for bearing.

Question 4

Retention Pond

Answer 4

Retains water all the time. Has overflow drain at the top to either storm sewer or natural water source.

Question 5

Detention Pond

Answer 5

Detains water temporarily. Has overflow drain at the bottom to storm sewer.

Question 6

Catch basin

Answer 6

Temporarily detains water to delay release of water to storm sewer and catch debris. If clogged with debris, leads to street flooding.

Question 7

5 stormwater management systems

Answer 7

1. Retention pond
2. Detention pond
3. Catch basin
4. Cistern
5. Bioswale

Question 8

Cistern

Answer 8

Collects rainwater for reuse

Question 9

Bioswale

Answer 9

Directs and filters water to underground aquifer through use of native plants.

Question 10

Liquefaction

Answer 10

Soil liquefaction, also called earthquake liquefaction, is ground failure or loss of strength that causes otherwise solid soil to behave temporarily as a viscous liquid. The greater the soil density, the lower the liquefaction risk. Clay content of 15% or more is good protection. Usuallly found with fine to medium grained sands/silts in loosely packed layers but also found in quick clays.

Question 11

The Unified Soil Classification System

Answer 11

5 broad categories, 15 classifications based on particle-size characteristics, liquid limit, and plasticity index.

Question 12

Hydrology considerations

Answer 12

• Presence and drainage
• Identify wetlands, flood plains, riparian zones, springs and seeps
• Consider off-site hydrology/run-off
• Protection of watershed
• Sensitivity to development (erosion, sedimentation)
• Total max daily loads of stormwater

Question 13

Expansive soil

Answer 13

Clay soils vulnerable to expansion and contraction that can cause pavement and foundation cracking. Must use deep foundations with this type of soil. Ex. bentonite clay.

Question 14

Land Development Regulations

Answer 14

Local street design, open space, lighting, subdivision standards, minimum landscaping. Can be waived by local officials unlike zoning which requires variance hearing.

Question 15

Assessing “fit” for a site

Answer 15

• zoning
• local development plan
• physical features
• neighborhood
• region
• community
• accessibility

Question 16

Ecological Services Analysis

Answer 16

Understand and measure landscape characteristics in terms of environmental quality and economic value.

Question 17

Environmental Services Assessment

Answer 17

Buyers, development and lenders require risk assessment to avoid/limit liability for environmental contamination.

Question 18

Environmental Transaction Screen

Answer 18

Performed by a person generally knowledgable about land and real estate. Adequate for average home buyer. Best for undeveloped site.

Question 19

Phase I ESA

Answer 19

• Performed by a professional
• Must follow ASTM E-1527
• Cost-effective analysis based on observation and snythesis of existing studies and maps (no collection or testing of samples
• Standard by which to minimize risk and also evaluate final design product

Question 20

Brownfield

Answer 20

A former industrial or commercial site where future use is affected by real or perceived environmental contamination. We can no longer assume that a site is healthy.

Question 21

3 Types of Pavers

Answer 21

Type I: high traffic areas such as driveways or entrances
Type II: walkways and areas of moderate traffic
Type III: low traffic areas like patios

Question 22

3 Grades of Brick for pavers

Answer 22

SX: Resistant to frost/freeze and thaw. Used for pavers. High installation cost.
MX: Only used for paving in dry or well-drained areas.
NX: Not suitable for paving

Question 23

Soil bulk density

Answer 23

Weight per volume of any unti of soil. The higher the bulk density, the greater support it can provide for a foundation.

Question 24

Liquid Limit

Answer 24

The moisture content at which a soil tends to flow and will not retain its shape.
Atterberg limits test: Cup is filled with soil, V-shaped groove is dug, and cup is dropped until soil gap is closed.

Question 25

Plastic Limit

Answer 25

The moisture content at which a soil deforms plastically. Atterberg limits test: Soil is rolled into long threads and point at which it crumbles is measured.

Question 26

Plasticity Index

Answer 26

(PI) The numerical difference between the PL and LL. A PI over 15 is a good indicator of expansive soils.

Question 27

Grading standards

Answer 27

Included in local ordinances. Grades established with concerns for safety, comfort, drainage, access, ice, etc. Provides a minimum, preferred and maximum grade (%). Lawns: 2-8% Athletic fields: 1% Mowed slopes: 10% Planted slopes: 5% Longitudinal slope of parking lots: 2-3% Longitudinal slope of roads: 10% max (also consider climate)

Question 28

Most common environmental impact of disturbed sites

Answer 28

The temporary influence of storm water runoff in the forms of erosion, sedimentation, loss of soil and degradation of downstream water. When brush is removed, the soils are more prone to erosion. You must think about short term effects in addition to long term design.

Question 29

Ways to minimize disturbed site area

Answer 29

1. Make roads parallel to contours 2. Cluster built areas 3. Leave vegetative strips between disturbed ares

Question 30

Angle of repose

Answer 30

The steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°. The morphology of the material affects the angle of repose; smooth, rounded sand grains cannot be piled as steeply as can rough, interlocking sands. Gravel: 45 Dry clay: 40 Dry sand: 35

Question 31

Methods of soil stabilization

Answer 31

1. Retaining walls: interlocking block, cantilevered concrete 2. 3D geosynthetic materials 3. Buttresses and caissons

Question 32

5 categories of USCS

Answer 32

1. Gravels: course, unconsolidate, large grain, best for foundations 2. Sands: finer than gravel, when compacted can be a good foundation, but susceptible to movement when saturated. More course sand is better for a foundation because course soil is better than fine soil. 3. Silts & Clays (Liquid Limit below 50%): Silts are finer than sand, inorganic, found in at the bottom of water. Not good for foundations. 4. Silts & Clays (Liquid Limit above 50%): Clay is even finer, very cohesive and plastic. Can sometimes be used to bear weight, but not preferable, rated more poorly than all the above. 5. Organic Soils: Not good for anything. Can not be used to support a foundation.

Question 33

Coarse-grained vs fine-grained soils

Answer 33

Coarse: 50% or more of material is larger than no. 200 sieve. Fine: 50% of more pass through the no. 200 sieve

Question 34

Bentonite clay

Answer 34

Assembly of clay inside kraft paper packages or plastic liners in panel form. Bentonite expands with moisture and prevents water from getting past. Often combined with geotextiles and can be used on both blind side and positive side waterproofing.

Question 35

Waterproofing, 3 locations and 4 types

Answer 35

Control of moisture and water that is subject to hydrostatic pressure. Positive side (outside of foundation wall) Negative side (inside of foundation wall) Blind side (applied before the wall is in place against the shoring) 1. Sheet membranes (positive side) 2. Fluid applied systems (positive side) 3. Cementitious systems (positive side + neg for backup) 4. Bentonite systems (positive or blind side)

Question 36

Dampproofing, location and 5 types

Answer 36

Control of moisture and water that is NOT subject to hydrostatic pressure (not below water table). Always install on positive side. 1. Admixtures: salts or powdered iron added to concrete mixture reduce strength but make less permeable). 2. Bituminous coatings: Asphalt or coal tar pitch. Cannot seal cracks that develop. 3. Cementitious coatings: Portland cement mortar troweled over rough surface to provide smooth surface as base for other dampproofing or used on its own. 4. Membranes: Built-up layers of hot or cold-applied asphalt felts. High cost and difficult to install so usually used for waterproofing. 5. Plastics: Silicone and polyurethane coatings. Usually used above grade.