D10 particle size means

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The City College of New York
Department of Civil Engineering
CE 345: Soil Mechanics
Instructor: Dr. George Mylonakis
LAB EXPERIMENT #3A:
SIEVE ANALYSIS
G
rain size analysis is a process in which the proportion of material of each grain size present i
n a given soil
(grain size distribution) is determined. The grain size distribution of coarse
-
grained soils is determined
directly by
sieve analysis
, while that of fine
-
grained soils is determined indirectly by
hydrometer
analysis
. The grain size distrib
ution of mixed soils is determined by
combined sieve and hydrometer
analyses.
T
he grain size analysis is presented as a semilog plot of percent finer versus particle size, called a
grain
size distribution curve
. A semilog plot is used for the particle s
izes to give both small and large diameters
as nearly equal weight as possible. Percent finer is always plotted as the ordinate using an arithmetic scale.
F
rom the grain size distribution curve, grain sizes such as D10, D30 and D60 can be obtained. The
D refers
to the size, or apparent diameter, of the soil particles and the subscript (10, 30, 60) denotes the percent that
is smaller. For example, D10 = 0.16 mm means that 10 percent of the sample grains are smaller than 0.16
mm. The D10 size is also ca
lled the
effective size
of the soil.
A
n indication of the spread (or range) of particle sizes is given by the
coefficient of uniformity (C
u
)
,
which is defined as
D60
C
u
=
D10
The
coefficient of curvature (C
c
)
is a measure of the shape of the curve
between the D60 and D10 grain
sizes, and is defined as
(D30)
2
C
c
=
D60 * D10
Note:
You will plot the grain size distribution curve and calculate
C
u
and
C
c
for combined analysis (with
the result of sieve and hydrometer analysis).
Introduction
A
sieve analysis consists of passing a sample through a set of sieves and weighing the amount of material
retained on each sieve. Sieves are constructed of wire screens with square openings of standard sizes. The
sieve analysis is performed on material r
etained on an U. S. Standard No. 200 sieve. Table 1gives a list of
the U. S. Standard sieve numbers with their corresponding size of openings.
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Table 1. U. S. Sieve Numbers and Associated Opening Sizes
Sieve No.
Opening Size (mm)
Sieve No.
Opening Size
(mm)
4
4.75
35
0.500
5
4.00
40
0.425
6
3.35
45
0.355
7
2.80
50
0.300
8
2.36
60
0.250
10
2.00
70
0.212
12
1.70
80
0.180
14
1.40
100
0.150
16
1.18
120
0.125
18
1.00
140
0.106
20
0.85
200
0.075
25
0.71
270
0.053
30
0.60
400
0.038
Apparatus
1.
Sieves, a bottom pan and a cover
2.
A balance sensitive to 0.1g
3.
Mortar and rubber pestle
4.
Oven
5.
Mechanical sieve shaker
6.
Paint brush for cleaning sieves
7.
Sample splitter or riffle
Preparation of sample
T
he material to be treated is first air
-
dried,
after which the aggregates present in the sample are thoroughly
broken up with the fingers or with the mortar and pestle. The specimen to be tested should be large enough
to be representative of the soil in the field. It should also be small enough not to
overload sieves. Large soil
samples are divided by using a riffle to preserve their grain
-
size distribution. The size of a representative
specimen depends on the maximum particle size. Table 2 gives some guidelines for selecting the minimum
sample weight.