EFFECTS OF USED MOTOR OIL ON THE ENGINEERING PROPERTIES OF
LATERITIC AND CLAYEY SAND MATERIALS IN NIKE, ENUGU EAST L.G.A.,
ENUGU STATE, NIGERIA.
A PROJECT SUMMITTED TO THE DEPARTMENT OF GEOLOGY, FACULTY OF
PHYSICAL SCIENCES, UNIVERSITY OF NIGERIA,NSUKKA, IN PARTIAL
FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF
SCIENCE
BY
AKAGHA, FRANKLIN UCHECHUKWU
PG/M.SC/10/52920
NOVEMBER, 2014
i
TITLE PAGE
EFFECTS OF USED MOTOR OIL ON THE ENGINEERING PROPERTIES OF
LATERITIC AND CLAYEY SAND MATERIALS IN NIKE, ENUGU EAST L.G.A.,
ENUGU STATE, NIGERIA.
ii
CERTIFICATION
The work embodied in this project is original and has not been submitted in full or part for any
other degree or professional qualification for this or any other university.
AKAGHA, FRANKLIN UCHECHUKWU
PG/M.SC/10/52920
iii
APPROVAL PAGE
MrAkagha, Franklin Uchechukwu, a post graduate student of Department of Geology has
satisfactorily completed the requirements in research work for the degree of Masters of Science
(M.Sc.) in Geology with option in Engineering Geology
-------------------------------------------DrIgweOgbonnaya
(Supervisor)
----------------------------------------------Prof. O. P. Umeji
(Head of Department)
iv
DEDICATION
This work is dedicated to God Almighty for his mercies and love in my life.
v
ACKNOWLEDGEMENTS
I wish to express my profound gratitude to my supervisor, DrIgweOgbonnayafor making this
research work a reality, I also want to appreciate
MrUna, Chuku O. and lecturers in the
department of Geology University of Nigeria, Nsukka for the part they played in making this
work a success.
I will not fail to acknowledge my parents and family members for their support and prayers
during this period.
Finally, I thank the Almighty God for His favour, health and everything He has done for me.
vi
ABSTRACT
Used motor oil is constantly disposed indiscriminately at mechanic workshops in Nigeria
without considering its impact to the soil and the environment at large. This work investigates
intrinsic changes in the engineering properties of lateritic and clayey sand materials. Soil samples
were collected at the depth of 30cm and were then air dried at room temperature for seventy two
(72) hours. After air drying, the lateritic material was divided into five equal parts. Each of the
samples was artificially contaminated with 4%, 6%, 8%, and 10% of used motor oil; the last
uncontaminated portion was used as the control sample. This same procedure was carried out on
the clayey sand material. These materials were kept in an air tight polythene bag for fourteen
(14) days to enable the mixture to cure. Samples were subjected to mechanical analysis, specific
gravity, permeability, Atterberg limits, compaction and triaxial tests. Results revealed that
specific gravity of the samples decreased with increase in used motor oil from 2.66 – 2.25 in
lateritic soil and 2.72 – 2.35 in clayey sandy soil, permeability also decreased with increase in
the percentage of used motor oil, 2.75 – 1.85 cm/sec in lateritic soil and 1.97 – 1.70 cm/secin
clayey sandy soil, maximum dry density(MDD) and shear strength of the samples also decreased
with increased percentage of used motor oil in both the lateritic and clayey sand samples. This
research shows that used motor oil reduces the shear strength of the soil.
vii
TABLE OF CONTENTS
Title Page ……………………………………………………………………………
i
Certification ………………………………………………………………………....
iii
Approval …………………………………………………………………………… ..
iv
Dedication……………………………………………………………………………
v
Acknowledgements…………………………………………………………………..
vi
Abstract………………………………………………………………………………
vii
Table of Contents……………………………………………………………………
viii
List of Figures………………………………………………………………………..
x
List of Table…………………………………………………………………………
xii
CHAPTER ONE: INTRODUCTION………………………………………………
1
1.1
1
Preamble………………………………………………………………………
1.2Aims and Objectives …...……………………………………………………
4
1.3 Literature Review …………………………………………………………………
4
CHAPTER TWO: DESCRIPTION OF THE STUDY AREA………………..
