||THE COOPER UNION
Albert Nerken School of Engineering
Soil Mechanics Laboratory
Experiment No. 3 - Grain Size Distribution Analysis
||To determine the grain size distribution of a soil.
1) "Soil Testing for
Engineers" by T. W. Lambe; Chapter IV.
2) "Engineering Properties
of Soils and Their Measurements", 4th edition by
Joseph E. Bowles; Experiments No. 5 & No. 6.
3) A.S.T.M. Standards, 1978, Part
19; Designation D422-63, D1140-54.
||APPARATUS AND REAGENTS:
1) Soil Hydrometer (range 0.995 -
2) Mechanical mixer.
3) Graduate (1000 ml.).
4) Electronic top loading balance
(sensitive to .01 gm.).
5) Triple-beam balance (sensitive
to 0.1 gm.).
6) Electric oven.
7) Thermometer (sensitive to
8) Set of U. S. Series sieves
containing the following sizes:
1-1/2", 1", 3/4", 1/2",
and Nos. 4, 10, 16, 30, 60, 100 and 200.
9) Miscellaneous apparatus and reagents,
sieve pans, etc.
||1) Select a representative sample of
the soil as close to its natural moisture content as
possible, amounting to approximately 500 gms. of
equivalent oven dry material and place in a pan.
Separate this soil sample into coarse, and fine
fractions, using the following procedure:
a) Set up a No.4 and No. 10 sieve
and a pan.
b) Take approximately a 50 gm.
portion of the sample and gently grind it in a
mortar using a rubber covered pestle. Make certain
that none of the individual grains are crushed.
c) Transfer this material to the
No. 4 sieve and using a stiff brush and the fingers,
work it through the sieve. Be extremely careful to
see that every soil grain retained in this sieve is a
discrete particle and not an aggregation of finer
particles. This condition is very common in soils
with plastic fine fractions where grinding in the
mortar and pestle has not been sufficiently thorough.
It will probably be necessary to examine many grains
individually by attempting to crush them between the
fingers, to properly test for this condition.
d) Remove the No. 4 sieve and set
aside the material retained on it (+No. 4 material)
in an evaporating dish.
e) Follow the procedure of (c)
for the material remaining on the No. 10 sieve;
observe the caution mentioned in (c) even more
diligently, since the soil grains are much smaller in
size and the detection of these aggregations of
particles will be more difficult.
f) Remove the No. 10 sieve and
set aside the -No. 4 to +No. 10 material in another
g) The sieve pan now contains the
material passing the No. 10 sieve (-No. 10 material).
Leave it in this pan.
h) Repeat steps (a) to (g)
inclusive a sufficient number of times to separate
the entire 500 gm. sample into the three fractions
+No. 4, -No. 4 to +No. 10, and -No. 10.
i) Place the +No. 4 and -No. 4 to
+No. 10 samples in the electric oven at 110oC.
||3) Record the weight of a
crystallizing dish and watch glass in Table 1, and the
weight of the sieve pan in Table 2.
Weigh the fine fraction (-No. 10 material) plus the pan
to 0.1 gm. on the triple-beam balance; record in Table 2
and compute the total weight of the wet fine fraction.
5) Take approximately 20 gm. of the
fine fraction and place in the weighed crystallizing dish
and watch glass of step 3. Place the remainder of the
fine fraction in a tightly covered labeled jar.
6) Weigh the crystallizing dish and
watch glass plus the soil sample to 0.01 gm. on the
electronic top loading balance and record in Table 1.
7) Remove the watch glass and place
beneath the crystallizing dish and put both of them,
together with the soil sample, in the electric oven at
110oC. If some soil has adhered to the glass,
place the glass beside the crystallizing dish in the oven
for at least 6 hours.
8) Remove the crystallizing dish and
watch glass from the oven and cover the soil sample with
the watch glass so that it will not absorb moisture from
the atmosphere. Place the container in a dessicator to
cool, remove the container from the dessicator and weigh
to 0.01 gm. on the electronic top loading balance and
record the weight in Table 1.
9) Compute the moisture content of
the fine fraction, and record in Table 1.
