Lesson 2: Physical Properties Flashcards
it is composed of solids, liquids, and gases
soil
it may be minerals, organic matter, or
both
solid phase
the spaces between the solids (soil particles)
voids
often the predominant liquid
water
often the predominant gas
air
it plays a very important role in the behavior of soils under load; also called the porewater
soil water
if all voids are filled with water
saturated
if all voids are filled with air
dry
the ratio of the amount of water (Ww) in the soil (Ws) and expressed as a percentage
water content, w
the ratio of the volume of void space to the volume of solids; this void ratio is usually expressed as a decimal quantity
void ratio, e
the volume of soil per unit volume of solids; this equation is useful in relating volumes
specific volume, V’
the ratio of the volume of voids to the total volume; usually expressed as a percentage
porosity, n
for coarse-grained soils:
the maximum and minimum porosities would be _____
48% and 26%, respectively
for coarse-grained soils:
the maximum and minimum void ratios of _____
0.91 and 0.35, respectively
the void ratios of real coarse-grained soils vary between _____
1 and 0.3
_____ often have void ratios greater than 1
clay soils
used to determine the specific gravity for coarse-grained soils
volumetric flask (at least 100mL)
used to determine the specific gravity for fine-grained soils
50-mL density bottle (stoppered bottle)
the ratio of the volume of water to the volume of voids, often expressed as a percentage
degree of saturation, S
S = 1 or 100%, the soil is _____
saturated
If S = 0, the soil is _____
bone dry
the weight of soil per unit volume (bulk unit weight)
unit weight
the weight of soil can be expressed in terms of:
- weight of soil solids
- moisture content
- total volume
what are the special cases of unit weight?
- saturated unit weight (S = 1)
- dry unit weight (S = 0)
- effective or buoyant unit weight
the ratio of the soil’s unit weight to that of water, which for a saturated soil is (γsat/γw); this ratio is a dimensionless quantity; indicates how much soil is heavier than water per unit volume or termed as the unit weight ratio or density ratio
Rd
void ratio (e) of loose uniform sand
0.8
void ratio (e) of dense uniform sand
0.45
void ratio (e) of loose angular-grained silty sand
0.65
void ratio (e) of dense angular-grained silty sand
0.4
void ratio (e) of stiff clay
0.6
void ratio (e) of soft clay
0.9-1.4
void ratio (e) of loess
0.9
void ratio (e) of soft organic clay
2.5-3.2
void ratio (e) of glacial still
0.3
an index that indicates the degree of packing between the loosest and densest possible state of coarse-grained soils as determined by experiments
relative density, Dr
e-max stands for
maximum void ratio (loosest condition)
e-min stands for
minimum void ratio (densest condition)
e stands for
current void ratio
what is the description of a coarse-grained soil with relative density of 0-20% and porosity of 100-80%
very loose
what is the description of a coarse-grained soil with relative density of 20-40% and porosity of 80-60%
loose
what is the description of a coarse-grained soil with relative density of 40-70% and porosity of 60-30%
medium dense
what is the description of a coarse-grained soil with relative density of 70-85% and porosity of 30-15%
dense
this is similar (not identical) to relative density
density index, Id
this is a ratio of the volume of excavated material to the volume of in-situ material (sometimes called borrow pit material or bank material)
swell factor, SF
clay minerals with 45-145% free swell
calcium montmorillonite (Ca-smectite)
clay minerals with 1400-1600% free swell
sodium montmorillonite (Na-smectite)
clay minerals with 15-120% free swell
illite
clay minerals with 5-60% free swell
kaolinite
give the ten weight-volume relationship
- water content, w
- void ration, e
- specific volume, V’
- porosity, n
- specific gravity, Gs
- degree of saturation, S
- unit weight
- relative density, Dr
- density index, Id
- swell factor, SF
give the four distinct states of fine-grained soil
in order of increasing water content
* solid
* semi-solid
* plastic
* liquid
described as the original liquid state; as the soil dries, its water
content reduces and so does its volume
point A
the soil becomes so stiff that it can no longer flow as a liquid
point B
the boundary water content at point B
liquid limit (LL)
the water content at which the soil changes from a plastic to a semi-solid
plastic limit (PL)
the soil at point C or plastic limit (PL) is said to exhibit _____ or the ability to deform continuously without rupture
plastic behavior
the state of the soil if drying is continued beyond the range of water
content for plastic behavior
semisolid
the range of water contents over which the soil deforms
plastically
plasticity index (PI)
as the soil continues to dry, it comes to a final state; at this state, no further volume change occurs because nearly all the water in the soil has been removed
solid state
the point where the water content at which the soil changes from a semisolid to a solid
point D or the shrinkage limit (SL)
useful for the determination of the swelling and shrinking capacity of soils
shrinkage limit (SL)
the range of water content from the plastic limit to the shrinkage limit for which the soil behaves as a semisolid
shrinkage index (SI)
he developed a method to describe the consistency of fine-grained soils with varying ω
Albert Atterberg
what are the four basic states or behavior of the soil?
