Site Flashcards
Buoyant upload forces
when underground water pushes up on a building
plastic limit
how much water a soil can absorb before starting to expand
liquid limit
how much water until a soil starts flowing
Shear strength (for soil)
soil shear strength is the resistance of particles sliding over each other due to friction or interlocking and possible cementation or bonding
- Densely packed coarse grain solid exhibit higher shear strength
- Loosely packed coarse grained soils exhibit less shear strength
- Smaller grained soils (sand clay silt) have and even lower shear strength and can carry less building
most to least competent earth materials for supporting a building
Most to least competent for supporting a building: Gravel, Sand, Silt, Clay
Clay changes its structural behavior most over time
Clay is cohesive aka relies on stickiness for strength, sand and gravel are frictional
strategies for excavation
Soldier beams, sheeting, shoring, benched excavation
Soil mixing
excavation strategy
mix cement and water with soil along perimeter, forming columns of strengthened soil
Slurry wall
excavation strategy
While a trench is being excavated to create a form for a wall, it is simultaneously filled with slurry (usually a mixture of bentonite and water). The dense but liquid slurry prevents the trench from collapsing by providing outward pressure. Once a particular depth of trench is reached, a reinforcing cage is lowered into the slurry-filled pit and the pit is filled with concrete from the bottom up using tremie pipes. The heavier concrete displaces the bentonite slurry, which is pumped out, filtered, and stored in tanks for use in the next wall segment, or it is recycled
how to deal with excavating under the water table
Watertight enclosure (bathtub)
Pump water out of the excavation or next to the excavation
what to consider when deciding what foundation to build?
Soil bearing capacity, construction schedule, contractors recent experience, cost, groundwater conditions, effect on adjacent buildings, frostline depth
wall footing
type of spread footing
also called a strip footing, has a crawlspace or basement
column footing
type of spread footing
good for point loads, may need to brace them to eachother at grade with grade beams
can do cantilevered or combined footings with it
combined footing is good for dealing with property lines
slab on grade
type of spread footing
low loads, don’t have to worry about frost
mat foundation
type of spread footing
a continuous slab resting on the soil that extends over the entire footprint of the building, thereby supporting the building and transferring its weight to the ground
can handle heavier loads than slab on grade
floating foundation
type of spread footing
boxlike rigid structures set at such a depth below ground that the weight of the soil removed to place it equals the weight of the building; thus, once the building is completed, the soil under it will bear the same weight
when do you use piles vs caissons?
when there is no cohesive soil
pile cap
transfers load to a group of piles
minipile or helical pile
use to shore up an existing building where excess vibration associated with ramming piles would be a problem or in or near a building where quiet is desired and the ramming noise would be disruptive or anywhere where large amounts of soil displacement wont fly
reasons to underpin an existing foundation
Building renovation makes new building heavier
Existing foundation was never sufficient and needs to be improved
Adjacent sitework weakened you foundation
ways to improve an existing foundation
Extend the foundation to some deeper strata with more competent support
Make the foundation wider so that it rests on more soil
Improve the earth with imported fill or grout
3 types of foundations you can add to existing foundations
new foundation footing beneath existing
underpinning with new piels below
minipiles below
how do you keep a basement dry?
- Well maintained gutters, roof drains, downspouts
- Some place to discharge roof water far away and downhill of the building
- Sloped site away from the building to bring the surface rainwater away
- A break in the soil so that water that would otherwise press against the foundation wall will instead drop (uses drainage mat or gravel fill)
- A perforated pipe to accept the water and carry it on
blindside waterproofing
installed before the foundation and foundation wall. The waterproofing membrane is applied to the soil support (i.e. shoring, sheet pile, slurry wall, rocks, neighboring building) and then concrete or shotcrete is applied against the membrane.
good if there is a closely neighboring building
what makes foundations overly expensive?
Foundations below the water table where the excavation has to be waterproofed or continually pumped dry
Structural geometry with point loads on columns or linear loads on walls too high for shallow foundations on soil, must instead use deep caissons or piles
Foundations that interfere with a neighboring buildings foundation
retaining walls
not laterally braced by a building so need to counter overturning, sliding, and undermining
- deadman wall
- foundation with key
- earth reinforcing
- reinforced CMU with key
radon active & passive solutions
Active - any system using a fan
Passive - natural ventilation, put gravel under floor and a pipe for radon to pass through, provide extra sealing of radon routes, pressurize building & depressurize under slab gravel
max cross slope for an exterior ramp
1:48
ramp max slope, rise, and segment
1:12
30”
30’
max run for exterior stairs
12’
when do you need a guard rail?