10) Perform a sieve analysis on the
coarse fraction (+No. 10 material) in the following
a) Remove the +No. 4 and -No. 4
to +No. 10 material from the oven. Because of the
fact that almost all of the surface area of each of
these relatively large particles is exposed to heat,
the drying will be quite rapid.
b) Set up a nest of sieves that
include the following sizes: 1-1/2", 1",
3/4", 1/2", 3/8", and No. 4 sieves and
c) Deposit the +No. 4 material
obtained in steps 2 (a-e) on the 1-1/2" sieve
and work the material through the sieve.
d) Place the material retained on
the 1-1/2" sieve in a weighed evaporating dish
and weigh the evaporating dish and the 1-1/2"
material on the triple-beam balance to 0.1 gm.;
record this weight in Table 3 as the weight retained
on the 1-1/2" sieve.
e) Set this 1-1/2" material
aside in a tightly covered labeled jar.
f) Repeat step (c) for the
material retained on each of the 1", 3/4",
1/2", 3/8" and No. 4 sieves. Deposit the
material retained on each of these sieves in the jar
g) If any material should pass
the No. 4 sieve at this time, it merely indicates
that the operations of step 2 (c) was not carried out
too carefully. Add such material to the -No.4 to +No.
10 material which has been removed from the oven.
h) If any material apparently
finer than the No. 10 sieve should appear in the -No.
4 to +No. 10 material at this time, this -4 to +No.
10 material should be put through a No. 10 sieve
again and any -No. 10 material thus obtained should
be added to that of step 4 and a correction made in
i) Weigh this total -No. 4 to
+No. 10 on the triple-beam balance and record in
Table 3 as the weight retained on the No. 10 sieve.
j) Mechanical sieve shaker may also be used
to separate different grain sizes.
||11) Empty the contents of the jar of
steps 10e, f and h into the evaporating dish, weigh and
record in Table 2.
12) As a check,
compare the sum of the weights retained on each of the
1-1/2", 1", 3/4", 1/2", 3/8" #4
and #10 sieves with the value of step 11.
13) Calibrate the hydrometer and the
1000 ml. graduate using the following procedures:
a) Determine the cross-sectional
area of the 1000 ml. graduate by measuring the
distance in cm. between any two graduations on the
graduate, e.g., the 100 ml. and 900 ml. graduations;
cross-sectional area, A, is equal to the volume
included between these two graduations divided by the
measured distance between the two graduations. Record
the value of this area in Table 6.
Note: Should use same
cylinder in Step 18.
b) Determine the volume of the
hydrometer bulb. Add 500 ml. of water (tap water will
be adequate for this determination), submerge the
hydrometer bulb, and observe the volume (volume of
the hydrometer bulb is the difference between the
final volume after submergence of the bulb, and the
original 500 ml. volume). Record the value of this
volume in Table 6.
c) Measure and record the
distance, H, from the neck of the bulb to any four
calibration marks well distributed along the
hydrometer stem. Record the values of H and the
corresponding hydrometer reading in Table 6.
d) Measure the distance from the
neck of the bulb to its tip and record this as h, the
height of the bulb in Table 6. For a symmetrical bulb
h/2 locates the center of volume of the bulb.
e) Compute the distances HR and
HR' from the center of volume of the bulb to each of
the four calibration marks of part (c) making use of
Formulas 1a and 1b.
f) Determine the value of the
meniscus correctiion cm, by filling the 1000 ml.
graduate with distilled water, inserting the
hydrometer and observing the difference in readings
taken at the surface of the water and the upper rim
of the meniscus; this difference is the meniscus
correction. Record the value in Table 6.
g) Determine the value of the
density correction, cd, by filling the 1000 ml.
graduate with 100 ml. of the defocculating agent and
900 ml. of distilled water, inserting the hydrometer
and taking a reading at the surface of the liquid,
and noting the difference between this reading and
the one taken at the surface of the distilled water
in (f); this difference is the density correction.
Record the value in Table 6.
||14) Select a representative sample
of the fine fraction from step 4 amounting to
approximately 75 gm.; place in a weighed evaporating
dish, and weigh dish and soil to 0.01 gm. on the
electronic top loading balance.
Record the weight of the dish and the weight of the dish
and soil in Table 5.
