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International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 02, February 2019, pp. 836-853, Article ID: IJCIET_10_02_081
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=02
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
MINERALOGICAL EVALUATION OF
LATERITIC SOIL OF SELECTED ZONES IN
UDUPI DISTRICT, KARNATAKA, INDIA
Bhagyashree
Assistant Professor, Department of Civil Engineering, MIT, MAHE, Manipal
Udayashankar H N
Professor, Department of Civil Engineering, MIT, MAHE, Manipal
Purushotham Sarvade
Professor, Department of Civil Engineering, MIT, MAHE, Manipal
ABSTRACT
Lateritic soil is one of the main soil types in the tropical countries like India for
basic construction works. Since lateritic soils are the main underlying soil structure
in coastal Karnataka, its detailed study of mineralogical properties is of utmost
importance. The study area chosen is Udupi district and samples were procured from
coastal plains and hinterland regions. The samples taken from each places (three
layers-top, middle and bottom at around 2.5-3 m depth) were collected in zip locked
polythene bags and were oven dried at 1050 Celsius for 24 hours and then passed
through 75 µm IS sieve size. For clear images of the soil structure and for
identification of elements, samples were coated with gold sputtering. These samples
were tested by Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray
Spectroscopy (EDAX/EDS) and analyzed. SEM results show various minerals present
in the samples. EDAX results show the percentage of each element (like C, O, Si, K,
Cu, Ti, Mg etc) present in the sample. Therefore it can be concluded that laterites
change their composition from iron to aluminium resulting in bauxite ore as one
moves towards north in the coastal belt of Karnataka.
Keywords: EDAX, Laterite soil, Mineralogy, SEM, Sputtering.
Cite this Article: Bhagyashree, Udayashankar H N and Purushotham Sarvade,
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District,
Karnataka, India, International Journal of Civil Engineering and Technology, 10(2),
2019, pp. 836-853.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=02
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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1. INTRODUCTION
The word “laterite” is procured from a Latin language from the phrase ‘later’, which means a
brick. It is a red colored material, which is rich in iron content that originates mostly in South
India. The basic character of the lateritic clay soils allows them to absorb water easily into
their inter-granular pore spaces. Due to their inherent nature of poor permeability, they
prevent them from discharging the excess water held in the pore-spaces [1]. Coastal area of
Karnataka, which includes three districts namely Dakshina Kannada, Udupi and Uttara
Kannada, is an area, which is highly stressed due to lots of developmental activities taking
place. It is very crucial activity center of Karnataka owing to its location.
The SEM is routinely used to generate high-resolution images of shapes of objects and to
show spatial variations in chemical compositions: 1) acquiring elemental maps or spot
chemical analyses using EDS, 2)discrimination of phases based on mean atomic number
(commonly related to relative density) using BSE, and 3) compositional maps based on
differences in trace element "activator’s" (typically transition metal and Rare Earth elements).
The SEM is also widely used to identify phases based on qualitative chemical analysis and/or
crystalline structure. Precise measurement of very small features and objects down to 50 nm
in size is also accomplished using the SEM [2][3]. Energy-dispersive X-ray spectroscopy
(EDS, EDAX), is an analytical technique used for the elemental analysis or chemical
characterization of a sample. It relies on an interaction of some source of X-ray excitation and
a sample. Its characterization capabilities are due in large part to the fundamental principle
that each element has a unique atomic structure allowing a unique set of peaks on its
electromagnetic emission spectrum (which is the main principle of spectroscopy)[4][5].
Mineral content can be considered as the crucial feature that controls the shape, size, and
various characteristics. Fine particle percentage (particles passing IS sieve size of 75 µm) will
have very important efficacy related to rendering the soil to be used as underlying foundation
material. More amounts of finer particles may lead to the depletion of possible highest
density and bearing capacity of the soil which in-turn leads to enhancement in the
vulnerability to immobilization due to infiltration of water [6]. The metals present in the
lateritic soils are crystalline oxides of Fe and their residues, which will be altered towards
interchangeable structure on the top layer of the soil. Special absorbing capability is observed
in the minerals towards few heavy metals, thus they exert a straight impact on geochemistry
and reversible nature of heavy metals in the lateritic soils [7].
Changes in size and shape of clay soils can be observed owing to changes in water
content that will lead to damages to structures erected on them. In lots of research works, it
has been strived to describe the couplings owing to moisture variations and its succeeding
volume change alterations. Research related to the durability of the clay soils unmasked to
external atmospheric pressures like alternate dry and wet cyclic variations need to be found
out. [8].
