sedimentation test for soil..soil mechanics
TRANSCRIPT
PREPARED BY GROUP #4
Abdul Majid, Syed Izaz Ur Rahim, Ansar Ullah, Taimur Khan, Aimal Khan, Mohammad Shoaib
Hydrometer Analysis
Before starting of Hydrometer Analysis, we should know the whole procedure and Calculation of Sieve Analysis.
So here is a Outline for Sieve Analysis.
Sieve Analysis
Sieve Analysis is used for Grain Size Distribution(GSD) for grains larger than 0.075mm(75 micro m).
The grains that passed through sieve #200(>0.075mm) , so it’s size will must less than 0.075mm and greater than 0.5micro m.
Sieve analysis distribute Coarse, Fine and medium sizes But in Hydrometer analysis Silt, Clay, and Finer grains can be distributed.
It is necessary that the preparation of both two test done at a time.(If possible)
Cont…
Sieve Analysis
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
10
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100
Sieve Analysis
Sieve Analysis
Hydrometer Analysis
DEFINITION
PURPOSE
PROCEDURE
Hydrometer method is used to determine the distribution of the finer particles. Standard Reference: ASTM D 422 - Standard Test Method for Particle-Size Analysis of Soils.
Generally in Sieve analysis the soil that passes through sieve #200, that soil used for Sedimentation (Hydrometer Test).
Hydrometer Test is based on Stokes Law
Hydrometer Analysis
Cont… Hydrometer analysis is based on the principle of
sedimentation of soil grains in water.
When a soil specimen is dispersed in water , the particles settle at different velocities, depending on their shape, size, weight, and viscosity of water.
Purpose: Hydrometer test is the process by which fine-grained , clay ,and Silts are graded.
This test is performed if the grain sizes are too small for Sieve analysis.
Hydrometer Analysis
This test used for 0.075mm>D>0.5µm of particles. Procedure: Take a sample of Soil which passed through Sieve
#200.In Sieve Analysis
Hydrometer Analysis
Weight soil Sample(that passed through sieve #200) and add with distilled water to prepare a solution.
Add 125mL of dispersion agent like Sodium Hexa-meta-phosphate.
Procedure
Procedure
Transfer the soil slurry into a mixer by adding more distilled water, if
necessary, until mixing cup is at least half full. Then mix the solution
for a period of two minutes.
Immediately transfer the soil slurry into the empty sedimentation
cylinder. Add distilled water up to the mark.
Cover the open end of the cylinder with a stopper and secure it with
the palm of your hand. Then turn the cylinder upside down and back
upright for a period of one minute. (The cylinder should be inverted
approximately 30 times during the minute.)
Procedure
Set the cylinder down and record the time. Remove the stopper from the cylinder. After an elapsed time of one minute and forty seconds,
very slowly and carefully insert the hydrometer for the first reading.
(Note: It should take about ten seconds to insert or remove the
hydrometer to minimize any disturbance, and the release of the
Engineering Properties of Soils Based on Laboratory Testing hydrometer should be made as close to the reading depth as possible to avoid excessive bobbing).
Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24 hours
When a Hydrometer placed in the soil suspension at a time t measure from the start of sedimentation it measures the specific gravity in the vicinity of its bulb at a depth L.
The larger Particles would have settled beyond the zone of measurement.
Note that L is the depth measure from the surface of the water to the center of gravity of the hydrometer bulb at which the density of the suspension is measured. The value of L is change with time t.
Why L is changing?
The lower the density of the substance, the farther the hydrometer will sink. That's why L is changing.
Now L is known , t is known, the Diameter D is unknown, which can be find from the following equations
FDVTD
and D3
D2
For Diameter D=
Hydrometer Reading l(cm)
0 16.31 16.12 163 15.84 15.65 15.56 15.37 15.28 159 14.8
L=L1+1/2(L2-Vb/A)
L2=length of the hydrometer bulb=14cmVb= vol. of the hydrometer bulb=67cu.mA=cross sectional area of the sedimentation cylinder=27.8sq.cmL1=10.5cm
L=16.29-0.164R
Comparison B/W Sieve and Hydrometer Analysis
0 0.005 0.01 0.015 0.02 0.025 0.03 0.0350
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Sieve AnalysisHydrometer Analysis