Earthworks and Grading Flashcards
Classifies soil into 7 groups based on particle size distribution, liquid limit and plasticity index (engineering properties and suitability for highways)
AASHTO Soil Classification System
2 major groups of soil based on AASHTO
Granular Materials
Silt-Clay Materials
Pass less than 35% of materials through a No. 200 sieve
Granular Materials
Pass more than 35% of the material through a No. 200 sieve
Silt-Clay Materials
Particle sizes according to AASHTO
Boulder - above 75mm
Grave - 75mm to No. 10 sieve
Course Sand - No. 10 sieve to No. 40 sieve
Fine Sand - No. 40 sieve to No. 200 sieve
Silt-Clay Particles - passing No. 200 sieve
Divides soils into three basic categories; was devised mainly for highway engineering purposes
Unified Soil Classification System (USCS)
Three basic soil categories according to USCS (highway engineering)
Coarse-grained Soils
Fine-grained Soils
Organic Soils
Pass less than 50% fines through a No. 200 sieve
Coarse-grained Soils
Pass more than 50% fines through a No. 200 sieve
Fine-grained Soils
Type of soil identified by visual examination
Organic Soil
Soil classification by origin
Residual Soils
Transported Soils
Soil that is formed in place through weathering of bedrock and disintegration of organic matter
Residual Soils
Materials that have been moved from another place by glaciation, wind, water, or gravity
Transported Soils
Property of soil; basically refers to amount of clay particles in a soil sample
Colloidal Content
Property of soil; refers to the upward movement of water above the water table as a function of fine soil texture
Capillarity
Property of soil; refers to the ability of soil to transmit water downward by force of gravity; function of a pore space and varies with void ratio, grain size and distribution, structure, degree of cementation, degree of saturation, and degree of compaction
Permeability
Measure permeability of soil
Percolation Test
Property of soil; refers to the ability of soil to return to its original state after being deformed by a load
Elasticity
Soil property; refers to the ability of soil to be deformed under pressure without cracking or crumbling, and to maintain a deformed shape after pressure is released; an important factor in road and foundation work and is more significant under increasingly greater loads
Plasticity
The moisture content at which a soil changes from the liquid state to the plastic state, measured when soil in a shallow dish flows to close a 12.5 mm groove after 25 drops from 1 cm
Liquid Limit
Test performed on soils passing the No. 40 sieve to establish the following
Atterberg Limits
The water content at which a silt or clay material will just begin to crumble when rolled into a tread approx. 3.2 mm (1/8 inch) in diameter
Plastic Limit
Defined as the Liquid Limit minus the Plastic Limit: LL - PL = ?; rang of water content over which sediment behaves
Plasticity Index (PI)
Refers to the ability of a soil sample to bind together when moderately dry; soils that are less of this are easy to excavate but, on vertical side slops, cannot be maintained without support (ex. beach sand)
Cohesion
The measured volume change of soil as a result of changed soil structure and the expulsion of water
Compressibility
Refers to the densification process through the compaction and expulsion of air
Compaction
The ability of a soil to bear a load without failure; depends on both upon internal friction between soil particles and upon cohesion
Bearing Strength
The extent to which soil mass can withstand the forces of wind or water erosion
Erodibility
The relative acidity or alkalinity of the soil; has an effect on nutrient availability
pH Level
Refers to the existence of moisture in soil that make water available to plants
Moisture Content
Three Types of Termite Proofing
Physical Barriers
Chemical Barriers
Bait System
Slow-acting insect-growth regulator that entire workers population and the entire termite colony
Hexaflumuron
The grade after all landscape development has been completed; the top surface of lawns, plantings beds, pavements, etc.; normally designated by contours and spot elevations on a grading plan
Finished grade
The top of the material on which the surface material, surface topsoil, and pavements (including base material) is placed; represented by the top of a fill situation and the bottom of a cut excavation
Subgrade
Refers to a subgrade that must attain a specified density
Compacted subgrade
Refers to a subgrade that indicates a soil that has not been excavated or changed in any way
Undisturbed subgrade
Imported material normally coarse or fine aggregate that is typically placed under pavement
Base or sub-base
Refers to the elevation of the first floor of a structure, but may be used to designate the elevation of any floor
Finished floor elevation
The process of removing soil; proposed contours extend across existing contours in the uphill direction
Cut or cutting
The process of adding soil; proposed contours extend across existing contours in the downhill direction
Fill or filling
The densification of soil under controlled conditions, particularly a specified moisture content
Compaction
Normally the top layer of a soil profile, which may range in thickness from less than an inch to over a foot; has high organic content, thus, it is subject to decomposition, and not an appropriate subgrade material for structures
Topsoil
Methods for calculating cut and fill (earth) volumes
Average end area
Contour area
Borrow pit (grid)
Three types of visual form of grading
Geomorphic
Architectonic
Naturalistic
This type of grading wherein the proposed blends ecologically and visually with the character of the existing natural landscape; repeats similar landforms and physiographic structure; the intent of this category is to minimize the amount of regrading to preserve the existing landscape character
Geomorphic
The proposed grading in this category creates uniform slopes and forms which usually are crispy defined geometric shapes; appropriate where the overall impact is man dominated or where a strong contrast is desired between the built and natural landscape
Architectonic
The most common type of grading particularly in suburban and rural settings; a stylized approach in which abstract (or organic) landforms are used to represent or imitate the natural landscape
Naturalistic
Vegetated or paved embankments, somewhat dike-like in appearance, commonly used by landscape architects for enclosure and separation purposed; may also provide protection from climatic elements
Berms
Preferred minimum and maximum number of risers for a set of stairs
3-12 risers
Handrails are normally required on stairs with _____ or more risers
5
Stair treads should pitch ____ in/ft in the downhill direction to insure proper drainage
1/8
Low curbs commonly used along the edges of stairs for safety and maintenance purposes
Cheek walls
Inclined sidewalk or driveways usually at a uniform slope
Ramp
Typical range of slopes for pedestrian use
5 to 8%
Handrails, particularly for handicapped use, are normally required on ramps of ___ % and greater slopes
5%
An intermediate landing is usually required where ramps exceed ____ in length
30ft (9m)
Ratio of slope to be visually significant
5:1
General ratio of planted slopes
2:1
Ratio of slope for mowed lawn areas
3: 1
4: 1 - preferred maximum
The extent of surface conditions on completion of grading
As graded
In-place solid rock
Bedrock
A relatively level step excavated into earth material on which fill is to be palced
Bench
Earth material acquired from an off-site location for use in grading on a site
Burrow