7
2.1 Location of the Study Area…………………………………………………
7
2.2Climate of the Study Area …………………………………………………….
9
2.3Geology of the Study Area ……………………………………………………… 9
CHAPTER THREE: RESEARCH METHODOLOGY……………………………
13
3.1 Sample Preparation ………………………………………………………………..
13
3.2 Laboratory Tests ……………………………………………………………………
13
3.2.1 Mechanical Analysis …………………………………………………….
14
3.2.2 Specific Gravity ……………………………………………………….
15
viii
3.2.3 Permeability …………………………………………………………….
16
3.2.4 AtterbergLimits ………………………………………………………
16
3.2.5 Compaction Test ………………………………………………………
18
3.2.6 Triaxial Test ……………………………………………………………
18
CHAPTER FOUR: RESULTS AND DISCUSSION……………………………… ..
20
4.1 Mechanical Analysis …………………………………………………………….
20
4.2 Specific Gravity …………………………………………………………………
20
4.3 Permeability ………………………………………………………………………
24
4.4 Atterberg Limits …………………………………………………………………
24
4.5 Compaction Test …………………………………………………………………
25
4.6 Triaxial Test ………………………………………………………………………
29
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS………………
36
5.1 Conclusions………………………………………………………………………
36
5.2 Recommendations………………………………………………………………
37
References………………………………………………………………………………
38
ix
LIST OF FIGURES
Figure 1: Used Motor Oil carelessly disposed at the mechanic workshop …………… ..
3
Figure 2: Location Map of Study Area. …………………………………………………
8
Figure 3: Geological map of southeastern Nigeria (modified from Akande et al, 2007) … 11
Figure 4: Geologic map of Enugu and its environs (Onunkwo-Akunne et al., 2012) …… 12
Figure 5: Distribution curve for the lateritic material …………………………………...
22
Figure 6: Distribution curve for the Clayey sand material ……………………………..
23
Figure 7: Compaction curves of the contaminated lateritic soil as compared
to the uncontaminated …………………………………………………………
27
Figure 8: Compaction curves of the contaminated clayey sand material as
compared to the uncontaminated ………………………………………………
28
Figure 9: Triaxial test for the uncontaminated lateritic material ………………………… 31
Figure 10: Triaxial test for the uncontaminated clayey sand material …………………
31
Figure 11: Triaxial test for the 4% oil contaminated lateritic material…………………
32
Figure 12: Triaxial test for the 4% oil contaminated clayey sand material ……………… 32
Figure 13: Triaxial test for the 6% oil contaminated lateritic material …………………
33
Figure 14: Triaxial test for the 6% oil contaminated clayey sand material ……………… 33
Figure15: Triaxial test for the 8% oil contaminated lateritic material …………………
34
Figure 16: Triaxial test for the 8% oil contaminated clayey sand material …………….
34
Figure 17: Triaxial test for the 10% oil contaminated lateritic material ……………….
35
Figure 18: Triaxial test for the 10% oil contaminated clayey sand material …………...
35
x
LIST OF TABLE
Table 1: Summary of test results……………………………………………………….. 21
xi
CHAPTER ONE
INTRODUCTION
1.1 PREAMBLE
Engine oil or motor oil is derived from petroleum based compounds which consists
mainly of hydrogen and carbon. Thus, engine oil is a hydrocarbon compound. Used motor oil
can be dispersed into the soil in four different ways: escape and loss of oil during motor
operations; applications on rural roads for dust control, during asphalting with asphalt-containing
waste crankcase oil, and finally, when it is placed directly on landfills or at the mechanic
workshops. The release of used engine oil on soil poses a big threat to engineering structures.
Apart from engineering structures, soil microbes and plants as well as contaminate groundwater
resources for drinking or agriculture may also be contaminated (Hong et al, 2010). Used motor
oil is a very dangerous polluting product, it contains polynuclear aromatic hydrocarbons (PAH’s)
and high levels of heavy metals, PAH’s are dangerous to health because some are known to be
mutagenic
and
carcinogenic,
benzo[a]pyrene
are
well
known
for
their
high
carcinogenicity(IRAC, 1983; Raphael 1989).