- solid
- semi-solid
- plastic
- liquid
phase between solid and semi-solid
shrinkage limit (SL)
phase between semi-solid and plastic
plastic limit (PL)
phase between plastic and liquid
liquid limit (LL)
what are the index parameters?
- plasticity index
- liquidity index
- shrinkage index
moisture content after 25 blows or moisture content at which a soil changes from the liquid state to the plastic state
liquid limit (LL)
a liquid limit device used to determine the liquid limit (LL) from an apparatus that consists of a semispherical brass cup that is
repeatedly dropped onto a hard rubber base from a height
of 10mm by a cam operated mechanism
casagrande cup
he developed the liquid limit device known as casagrande cup
Arthur Casagrande (1932)
the moisture content in percent at which the soil crumbles, when rolled into threads of 3.2mm (1/8”) in diameter
plastic limit (PL)
relative consistency of a cohesive soil in the natural state; the ratio of the difference in water content between the natural or in-situ water content of a soil and its plastic limit to its plasticity index
liquid index (LI)
what is the soil strength if LI < 0?
semisolid state: high strength, brittle (sudden) fracture is expected
what is the soil strength if 0 < LI < 1?
plastic state: intermediate strength, soil deforms like plastic material
what is the soil strength if LI > 1?
liquid state: low strength, soil deforms like viscous fluid
it is analogous to viscosity in liquids and indicates internal resistance to forces that tend to deform the soil
soil consistency or consistency
what are the sources of internal resistance that tend to deform the soil?
- inter-particle forces (cohesion or adhesion)
- cementation
- inter-particle friction
- soil suction
Consistency changes with _____
water content
a measure of consistency is provided by _____
consistency index
what is the description of fine-grained soils if the consistency index < 0.25?
very soft (ooze out of finger when squeezed)
what is the description of fine-grained soils if the consistency index is between the range of 0.25-0.50?
soft (easily molded by finger)
what is the description of fine-grained soils if the consistency index is between the range of 0.50-0.75?
firm or medium (can be molded using strong finger pressure)
what is the description of fine-grained soils if the consistency index is between the range of 0.75-1?
stiff (finger pressure dents soil)
what is the description of fine-grained soils if the consistency index > 1?
very stiff (finger pressure barely dents soil, but soil cracks under significant pressure)
used describe the importance of the clay fractions on the plasticity index
activity (A)
clay-rich soil with activity of <0.75
inactive
clay-rich soil with activity between 0.75-1.25
normal
clay-rich soil with activity between 1.25-2
active
clay-rich soil with activity of >6
very (highly active)
minerals with activity between 0.3-0.5
kaolinite
minerals with activity between 0.5-1.3
illite
minerals with activity between 4-7
Na-montmorillonite
minerals with activity between 0.5-2.0
Ca-montmorillonite
one of the factors used in identifying expansive or swelling soils
activity
when A < 0.70, clay is classified as _____
inactive clay
when 0.7 < A < 1.20, clay is classified as _____
normal clay
when A > 1.20, clay is classified as _____
active clay
a line that separates the inorganic clays from the inorganic silts
a-line
a line that approximately the upper limit of the relationship of the PI and LL
u-line
fine-grained soils can exist in one of four states, namely: _____
- solid
- semi-solid
- plastic
- liquid
agent that is responsible for changing the states of soils
water
a soil gets weaker if its water content _____
increases
three limits based on the water content that causes a change of state
- liquid limit
- plastic limit
- shrinkage limit
the limit where the water content that caused the soil to change from a liquid to a plastic state
liquid limit (LL)
the limit where the water content that caused the soil to change
from a plastic to a semisolid
plastic limit (PL)
the limit where the water content that caused the soil to change from a semisolid to a solid state
shrinkage limit (SL)
defines the range of water content for which the soil behaves like a plastic material
plasticity index (PI)
gives a qualitative measure of strength
liquidity index (LI)
the soil strength is lowest at the _____ and highest at the _____
liquid state; solid state
