Soils and Aggregates Flashcards
What are the Soil properties that help determine the spatial allocation of land-uses, the design and construction of structures, and the selection and installation of plant materials
Physical and Chemical Properties
Aggregates
Crushed rock or gravel
What are the 3 characteristics that define a Soil Profile?
textures, mineral contents, and chemical makeup
What are the soil Horizons
O, A, B, C, D
O/A Horizon (Organic Horizon) (2”-2’)
Surface Layer
B Horizon (Subsoil) (4”-8’)
Horizons of Maximum Accumulation
Clay
C Horizon (Substratum) (Parent Material)
Weathered parent material
D Horizon (Underlying Stratum)
BedRock
Soil Particle Sizes
(1) Clay (2) Silt (3)Sand (4) Gravel (5)Cobbles
Residual Soils
Remains above its parent rock
Transported Soils
Materials that have been moved from another place by glaciation, wind, water, or gravity
What was the USDA Classification System developed for?
Agriculture
USDA Classification System
Describes the relative proportion of clay, silt, and sand particles
What are the 11 Basic Soil Orders of the USDA Classification System based on?
Climate, Parent Material, Vegetation
What was the AASHTO Classification System developed for?
Devised for highway construction suitability
Engineering Properties of Soils
What are the 2 major soil groups in the AASHTO Classification System?
Granular Materials & Silt-Clay Materials
What were the Unified Systems developed for?
Devised for highway engineering
What are the 3 soil categories in the Unified Systems?
Coarse-grained Soils, Fine-grained Soils, Organic Soils
Order Coarse-grained, Fine-grained, Organic Soils from Excellent to Not Suitable, for use as Foundation Material.
Coarse-Grained: Excellent to Fair
Fine-Grained: Fair to Poor
Organic Soil: Not Suitable
Cumulose Soil
Organic
What are the Physical Properties of Soil?
Texture, Color, Density, Capillarity, Permeability, Shrinkage and Swell, Cohesion
How to obtain information about soil texture?
Soil Survey Report
What is Soil Density?
The Total Volume of Solids and Voids in Soil
Capillarity
Upward movement of moisture or water above the water table as a function of fine-textured soil
What are Clay & Silts and Coarse-textured soils capillary action?
Clay & Silts have High Capillary action
Coarse-textured soils have a lower capillary action
Permeability
The ability of soil to transmit water downward due to gravity Pore space
Shrinkage and Swell
Buildup and release of capillary tensile stresses within soil due to water
Cohesion
The ability of a soil sample to bind together when moderately dry
Elasticity
The ability of soil to return to its original shape after being deformed by a load. Compatibility of a soil
Plasticity
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
Liquid Limit
The liquid limit refers to the moisture content at which soil passes from a liquid to a plastic state as moisture is removed
Plastic Limit
Plastic Limit refers to the moisture content at which soil passes from a plastic to a semisolid state as water is removed
Frost Susceptibility
The relative tendency of some soil to swell due to frost when the moisture in the soil freezes
Are Fine-Grained or Coarse-Grained soils more susceptible to frost-action?
Fine-grained are more susceptible to freeze than coarse-grained
Compressibility and Compaction
Compact soil to increase its ability to support the weight
Bearing Strength
The ability of a soil to support a load without failure
What 3 factors affect Bearing Strength?
Water Content, Rate and time of loading, Confining pressure
What are the 3 components of Drainage?
Runoff, Internal Drainage, Permeability or porosity
Erodibility
The extent to which a soil mass can withstand the forces of wind or water erosion
Spatial Variability
Most urban sites consist of more than one soil type but are seldom mapped
Available Moisture and Adequate Drainage
Ideal Ratio Airspace to Water 1:1
Soil pH
Acidity or alkalinity of a Soil
What are the soil pH levels for acidic soil? For alkaline soil?
Acid is 0-6.5
Neutral is 6.6 - 7.3
Alkaline is 7.4 - highest
Colloidal Content
Refers to the number of clay particles in a soil sample
Depth
Depth to Bedrock, to water table or to unweathered parent materials
At what depth should plants be installed?
Between 18” - 36”
Issues with Urban Soils
Compaction, Increased runoff, Oxygen deficient environment, severely inhibited root growth, Increased thermal conductivity, Limited nutrient availability
Natural Granular Materials
Sand, gravel, crushed stone
Manufactured Granular Materials
Slag, vermiculite, pumice, and crushed brick
Relevant Properties of Aggregates
Cleanliness, Soundness, Gradation
Common Applications of Aggregates
Foundations, Finished Surfaces, Vehicular Roads and Parking Areas
Soil is made up of
minerals, water,air
