CHAPTER 4
RESULTS AND A N A L Y S I S
4.1
Introduction
The analysis was done in order to find out the relationship between standard
sand and river sand for determining the in-situ density of soil of natural or
compacted fine- and medium-grained soils. The tests determine bulk density, the
moisture content of the sample which is weighed has to be representative. By
conducting this test it is possible to determine the field density of the soil. The
moisture content is likely to vary from time to time and hence the field density also.
So it is required to report the test result in terms of dry density. Other tests also
being carried out, such as laboratory compaction test, liquid limit and plastic limit
test, particle density test and particle distribution test including hydrometer
analysis. These supplement tests were done to analyze the soil that was used to fill
as the sudgrade material at the selected site of study.
When the field density tests conducted using river sand, the dry density
obtained from the selected site is higher compared to the silica sand. For all the
tests have been done, the results of the dry density are higher than when silica sand
is used for the test.
44
4.2
The Soil Classification Tests
BS 1377: Part 2: 1990 specified methods of test for the classification of soil
and for the determination of basic physical properties.
4.2.1
The Moisture Content Test
The moisture content of soils, that is the amount of water in soils can
influence their behavior. Measurement of moisture content, both in the natural
state and under certain defined test conditions, can provide an extremely useful
method of classifying cohesive soils and of assessing their engineering properties.
The moisture content of a soil is the characteristic in which is most
frequently determined, and applies to all types of soil. The types of test that
involves determination of moisture content are liquid limit, plastic limit, laboratory
compaction test and the sand replacement test.
There are four tests carried out to determine the moisture content before the
samples being used to conduct field density test. Table below shows the summary
of the moisture content test for silica sand and river sand.
Table 4.1: Moisture Content Test Result
Silica Sand
River Sand
0.14%
0.11%
0.10%
0.09%
0.12%
0.11%
0.11%
0.08%
Average = 0.12%
Average = 0.10%
45
From the result of moisture content test, the silica sand and river sand is
considered almost totally dry. The sands are used to proceed with the testing.
4.2.2
The Particle Density Test
Particle density is defined as the ratio mass of the soil particles to the mass
of the same volume of water. The value of particle density may vary among the
mineral constituents of the soil and from size fraction to size fraction. Clean sands
generally have a particle density close to 2.65 Mg/m3 and clays a somewhat higher
value around 2.72 Mg/m3 or more. Low values in natural soils would suggest the
presence of organic matter.
There are four tests carried out to determine the particle density to the silica
sand, river sand and the soil to be used for filling at the selected site. The results
were summarized in the table below.
Table 4.2: Particle Density Test Result
Particle Density
Silica Sand
for Particle Density
for
River Sand
Particle Density
use as “filled material”
at site
2.646 Mg/m3
4.2.3
2.637 Mg/m3
Liquid Limit, Plastic Limit and Plasticity Index
2.715 Mg/m3
46
When a soil contains an appreciable quantity, say 20 percent or more by
weight, of material finer than 0.063 mm size a description based on size distribution
alone is
insufficient. The size distribution of clays and silts is of interest, the behavior of clay
is related to its mineralogical composition, water content and the micro- and
macro-fabric of its particles. The change in the state of clay as the water content is
changed has been found to be a useful and simple way of distinguishing one clay from
another and this is the basis of soil classification applied to clays.
The coarser soils may contain just sufficient fine material that when moist a
cohesive mass of the soil can be formed. With a greater content of fines or more
clay sizes among them the soil may show plasticity. The fine fraction of a coarse
soil can thus usually be distinguished as either non-plastic or plastic.
The result of liquid limit and plastic limit test of the “filled material” is as
below:
Liquid limit = 63%
Plastic Limit = 41%
Plasticity Index = 63% -41%
= 22%
Soil Type = MH
The result of the soil test shows that it is classified as Silt High.
4.2.4
The particle Size Distribution Test Including Hydrometer Analysis
The most common particle size distribution curves are plotted in the
cumulative diagram displaying the percentage by weight of the material finer than
47
any given size. It is being presented on a logarithmic scale. When the particles are
matched against sieves of known aperture sizes a satisfactory estimate of the
amounts of material finer than each size is easily obtained. The lower limit of size
analyzed by sieving is usually fine sand at 0.063 mm.
The particle size distribution of the silty fractions of soil is of interest and
these sizes lie below 0.063 mm. The size distribution over the silt range is
in-directly assessed from determinations of the velocities of sedimentation of the
particles in water. The silts reach their terminal velocity almost immediately and
thereafter fall in water at a constant velocity, which, for the silt sizes, is proportional
to the square of the particle diameter.
