Site Flashcards
Foundations
Transfer buildings structural loads to the ground
- reach bedrock or soil competent enough to bear weight, of building
- Get below frostline
Buoyant upload forces
When underground water pushes upon a building
- makes it want to “float”
Dead loads
Weight of the building, permanent
Live loads
People, furnishings, weather, temporary or moving
Lateral loads
Wind, seismic, soil and hydrostatic pressure (lateral soil loads)
Building settling
We want buildings to settle evenly
- IF a building is on rock, settling is negligible
- People start to feel the difference at I degree slope
Largest to smallest particles
Boulders
Cobbles
Gravel
sand
Silt
Clay
Organic soil
Peat and top soil
Must be cleared from the site and stored because the building can’t bear on it
Changes form with biological activity /(plants, rot, etc. )
Can re-use later for landscaping
Arrange from least to most competent particles for supporting a building
Gravel
Sand
Silt
Clay
Which particle is weird and changes behavior most?
Clay - plate like particles, high liquid amount, can be highly expansive, can consolidate (remove moisture under pressure) , brittle, sticky
Which are frictional?
Gravel, sand- rely on internal friction for strength
Which are cohesive?
Clay and silt (less than clay)
What is the liquid limit of a soil?
The water content at which the soil transitions from semi-solid to fluid.
Sand and silt change a lot with water content - IF there is too much water in the ground or an earthquake happens, the ground can liquify
What is plastic limit?
How much water a soil can absorb before starting to expand
It we keep adding water, once it flows it has reached its liquid limit
What is shear strength (as it applies to earth materials)?
The resistance of particles sliding over each other due to friction or interlocking, and possibly cementation or bonding at particle contact
Densely packed course grain soils exhibit higher shear strength - carry heavier building loads / sq unit of area
Loosely packed coarse grained soils exhibit less shear strength (holds less weights )
Smaller ground soils: sand, silt, clay, have an even lower shear strength and can carry less building (these are more prone to change with water)
Poorly graded soil
= well sorted - best for drainage
Sorted is inverse of graded
Well graded soil
= poorly sorted - good support, wider variety of sizes, packed in better and tight, stronger
Sorted is inverse of graded
Brownfield site
A contaminated or believed to be contaminated site
- disposal (chemicals)
- hazardous materials (underground gas tank)
- Paint factory, dry cleaners
- former mill/ oast house (kiln)
What is the angle of repose?
The steepest angle that the side of the excavated area can be before the soil backslides into the pit
- measured up from horizontal
- steeper for cohesive soils (clay)
- lower for friction soils like gravel and sand
Soldier beams
Wide flange steel beams driven into soil
- and lagging (wood boards) between each
- shoring system-keeps earth out as we dig
Methods for holding earth back during excavation
Shoring-holding dirt back - typically temporary, but may have to stay if adjacent to existing building or deep
Soldier beams
Sheeted excavation (steel sheets driven into ground- excavate between)
Trenches (modular, reusable system that is temporary instead of shoring )
Benched excavation
Soil mixing (create walls for excavation-dig holes, fill with cement, water and soil mix to create strengthened barrier wall)
Slurry walls ( used with soft earth or high ground water - economical )
Tie beam vs grade beam
The beams only tackle horizontal load. Grade beams can handle vertical roads like it a column or wall is on top)
Shallow frost protected footing
Run insulation underground next to fasting to use buildings heat to keep soil from freezing - used when we don’t excavate below frost line
Caissons
Drilled and filled - deep foundation
Can go all the way to bedrock - high bearing capacity
Can be 12’ in diameter
Sometimes 2x height of structure
Work in cohesive soils ( clay)
Piles
Hammered in - deep foundation
Sometimes you can get to depth that there is enough resistance to the hammer pushing piles in (friction) that you don’t have to go as deep as caissons
Dampproofing
Designed to resist the passage of water only in the absence of hydrostatic pressure (jv)
Waterproofing
Surface treated to resist the passage of water under hydrostatic pressure
Active vs passive methods for removing radon
Radon - second leading cause of lung cancer
Dense gas that stays low, can Pass through any material
active = fan
Alta/ A SCM survey
Shows improvements, easements, right-of-way and other things impacting land ownership (lawyers surveys )
Topographical surveys
Measures topographical changes and sometimes notable and features
Cofferdam
Temporary structure to hold back a body of water
Checkdam
Steep slope (stream or when floods) and provides a choke point - used to slow rain water and erosion
Riprap
Rock used to protect the water / land barrier and helps prevent erosion
Zoning ordinance is a variance
Zoning = rule
Variance = exception if granted)
Zoning ordinance establishes density, allowable use, parking requirements, setbacks
Variance request through A HJ
Right-of-way
Allows people to use that portion of the land for access
Easement
Allows others to control part of your land (utilities )
You can’t build on them
Easements can be placed on your land for environmental reasons
First-right-of - refusal
Giving someone first access to a site/ space usually adjacent) IF it were to become available
Eminent domain
Government can take and pay a reasonable price for property for the public good ( usually public works)
Setback
Plan - minimum requirements for a building to be away from the road, property line, or another building
Step-back
Section - requirements for buildings to step-back and allow light and air to get to the street - combat urban canyon effect.
Solar geometry
Attitude of sun
90-latitude (fall and spring equinox)
Add 15° to (90-latitude) - summer
Subtract 15 from (90° - latitude) :
Example - 40° latitude =
50° altitude at equinox
45 altitude in summer
25 attitude in winter
Economize cycle
Using outside air to help minimize heating or cooling needed (free cooling)
Green roofs
Want to be flat - upto 45°
Plat
Survey that shows boundaries / divisions of land with property rights