The other type of soil found in coastal Karnataka and along the Konkan belt is
Lithomargic clay. Whenever the top laterite soil (2.5-3 m thick) is removed, the underlying
shedi soil gets exposed. Construction activities are done very often on this exposed shedi soil
or in many cases, construction activities are done on lateritic soil filled-up grounds. Such
shedi ground will have very low bearing capacities. Such grounds need to be improved to
achieve higher bearing capacities. [9].
2. METHODOLOGY
For any research work, it is necessary to clearly define the fieldwork so as to get intended
opportune results. Hence, it is imperative to regulate the position of each sampling location.
Bhagyashree, Udayashankar H N and Purushotham Sarvade
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Each sampling location should provide a distinct representative result with good number of
samples and minimize errors. The samples will be collected from the lateritic mesa which are
situated right after the coastal plains which are usually constituted by flat hilltops. This region
is rich in lateritic soil and this lateritic soil is stressed due to various infrastructural
development taking place on this soil. Lateritic quarries are also situated in these places.
Some samples are collected from hinterland consisting of rolling topography which contains
small plateaus that contains lateritic soil in high concentrations. 10 sampling locations are
selected from the coastal plains and hinterlands (where lateritic profile is exposed).
2.1. Sample Collection and Preparation
For mineralogical test, the samples taken from each places (three layers-top, middle and
bottom at around 2.5-3m height) were collected in zip locked polythene bags and were oven
dried at 1050 Celsius for 24 hours and then passed through 75 µm IS sieve size. Sputter
coverings done for the specimen with a thin layer of conducting material, typically a metal,
such as a gold (Au) alloy. It helps in providing deposition of a thin-film on the samples. This
will help in samples to be more conductive in the present study (coating of gold sputtering is
provided on the soil samples). Then it will undergo SEM/EDS analysis
3. RESULTS
The images of Scanning Electron Microscope and EDAX results are discussed below in the
form of images and tables. In the figures, (a) represents top layer, (b) represents middle layer
and (c) represents bottom layer of soil respectively. In section 3.1, the images show various
minerals present in lateritic soil and in section 3.2 EDAX results show percentage variation
of weights of different elements present in lateritic soil.
3.1. SEM Images of Udupi Region
Figure 1 Scanning electron micrographs of Kapu (a) magnetite (b) arrows points towards Diaspora
(c) Clay is pointed using arrows and hematite grains in the oval shape.
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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Figure 2 Scanning electron micrographs of Katapadi(a) Hematite, (b) and (c) oval shape represents
aluminum, box represents ferro-nickel particles and arrow showing quartz in the second and third
layer of Katpadi.
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Figure 3 Scanning electron micrographs of Jantra (a) White oval shapes represents silica and white
arrows represent magnetite spicules and yellow arrows show clay particles (b) Iron particles are
showed in oval shape (c) Nickel is showed in oval shape
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Figure 4 Scanning electron micrographs of Kolalagiri (a) nickel (b) Aluminum (c) clay
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Figure 5 Scanning electron micrographs of Shirva (a) Oval shape showing aluminum particles and
arrow representing iron contents (b) Arrows shows hematite particles (c) goethite
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Figure 6 Scanning electron micrographs of Ucchila (a) magnetic spicules (b) quartz contents and (c)
nickel
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Figure 7 Scanning electron micrographs of Udupi (a)aluminum (b)arrow showing quartz and oval
shape indicating clay (c) the circle is representing trigonal hematite grains.
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Figure 8 Scanning electron micrographs of Hejamadi (a) Iron is marked in oval shape and arrows
represents clay content (b) Gibbsite and arrows show diaspora (c) Trigonal structures of hematite is
seen
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Figure 9 Scanning electron micrographs of Manipal (a) The Right Arrow represent the Hematite,
Diamond shape represents the Magnetite Stipules, Box represent the Al in top Profile.(b) Box
represent the Al, Right Arrow represent the Hematite in Middle Profile. (c) Diamond shape represents
the Magnetite Stipules, Box shape represents Aluminum, arrow represent the Hematite.
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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Figure 10 Scanning electron micrographs of Palli (a) The Yellow Arrow represent the silica, White
Arrow represent the Hematite, Box shape represents Aluminium.(B) White Arrow represent the silica,
Box represent the Aluminium (C) Yellow Arrow represent the Hematite, Box shape represents
Aluminum.