16) Add sufficient distilled water to
the evaporating dish to cover the soil sample with
approximately 1/4 inch of water; stir until the soil is
17) Add 100 ml. of the deflocculating
agent to this soil-water mixture, stir thoroughly, cover
the evaporating dish to retard evaporation, and allow to
soak for at least 18 hours. If it will be necessary to
allow a longer soaking period (in the case of students,
class schedules may prevent the strict adherence to the
18 hour soaking period) transfer the soil-water mixture
to a jar with a screwtype cover. This will, of course,
prevent evaporation and contamination from dust. Note
that in this transferral not a single drop of this
soil-water mixture must be lost since the soil sample
itself represents a definite weighed quantity from step
14. A wash bottle or syringe filled with distilled water
are very convenient devices for making this transferral.
18) At the end of the soaking period
transfer the soil-water mixture containing the
deflocculating agent to a 1000 ml. graduate and add
distilled water to bring the graduate total volume up to
19) The soil sample will now be given
further dispersion with the compressed air mechanical
mixer. Open the compressed air regulating valve on
this apparatus until a pressure of one p.s.i. is
registered on the gauge.
20) Insert the mechanical mixer tube in
the graduate, seat it properly at the top of the
graduate, and increase the pressure to 25 p.s.i.
21) Mix the soil sample for the
following periods of time:-
||22) At the end of the mixing
period, reduce the pressure to 1 p.s.i.
Carefully unseat the mechanical mixer tube and slowly lift
it from the graduate while simultaneously washing, with
wash bottle or syringe filled with distilled water, any
soil grains adhering to the mixer tube or injection
head into the graduate.
24) Add distilled water to the
graduate to bring the suspension level to the 1000 ml.
25) Thoroughly mix the contents
of the graduate for one minute; create a soil suspension
of uniform density using the following procedure:
a) insert the stirring rod,
consisting of a two foot-long metal rod having a
1-1/2" diameter rubber disk at one end, into the
graduate and vigorously pump the rod up and down
throughout the entire depth of the suspension, for 40
b) At the end of 40 seconds,
slowly pump the rod up and down in the upper-half of
the suspension, for 15 seconds.
c) For the last 5 seconds slowly
move the stirring rod up through the upper-half of
the suspension, and withdraw it from the graduate.
||26) At the instant that the stirring
rod is removed from the suspension start the timer,
insert the hydrometer to a depth slightly below its
floating depth, and allow it to float freely to rest.
Take hydrometer readings at elapsed times, measured from
the beginning of sedimentation, of 1/2, 1 and 2 minutes;
the hydrometer is to remain continuously in the
suspension for these two minutes. Make a record of these
27) Remove the hydrometer
from the suspension after the 2 minute reading has been
taken, wipe and dry it, and place it in its container.
28) Repeat steps 25 and 26 twice
more. It is the average of the three 1/2 minute, 1 minute
and 2 minute hydrometer readings which are recorded in
Table 7. as R'H values.
29) Additional hydrometer readings
will be taken at 4, 8, 15 and 30 minutes; and 1, 2, 4,
and 24 hours of elapsed time (all elapsed times being
measured from the beginning of sedimentation of the third
run of step 28). Times, other than these just stated, may
be substituted for the sake of convenience.
30) When it is desired to take one of
the hydrometer readings stated in step 29, carefully
insert the hydrometer in the soil suspension to a depth slightly
below its floating depth 15 to 20 seconds before the
due-time of the reading, thus allowing it to float freely
to rest (as in step 26) in time for the reading to be
taken. Record these readings as R'H values in
Table 7. Insert and withdraw the hydrometer very slowly
and carefully to cause as little disturbance in the
suspension as possible.
31) After the two-minute reading and
all subsequent readings, insert the thermometer slowly
and carefully in the soil suspension, take the
temperature, and record the values in Table 7.
32) After taking the last hydrometer
reading, transfer the soil suspension to a No. 200 sieve,
and wash with tap water until the wash water is clear.
Transfer the material retained in the sieve to an
evaporating dish and dry in an electric oven at 110oC.
33) Remove the material from the oven
and perform a sieve analysis on it in the following
a) Set up a nest of sieves
consisting of Nos. 16, 30, 60, 100 and 200.
Additional sieves may be added if desired.
b) Transfer the dried material
from the evaporating dish to the No. 16 sieve.
c) Gently sweep the material over
the surface of the screen with a fine-haired brush.
