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PA: Soil

Terms in this set (55)

Bedrock
Foundation: Excellent ($$); Frost: none
Clay
< .002 mm
Silt
0.002-0.05 mm
Sand
0.5-2 mm
Gravel
2+ mm
Percolation tests.
test water absorbing rate (mL/min); used for testing for septic tank, infiltration basin compatibility
soil sieve test
soil so put through series to sieves to determine grain dim
Soil load tests
- build platform, load plat w/ 2x design weight incrementally , measure settlement
Standard Penetration test (SPT)
-- measures density of granular soils ( sands ) and consistency of some clays; Soil at bottom of bore at X depth is slammed w/ weight , test records # of blows (lbs) it takes to compress soil 12"
Test pits.
- 10ft deep visual inspection of soil strata (open pits/trenches)
Proctor test
tests fill samples in lab for optimal compaction; then fill is then compacted to these standards
boring tests (aka core borings)
- cores are removed intact
- typ measure, moisture content, density, depth type of soil
- STP Standard penetration test
- measure density of granular solid and consistency of some clays'; hammer test
- Bores typ taken at corners of bldg
Clay
- Expands when wet
- Subject to slippage,
- poor for foundations unless kept dry
- poor for landscaping
- poor for sewers
- some cohesion, tensile strength, plastic when wet
- swell when they absorb water; shrinks when dry- stable clays can be used for foundations
- should be mixed w/ other mat'l
- Bentonite. - absorbent clay that when at capacity forms a water tight barrier.
Silt
- Stable when dry or damp
- Unstable when frozen
- Compresses under load
- Build under this or have responsive, flexible structure
- Behave as granular, sometimes plastic (prob depending on water content)
Gravel & Sands
- Good for bearing construction loads
- Good for sewer drainage
- Not 4 landscaping- Granular, non plastic
Solid Rock
- Highest bearing capacity
- non plastic

- Shale and slate - soft rocks w/ fine texture (2nd highest bearing capacity)-
Boulder. - rocks that have broken from bedrock-
Bedrock. - solid part of earth's crust, best foundation mat'l
Liquefaction
a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction occurs in saturated soils. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other
Hardpan
unbroken mix of clay, sand gravel. Good for foundations
Plastic Limit
The moisture content at which a soil starts deforms plastically: how it can be stretched without cracking, breaking
Liquid Limit
The minimum moisture content at which the soil will begin to flow, not retain it's shape when subjected to a small shearing force
Plasticity Index
The difference between the liquid limit and the plastic limit. >15 is expansive soil
frost heave
upwards swelling of soil during freezing conditions -- caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil
GW
Well-graded gravel
Foundation: Excellent; Frost: none
GP
poorly graded gravel
Foundation: Good; Frost: none
GM
silty gravel
Foundation: Good; Frost: slight
GC
clayey gravel
Foundation: Good; Frost: slight
SW
well-graded sand
Foundation: Good; Frost: none
SP
poorly graded sand
Foundation: Fair; Frost: none
SM
silty sand
Foundation: Fair; Frost: slight
SC
clayey sand
Foundation: Fair; Frost: medium
CL
lean clay--clay of low plasticity
Foundation: Fair; Frost: medium
ML
Silt (LL)
Foundation: Fair; Frost: very high
OL
organic silt, organic clay (organic, Low LL)
Foundation: Poor; Frost: very high
CH
clay of high plasticity, fat clay (clay, High LL)
Foundation: Very Poor; Frost: medium
MH
silt of high plasticity, elastic silt (silt, High LL)
Foundation: Poor; Frost: very high
OH
organic clay, organic silt (organic, High LL)
Foundation: Very Poor; Frost: medium
C
clay
Foundation: Fair-Very Poor; Frost: medium
M
silts
Foundation: Fair-Poor; Frost: very high
S
sands
Foundation: Good-Fair; Frost: none-slight
G
Gravels
Foundation: Excellent - Good; Frost: none-slight
O
Organics
Foundation: Poor- Not Suitable; Frost: med - not suitable
H
High Liquid Limit
L
Low Liquid Limit
W
well-graded soil
P
Poorly-graded soil
Pt
Peat
PT
peat
liquid Limit
a basic measure of the critical water contents --the point at which soil changes from the plastic state to the liquid state (clays only)
shear strength
Ability to resist failure under loading (internal friction + cohesion)
Cohesion
Mutual attraction b/t particles due to moisture content
· Sands, gravels, typ cohesionless;
· Clays, typ high cohesion, low internal friction
Water Table
depth at which soil is saturated w/ water; typ follows slope of grade; high water table = 6' - 8' below grade
Fine Grained soils
Fine-grained soils more affected by freeze-thaw cycle
Coarse-grain soils
drain better, therefore are less affected by freeze-thaw cycles
Sedimentry Rock
types of rock that are formed by the weathering of preexisting rocks and the subsequent transportation and deposition of the weathering product
Foundation: Excellent ($); Frost: none
Bedrock
solid part of earth's crust, unbroken hard rock, not over any other mat'l; best foundation mat'l for high loads
Foundation: Excellent ($$); Frost: none
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