Used motor oil contaminations of soil are common wherever motor mechanic workshops
are located. It has been reported that the bearing capacity of such soils is drastically reduced and
made engineering structures unsuitable to run, or plant growth by reducing the availability of
nutrients or by increasing toxic contents in the soil (Euchun and Braja, 2001). Mechanic
workshops are seen at every point in town and developing areas (Fig. 1); some well-known
mechanics have occupied a piece of land for more than 10 years. The oil from vehicles are
disposed carelessly, sometimes the oil is drained from the vehicle and collected in a container
xii
and are disposed at a particular point on the land but most times released directly from the
vehicle to the ground. Cases have been witnessed where individuals or even the government
reclaims a piece of land that was formally used as a mechanic workshop and structures are
erected on it.
The essence of this research is to examine the influence of used engine oil on the engineering
properties of lateritic and clayey sand materials.
Hydrocarbon contamination will not just affect the quality of the soil but will also alter the
physical properties of oil contaminated soil. This will lead to geotechnical problems related to
construction or foundation structure on this oil contaminated sites (Mackenzie, 1970). This
implies that care should be taken in the disposal of hydrocarbon compounds. But unfortunately,
an average Nigerian do not care how the bad oil from his vehicle is being disposed, all he cares is
that the oil has been drained from his vehicle to prevent damage to it (vehicle).
xiii
Fig. 1: Used Motor Oil carelessly disposed at the mechanic workshop
xiv
1.2 AIM AND OBJECTIVES OF THIS STUDY
This study will aim at;

Investigating the effects of the used engine oil on the engineering properties of the
lateritic and clayey sand soil material and

Make suggestions on how to manage the effects of used engine oil if an engineering
structure will be erected in a place that is already contaminated.
1.3 LITERATURE REVIEW
Different researchers have investigated on a similar topic; some of their findings have been
reviewed for better understanding of this topic. Evgin and Das (1992) carried out triaxial test on
contaminated and uncontaminated clean sand and they found that the shear strength of the
contaminated sand drastically reduced.
Vijay (2000) and Sanjay et al (2002) have also conducted tests to determine the geotechnical
properties of oil contaminated sands and the test results indicated that the compaction
characteristics are influenced by oil contamination. The angle of internal friction of the sand
based on total stress condition was found to decrease with the presence of oil in the pore spaces.
Odjegba and Sadiq (2002), reported that large amounts of used engine oil are liberated into the
environment when motor oil is changed and disposed into gutters, water drains, open vacant
plots and farmlands, a common practice in Nigerian mechanic workshop. This used engine oil
has negative effect on the environment.
The engineering properties of oil contaminated sand were also investigated by Mashalal et al.
(2007) who reported decreasing values of strength, permeability, maximum dry density,
optimum water content and Atterberg limits properties with increases in oil contents.
xv
Rehman et al (2007) and Mohammad and Shahaboddin (2008) concluded that the compression
behavior of montmorillonite indicated that the particles tend to coagulate and to behave like
granular materials in the presence of organic contaminants.
Achuba and Peretiemo-Clarke, (2008) observed that used engine oil, when present in the soil,
creates an unsatisfactory condition for life in the soil, which is due to the poor aeration it causes
in the soil, immobilization of soil nutrients and lowering of soil pH.
To investigate the behavior of oil contaminated sand under foundation footings, Ahmed Nasir
(2009) conducted experimental and theoretical studies of strip footings on oil contaminated sand
and found that load settlement behaviour and ultimate bearing capacity of the footing can be
drastically reduced by the contamination. The bearing capacity decreased and the settlement of
the footing increased with increasing depth and length of the contaminated sand layer.
Murat and Yildiz (2010) reported that Liquid limit and consolidation parameters of highly plastic
clay tend to decrease while shear strength parameters increase in the presence of organic
contaminants.
Rahman et al (2010) found that the presence of engine oil in granitic soil lowered the values of
the Atterberg limit. Also the maximum dry density and the optimum moisture content dropped
due to increase in the presence of the engine oil.
Ashraf (2011) studied the effects of oil contamination on over consolidated clay and reported
decrease in the Atterberg limits, unconfined compressive strength but increases in the
permeability and compression and swell potential of the contaminated soil. Furthermore the oil
contamination led to close parking of the clay particles.