when you’re more than 30” above the surface below
fire lane critical dims
atleast 20’ across
atleast 10’ away from building overhang
If it needs to turn, outside turning radius of 54’, inside turning radius of 30’
Carry atleast 35 tons
You need a fire lane when your building can not be reached around by 150’ hose
Geotechnical or subsurface reports
geotechnical investigation consists of gathering information about the properties of the soil and rock makeup of the property that are used when designing foundations or any other structures that require earth disturbance for any structures onsite. A geotechnical investigation can help to anticipate subsurface conditions and determine how the soil will respond to the proposed changes. This investigation is typically required to obtain a building permit for a construction project.
liquefaction
when a soil (or any particulate) behaves like a liquid due to applied stresses. Some hydration is required, and will vary by the type of soil. The most common occurrence of soil liquefaction is during earthquakes.
solar envelope
shape of your building massing that will not shade adjacent buildings
hot humid climate strategy
capitalize on breeze and don’t locate close together
hot arid climate strategy
no breeze to capitalize on, place buildings close together in order to shade, or build shading element around the building
Storm Water Pollution Prevention Plan
exempt for small projects but typically required by EPA if your projects disturb at least one acre of land
Must comply with national pollutant discharge elimination system NPDES
Cut and fill
In earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments to minimize the amount of construction labor
Metes & bounds
the term for the boundaries, property lines, or limits of a parcel of land, as defined by distances and compass bearings
Vapor extraction (site remediation)
extract contaminant vapors from below ground for treatment above ground
biodegradation (site remediation)
a process that attempts to accelerate the natural biodegradation process by providing nutrients, electron acceptors, and competent degrading microorganisms that may otherwise be limiting the rapid conversion of contamination organics to innocuous end products.
In situ incineration (site remediation)
in situ burning, or ISB, is a technique sometimes used by people responding to an oil spill. In situ burning involves the controlled burning of oil that has spilled from a vessel or a facility, at the location of the spill
Photolysis (site remediation)
the breakdown of any particular substance in presence of light
In situ aeration (site remediation)
Soil venting is a term used for an in situ aeration process that is a powerful remediation technology for the treatment of soils exposed to a variety of hydrocarbons
Biological barriers / filters (site remediation)
In situ bioreactive barriers, also known as biobarrier or biowall systems, are a bioremediation approach used to prevent further transport of a contaminant plume in the saturated zone
Gas chromatography
in environmental science GC methods are mainly used for: identifying organic pollutants in recent sediments,
What does a retention pond do?
prevents excess stormwater runoff on a site from overloading the storm sewer system by temporarily holding the water and releasing it at a controlled rate
what does a bioswale do?
allows sediment to settle while water drains into the ground
what does an infiltration basin do?
retains stormwater until it can seep into the ground
What is the max recommended slope for paved parking?
5 or 6%
What strategy do you use when water is contaminated by inorganic materials?
soil washing/soil flushing
In soil flushing, we inject water into the soil
In soil washing, we’ll excavate the soil out of the ground and wash off the contaminates, and then return the soil to the hole we dug.
When should you use Soil Solidification/Stabilization?
To address inorganic and radioactive pollutants . . . like toxic heavy metals, pesticides, and fertilizers
Mixes a soil binder with the on-site dirt to make the soil more solid and stable
When should you use soil vapor extraction?
Soils contaminated by fuels and underground VOCs (but not useful for much else)
Wells dug into the soil pull contaminated vapor out with vacuum suction where it is filtered with activated carbon at the surface.
When should you use bioremediation?
Bioremediation can be used for VOCs, fuels, inorganics (toxic metals), and explosives.
In bioremediation, we inject helpful microbes into the soil that “eat” the contaminant, rendering it less harmful or inert altogether.
What does a vertical crack in a concrete foundation mean? A diagonal crack? A horizontal crack?
Vertical crack: Not a serious problem (typically). Caused by shrinkage as the concrete cures. Typically not one long crack, but may be several smaller hairline, cracks. They may have to be sealed to prevent leaks.
Diagonal crack: Often a problem. Caused by differential settlement. Click here
Horizontal crack: A big problem. Caused by shear failure. What is an example of shear failure? The foundation wall is no longer supported: Imagine the basement wall punches into the footing under load. . . or the ground bulges around the foundation wall as the footing displaces the soil it rests on.
Where on a hill do you place a building in a hot-humid climate?
top of the hill
Where on a hill do you place a building in a temperate climate?
mid-upper part of hill
Where on a hill do you place a building in a cold climate?
mid-lower part of hill
Where on a hill do you place a building in a hot-arid climate?
bottom of hill
