Introduction:
In this lab, we experiment on the Atterberg Limits. When a cohesive soil is mixed with an
excessive amount of water, it liquefies and behaves like a viscous fluid. However, when this soil
is dried, the l
...
Introduction:
In this lab, we experiment on the Atterberg Limits. When a cohesive soil is mixed with an
excessive amount of water, it liquefies and behaves like a viscous fluid. However, when this soil
is dried, the loss of moisture will change it into a harder composite. This transition is known as
the liquid limit(LL), where the soil begins in a liquid state and changes into a plastic state. As the
moisture content gradually lessens, the soil changes from a plastic state to a semisolid state. This
is known as the plastic limit(PL). Similarly, as the soil transitions from a semisolid state to a
solid state, this is known as the shrinkage limit(SL). All three limits are known as the Atterberg
Limits.
First, we begin by testing the cohesive soil’s liquid limits. To do this we utilize the
Casagrande liquid limit device and grooving tool. First, the mass of the can is weighed( M1
¿ .
Then, soil is placed on the cup of the device, and using the grooving tool, the soil pat is separated
along the centerline. By rotating the arm of the device (about 2 rotations per second), the cup
with rise and drop, equaling one blow, and the groove along the centerline will begin to close.
When the groove closes to about 30 mm, the number of blows (N) is recorded. Partial of the soil
is taken and the moist soil( M2
¿ plus mass of can( M1
¿ is weighed. Three different tests
are taken; each have a more moisture content than the last. Then the soil is dried fro 24 hours and
its mass( M3
¿ with mass of can ( M1
¿ is recorded. Using the information received, the
moisture content in percent (w%), the liquid limit(LL), and flow index(Fi) are determined. The
moisture content can be found by using the equation:
w( )=
M2−M3
M3−M1
x100
The liquid limit can be found using log-scaled graph, where the moisture content at 25 blows is
located. The flow index can be found using the equation:
FI=
w1 −w2
logN2−logN1
To conduct the plastic limit test, we take a moist soil sample and roll it into a ball using
the palm of the hand. Then placing it on a glass plate, roll it for about 80 strokes per minute (one
roll backward and one roll forward constitutes one full strokes). When the diameter of the sample
is about 3 mm, take the mass of soil
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