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3.2. EDAX Results
Table 1 Percentage weights of elements present in top layers of soil
PLACES/% WEIGHTS
KOLALAGIRI UDUPI KATPADI KAPU SHIRVA UCHILA JANTRA HEJMADI MANIPAL PALLI
C 21.2 7.63 27.49 26.44 34.49 15.75 14.55 9.08 7.72 8.07
O 43.31 55.63 44.59 43.63 53.28 42.61 42.85 56.69 42.34 47.66
Al 9.25 12.93 8.47 9.53 12.32 10.73 10.35 14.59 13.7 14.4
Si 13.16 12.86 8.63 7.93 13.36 13.36 10.53 15.32 10.32 13.03
Fe 11.41 9.71 5.72 6.33
12.57
3.04 12.65 10.78
Ti 0 0.59 0.39
2.97
Cr 0
0.85 2.8 12.58
K 0 0.65 0.49
Mg 0
0.21
Mn 0
14.07 17.74
Ni 0
0.023 0.22
Figure 11 Figure 12
Figure 13 Figure 14
Figure 15 Figure 16
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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Figure 17 Figure 18
Figure 19
Table 2 Percentage weights of elements present in middle layers of soil
PLACES/ WEIGHTS
KOLALAGIRI UDUPI KATPADI KAPU SHIRVA UCHILA JANTRA HEJMADI MANIPAL PALLI
C 10.85 7.41 18.73 28.22 21.82 26.06 19.65 16.17 14.49
O 37.82 56.95 45.87 48.53 45.25 53.74 41.14 51.75 49.41 51.93
Al 11.62 14.54 10.47 9.3 12.02 14.08 19.67 11.13 14.76 18.84
Si 18.16 15.07 10.74 6.41 13.11 15.98 20.13 12.41 12.51 16.02
Fe 0 4.98 8.84 4.11
8.18 14.03 10.79
Ti 0 0.69 0.75 0.465
Cr 0
5.73 26.69
K 0 0.5
0.34
0.51
Mg 0
Nb 31.53
3.9
9.79
Mn 0
14.07 20.45
Ni 0
0.95 1.35
Figure 20 Figure 21
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Figure 22 Figure 23
Figure 24 Figure 25
Figure 26 Figure 27
Figure 28
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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Table 3 Percentage weights of elements present in bottom layers of soil
PLACES/% WEIGHTS
KOLALAGIRI UDUPI KATPADI KAPU SHIRVA UCHILA JANTRA HEJMADI MANIPAL PALLI
C 19.73 9.27 16.48 31.04 8.25 18.75 9.45 15.22
O 44.72 50.77 44.9 42.51 46.12 50.03 41.04 52.47 46.08 43.51
Al 12.19 14.99 10.54 8.57 13.2 11.87 9.51 14.05 14.46 13.92
Si 13.77 15.29 9.83 5.62 13.31 13.98 9.69 14.06 14.34 13.52
Fe
9.18 11.11 6.78
25.21 3.03 5.74 3.67
Ti
0.65 0.8 0.39
0.72
Cr
1.215 13.18
K
0.73 0.5 0.36
Nb
2.78
Mn
18.25 14.88
Ni
0.09 0.655
Figure 29 Figure 30
Figure 31 Figure 32
Figure 33 Figure 34
Bhagyashree, Udayashankar H N and Purushotham Sarvade
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Figure 35 Figure 36
Figure 37
5. CONCLUSION
According to the results obtained from SEM-EDAX analysis the following inferences can be
made. The elements such as Aluminum, Silica, and Carbon are predominately are found in all
the 10 places. Except Shriva and Jantra, iron content was seen in 8 places. Nb was absent in
Top layer soil whereas present in bottom, middle layers and found in 3 places only.
Magnesium is absent in middle layer and bottom layers. The samples collected from Kapu
was rich in Carbon and poor in Fe, Al, Si, Ti and K. High content of Mn, Ni, Cr and Al was
found in Palli. Samples collected from Udupi contained high Percentage of K, Si, Al and Low
Percentage of C. Then from Hejamadi, high percentage of elements like Al, Si, K and Low
percentage of Fe and Cr were found.
Therefore it can be concluded that the lateritic soil in Udupi district is rich in aluminium
and silica and the next predominant element being iron. Hence it can be seen that as one
moves from south to north in the coastal belt of Karnataka laterites change their composition
from iron to aluminium resulting in bauxite ore. Their chemistry is controlled by the
weathering of sedimentary rocks.
5.1. Future Scope
XRD analyses can be done for all these samples so that mineral composition can be
found out
Geotechnical tests can be carried out for assessing engineering properties of the soil
samples
Tests can be carried out on laterite blocks to know their strength to be used as
building materials
Mineralogical Evaluation of Lateritic Soil of Selected Zones in Udupi District, Karnataka, India
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ACKNOWLEDGEMENTS
Department of Civil Engineering is thanked for laboratory facilities, Vishwas K and
Kavyashree is thanked for helping in sample collection.
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