Physical properties of
riversand;
The
sieve analysis is graphically
represented in fig 1.the curve of fig1a. gives the amount of sand by weight
that is retained on a sieve of the lower mesh number1b. gives the weight of
sand all passing through a corresponding sieve,
the terms of percentage fraction of the total weight.
The
quantity of mica by weight is through quite small , its presence may give some
elastic properties to the sand mass and influence compaction and shear
–strength.
It
is seen from the curves that the sand is medium and fine ; it mostly consists
of particles of size about 0.26mm.The Allen hazen’s most representative size,
commonly called the effective size D10 is 0.23mm.the uniformly
co-efficient cu , which is the ratio of the maximum size of the
smallest 60% to the effective size is 1.8. it is, there for ends, a fairly
uniform sand. the grain size distribution curve each for the Daytona beach and
port said beach sands is reproduced for comparison fig2.the grain size distribution of jamna
sand is almost similar to them both, but otherwise it consist of coarse
particles.
The
sand is grey –black in colour If gate at ordinarily in aggregate, but the
various sieved fraction exhibits a change in colour . the coarse fractions show
a darker shade then the finer fractions. on examining under a microscope it is
found to consist of clear transparent and opalescent size white particles mixed
with block, grey, yellow, brown and mauves particles mostly opaque. The number of uncolored partials in finer fractions leads to the
conclusion that the coloured material is stronger then the uncolored. the
grains are all quite irregular in shape. the angle of repose for different
fractions varies from 350-370
Compaction
of the sand is obtained by means of a hammer of 6Ib. falling through a vertical distance of one foot on
sand placed in a cylindrical container which is made in two parts as usual; the
upper part being detachable in the form of a ring from the lower actual
container. The latter has a capacity of
1/ 120ft.
The diameter of the container was only slightly more than that of the hammer to
allow clearance for free movement. The hammer, therefore,
strikes
the whole surface of the sand each time thus giving more uniform compaction than is obtained by the conventional design. Each stroke
of the hammer delivers
an
energy of6 foot pounds
No
of sieve retaining the sand
|
Percentage of grains of various
colours
|
|||
Clear
transparent.
|
opalescent
|
Lightiy
coioured;brownish
|
Dark
coloured: grey, black
|
|
30
|
45
|
10
|
15
|
30
|
52
|
60
|
8
|
12
|
20
|
72
|
68
|
6
|
12
|
14
|
85
|
74
|
5
|
8
|
13
|
The
curves in fig.3 represent the variation of bulk density of the different
fractions of jamna sand against compaction. Almost maximum compaction is
reached at 15 strokes of the hammer.
More hammering does not appreciably increase the bulk density. The maximum
density obtained is 92·5 lb./ft.3. The actual
solid density, as calculated from the specific gravity value of 2·7, comes out to be 170 lb./ft.8 nearly. The value of 92·5 lb./ft.3 seems to be quite low and
may partly be due to arching of sand grains in the container. The maximum and minimum bulk density for the whole dry sand is 96 and 78 lb./ft.3 and corresponds to a porosity of 42%
to 54% respectively.
J. Kolbuzewski (1950) has shown that porosity varies from 36% to 47% for Leighton Buzzard sand under different con- ditions of deposition.
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