Soils with similar size distribution curves would in a general sense be
expected to show similar engineering characteristics. Predictions of behavior are
made cautiously because the size distribution alone does not convey the
arrangement and density of packing of the particles and other factors which
influence the behavior of the soil.
The fine grains in a soil exercise the largest influence on its behavior. The
effective size or ten percent size (D 10) is used in describing soils. The steepness of
the curve is given a numerical value in the uniformity coefficient Cu. If the range of
sizes present in a soil is small it is described as a uniform soil or uniformly graded.
Such poorly graded soils will have Cu values of 2 or less. Some poorly graded soils
may have a deficiency of intermediate sizes and are described as gap graded. A
well-graded soil is one which can give a dense, rather strong soil. It will have a
wide range of particle sizes and the distribution curve will be smooth and concave
upwards, with no deficiencies or excesses of sizes in any size range. A well-graded
soil has a Cu value of 5 or more.
From the result of sieving analysis carried out, both the silica sand and river
sand is 100 percent felt within the range of passing 0.600 mm test sieve and retained
on 0.063 mm test sieve. Therefore it is permitted to use for field density test.
48
From the result of sieving analysis test including hydrometer test of the soil
sample, the clay contains about 22 percent, silt is around 5 percent and sand is about
20 percent. Thus, the soil can be classified as reddish sandy silty Clay.
Table 4.3: River sand And Silica Sand Coefficiency
River Sand
Silica Sand
Cu = 1.58
Cu =1.43
Cc =1.16
Cc =1.03
% Of Passing
Silica Sand Sieve Analysis
100
90
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
10
Particle Size
Figure 4.1: Silica Sand Grading Curve Result
River Sand Sieve Analysis
100
90
% Of Passing
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
Particle Size
1
10
49
Figure 4.2: River Sand Grading Curve Result
Reddish silty CLAY Sieve Analysis
100
90
% Of Passing
80
70
60
50
40
30
20
10
0
0.0001
0.001
0.01
0.1
1
10
Particle Size
Figure 4.3: Filled Material Grading Curve Result
4.3
Laboratory Compaction Test
The process of mechanically pressing together the particles of a soil to
increase the density is extensively employed in the construction of embankments
and in strengthening the subgrade of roads and runways. Compaction is the
packing together of soil particles by the expulsion of air. The densities achieved by
compaction are invariably expressed as dry densities, generally in Mg/m3.
50
The procedure forms the basis of the British Standard compaction and used
a compact effort in which roughly corresponded to that available in the field at the
time. Laboratory tests are useful for the classification and the selection of fill
materials for earthworks, but it is not usually possible to apply results from these
tests to work in the field due to the difference in the compactness efforts. For large
earth full scale tests
should be carried out, compacting a test section with the actual plant that will
ultimately be employed on the project. In this way it is possible to determine the
number of passes of the machine required in achieving the desired dry density. The
maximum dry density depends upon the type of soil compacted.
The soil being used for filling at the selected site is classified as reddish silty
clay. There was one laboratory compaction test carried out to the filled material to
determine the maximum dry density and the optimum moisture content. After the
laboratory compaction test, the maximum dry density is 1.400 Mg/m3 as obtained
from the moisture content against dry density relation curve. The optimum
moisture content is about 27 percent. This is meant that the soil that is used for site
filling will be able to achieve in-situ field density of 1.400 Mg/m3 provided that the
number of passes of the selected machine is determined.
From the field density tests result collected, the compactive efforts were
about 75 percent to 98 percent. However, there is a possibility of over-compaction
in the field if the compact effort does not take the soil into the range beyond
optimum moisture content.
1.410
15% Air void Line
10 % Air Void Line
1.405
DRY DENSITY (Mg/m 3)
1.400
1.395
1.390
1.385
1.380
1.375
51
Figure 4.4: Filled Material Laboratory Compaction Curve Result
4.4
In-situ Field Density Test
The analysis is done at the selected site. The site was compacted using a 5
ton roller. With different number of passes to the selected ground, sand
replacement test was carried out. Each time there were five tests done within the
selected location of approximately 1 square meter. Two tests were done using
standard sand or ‘silica sand’ and three tests were using river sand. The average of
the field density was taken for the two tests of silica sand and the same to the 3 tests
of the river sand. The studied was done with about 12 different compactness of the
ground. Therefore there were about 20 silica sand tests result of in-situ field density
using sand replacement method and 30 tests result using river sand. Then the final
result will be able to produce 12 points of different in degree of compaction for
silica sand and river sand and the related density can be obtained.