Continue brushing until not more than one per cent of
the material retained on the sieve passes that sieve
in one minute of brushing.
d) Transfer the residue on the
No. 16 sieve to an evaporating dish, weigh the dish
and soil to 0.01 gm. on the electronic top loading
balance, and record the weight in Table 4.
e) Repeat (c) for the material on
the No. 30 sieve, or whatever sieve finer than the
No. 16 is being used and now contains the material
passing the No. 16 sieve.
f) Transfer this residue to the
evaporating dish containing the residue of the No. 16
sieve, determine the cumulative weight, and record in
g) Repeat the sieving procedure
of (c) on the material on each succeeding
finer-opening sieve, transferring the residue of each
sieve to the evaporating dish containing the
previously weighed residues of the coarser sieves,
and obtaining a new cumulative weight. Record these
cumulative weights in Table 4.
1) Correct total weight of the
fine fraction sample used in the hydrometer analysis,
(step 14) to a dry weight using the moisture content
determined in step 9. Record this weight in Table 5.
2) The computations for the sieve
analysis of the material coarser than the No. 10
sieve will be made in the following manner:
a) Compute the dry weight of
the whole soil sample, coarse fraction plus fine
fraction, by adding the dry weight of the coarse
fraction (steps 11 and 12) to the dry weight of
the entire fine fraction. This dry weight of the
fine fraction is computed by correcting the total
weight of the fine fraction (step 4) for the
moisture content (step 9).
b) Compute the cumulative
weight finer than each corresponding coarse sieve
using the individual weights retained on each
sieve from step 10. Record in Table 3.
c) Compute the percent finer
than each corresponding coarse sieve by dividing
the cumulative weight finer than each sieve, (b),
by the dry weight of the whole sample, (a).
Record the values in Table 3.
3) The computations for the sieve
analysis of the material finer than the No. 10 sieve
will be made in the following manner:
a) Compute the cumulative
weight finer than each corresponding fine sieve
by subtracting each cumulative weight retained,
(step 33g) from the dry weight of the hydrometer
sample (computations-1). Record in Table 4.
b) Compute the per cent finer
than each corresponding fine sieve by dividing
the cumulative weight finer than each sieve size
by the dry weight of the hydrometer sample, and
multiplying this quotient by the per cent of the
whole soil sample that is finer than the No. 10
4) Compute the R"H
values by adding the meniscus correction (13f), to
the observed hydrometer readings, R'H, and
record in Table 7.
5) Compute the RH
values by subtracting the density correction (13g)
and applying the temperature correction, (adding or
subtracting it depending upon the temperature of the
suspension at the time of reading and the calibration
temperature of the hydrometer).
6) The computations for the
hydrometer analysis will be made in the following
a) Compute the values of the
equivalent grain size, D, in mm., corresponding
to each hydrometer reading, using Stokes Law
(Formula 3); obtain necessary values of HR
from the plot of Graphs - 1.
b) Compute the percent of the
whole soil sample that is finer than each of
these corresponding equivalent grain sizes of (a)
1) Computing the percent
of the hydrometer sample that is finer than
each of the corresponding equivalent grain
sizes, using Formula 2. To use Formula 2
values of RH, the specific gravity
of the hydrometer sample; and dry weight of
the hydrometer sample are needed. RH
values have been computed in Computations -
5; the specific gravity of the hydrometer
sample (material passing the No. 10 sieve)
has been determined in Experiment No. 2; and
the dry weight of the hydrometer sample has
been computed in Computations - 1.
2) Multiplying each of
the percents finer of the hydrometer sample,
computed in the previous step, by the percent
of the whole soil sample that is finer than
the No. 10 sieve.
1) Plot the calibration curves
for the hydrometer and graduate used in the
hydrometer analysis. Both curves will be plotted on
cartesian coordinates with the hydrometer reading as
ordinate and the corresponding distance to the center
of volume of the hydrometer bulb as abscissa. Curve 1
will be the plot of Formula la and curve 2 will be
the plot of Formula lb; values for both plots have
been computed in Experimental Procedure - 13e, and
values are recorded in Table 6.
2) Plot the grain size
distribution curve for the whole soil sample analysed
in this experiment. The data for the plot have been
computed in Computations - 2, 3, and 6 and are
recorded in Tables 3, 4, and 7. Plot the equivalent
grain size in mm. on a logarithmic abscissa vs. the
corresponding per cent finer on an arithmetic
ordinate, using a second-quadrant plot.