4.4.1
Summary Of Field Density Test Result
The table below shows the calculated average dry density of the silica sand
and river sand conducted in-situ at different level of compaction at the selected site.
52
Table 4.4A: Summary In-situ Field Density Test
Result Set 1
FD
SILICA
AVERAGE
REFERENCE SAND
SILICA
1
1.268
2
1.279
RIVER AVERAGE
SAND
RIVER
SAND
1.274
3
1.289
4
1.298
5
1.297
Table 4.4B: Summary In-situ Field Density Test
Result Set 2
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
8
1.276
9
1.270
RIVER AVERAGE
SAND
RIVER
SAND
1.273
10
1.295
11
1.306
12
1.297
Table 4.4C: Summary In-situ Field Density Test
Result Set 3
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
13
1.294
14
1.310
1.295
1.299
RIVER AVERAGE
SAND
RIVER
SAND
1.302
15
1.331
16
1.330
17
1.328
1.330
53
Table 4.4D: Summary In-situ Field Density Test
Result set 4
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
21
1.310
22
1.319
RIVER AVERAGE
SAND
RIVER
SAND
1.315
18
1.335
19
1.353
20
1.343
Table 4.4E: Summary In-situ Field Density Test
Result Set 5
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
26
1.295
27
1.295
RIVER AVERAGE
SAND
RIVER
SAND
1.295
23
1.313
24
1.317
25
1.328
Table 4.4F: Summary In-situ Field Density Test
Result Set 6
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
31
1.255
32
1.243
1.344
1.319
RIVER AVERAGE
SAND
RIVER
SAND
1.249
28
1.280
29
1.266
30
1.273
1.273
54
Table 4.4G: Summary In-situ Field Density Test
Result Set 7
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
36
1.098
37
1.092
RIVER AVERAGE
SAND
RIVER
SAND
1.095
33
1.118
34
1.121
35
1.104
1.114
Table 4.4H: Summary In-situ Field Density Test
Result Set 8
FD
SILICA AVERAGE
SILICA RIVER AVERAGE
REFERENCE
SAND
SAND
RIVER
SAND
38
1.129
39
1.116
1.123
40
1.139
41
1.143
42
1.146
1.143
Table 4.4I: Summary In-situ Field Density Test
Result Set 9
FD
SILICA AVERAGE
SILICA RIVER AVERAGE
REFERENCE
SAND
SAND
RIVER
SAND
43
1.126
44
45
1.130
1.128
1.139
55
46
1.147
47
1.158
Table 4.4J: Summary In-situ Field Density Test
Result Set 10
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
48
1.100
49
1.112
1.148
RIVER AVERAGE
SAND
RIVER
SAND
1.106
50
1.130
51
1.127
52
1.118
1.125
Table 4.4K: Summary In-situ Field Density Test
Result Set 11
FD
SILICA AVERAGE
SILICA RIVER AVERAGE
REFERENCE
SAND
SAND
RIVER
SAND
53
1.209
54
1.208
1.209
55
1.236
56
1.232
57
1.235
Table 4.4L: Summary In-situ Field Density Test
Result Set 12
FD
SILICA
AVERAGE
REFERENCE
SAND
SILICA
58
1.251
1.234
RIVER AVERAGE
SAND
RIVER
SAND
56
59
1.239
1.245
60
1.275
61
1.259
62
1.270
1.268
4.4.1.1 Tabulated Dry Density
Table 4.5: Summary Result of the Field Density Test
AVERAGE DRY
DENSITY RIVER
SAND(Mg/m3)
AVERAGE DRY
DENSITY SILICA
SAND(Mg/m3)
1.295
1.274
1.299
1.273
1.330
1.302
1.344
1.315
1.319
1.295
1.273
1.249
1.114
1.095
1.143
1.123
57
1.148
1.128
1.125
1.106
1.234
1.209
1.268
1.245
4.4.1.2 Dry Density Relationship Between Silica Sand And River Sand
Figure 4.4 below is the outcome of the analysis. The relationship between
silica sand dry density and the river sand dry density is established. The correlation
factor is 0.9813.
58
Silica Sand Dry Density
Dry Density Correlation Between River
Sand And Silica Sand
1.350
1.300
y = 0.9813x
R2 = 0.9993
1.250
1.200
1.150
1.100
1.050
1.000
1.000
1.050
1.100
1.150
1.200
1.250
1.300
1.350
River Sand Dry Density
Figure 4.5 : River Sand and Silica Sand Relationship Graph
1.400