Nazir A.K (2011) carried out a test on the effect of motor oil contamination on the geotechnical
properties of over consolidated clay over a period of time. In his study, he found that both liquid
xvi
and plastic limits decreased with the increase of time duration of up to 3 months but the stress
history of the clay was not affected by the contamination.
Rahman and Hamzah (2011) in a similar research found that the unconfined undrained triaxial
test carried out on basaltic residual soil contaminated with engine oil showed the decrease of the
shear strength as the oil content is increased.
Used engine oil also renders the environment unsightly and constitutes a potential threat to
humans, animals, and vegetation. As the usage of petroleum hydrocarbon products increase, soil
contamination with diesel and engine oils is becoming one of the major environmental problems
(Ameh et al., 2012).
Oluwapelumi and Omotayo (2012) observed that petroleum hydrocarbon contamination will not
just affect the quality of the soil but will also alter the physical properties of oil contaminated
soils. This will lead to geotechnical and foundation problems related to construction of buildings
and other Civil Engineering structures such roads, dams, water/oil retaining structures.
Ijimdiya (2013) observed that the presence of oil in the lateritic soil led to the reduction in the
values of UCS, void ratios and the increase in the values of volume compressibility, Mv, and
coefficients of consolidation, cv. Based on findings of previous works as reported above, it
clearly revealed that oil contamination has negative influence on the geotechnical properties of
soils. Therefore, before engineering structures will be erected on areas that have been
contaminated by used engine oil, the area require some remediation in order to improve the
engineering properties of the affected soil.
xvii
CHAPTER TWO
DESCRIPTION OF THE STUDY AREA
2.0 STUDY AREA
2.1 LOCATION
The study area is located at Nike in Enugu East L.G.A in Enugu state. It lies within
latitudes 6o22 and 6o28 North of the equator and longitudes 7o29 and 7o30 East of Greenwich
meridian. Two soil samples were collected at two different communities within Nike. The
lateritic soil material was collected at Ugwuji town, while the clayey sand material was collected
at Ibagwa town (Fig. 2). The communities are part of the developing areas of Enugu State. Few
residential houses can be seen sprouting around the area, most of them uncompleted.
Nike is accessible with lots of tarred and untarred roads that were of great advantage in
the course of this work. The main access routes include Enugu - Abakpa road and Opi – Nike
road.
xviii
Fig. 2: Location Map of Study Area.
xix
2.2 CLIMATE OF THE STUDY AREA
The study area has a tropical climate with two distinct seasons. It has two distinct
seasons, the rainy and dry. The rainy season begins from April and ends October, while the dry
season begins in November and ends in March. Records of rainfall showed high values within
the months of May to early August when there is a rainfall break and resumes in late August to
end of October with higher values. There is virtually little or no rainfall from November to
March. Average annual rainfall is between 1875mm and 2500mm and the pressure range is
from 1010 to 1012.9 millibars. The mean monthly temperatures vary from 22oC to 28oC in the
wet season and between 28oC and 32oC in the dry season For the whole of Enugu State the
mean daily temperature is 26.7 °C (80.1 °F). Other weather conditions affecting the city
include Harmattan, a dusty trade wind lasting a few weeks of December and January. Like the
rest of Nigeria, Enugu is hot all year round. The study area lies between the tropical rainforests
which dominate nearly half of southern Nigeria and is characterised by luxuriant vegetation
and abundant plant species. It is bounded by fresh water swamp forest in the south and Guinea
Savanna in the North. The vegetation is marked by continuous growth of trees, shrubs and
climbing plants (Moanu and Inyang, 1975; Igwe et. al, 2012).
2.3 GEOLOGY OF THE STUDY AREA
Nike is part of the Campanian to Eocene Anambra basin formed as a result of the
structural inversion and folding of the Aptian-Santonian Abakaliki basin (Benkhelil, 1989;
Kogbe, 1989; Ojoh, 1992; Obi and Okogbue, 2004). The filling of the Anambra basin is
generally accepted to have taken place during three depositional cycles. From the late
xx
Campanian to the early Maastrichtian (The Nkporo group) from early Maastrichtian to the late
Maastrichtian (The Mamu, Ajali, Nsukka series) and from late Maastrichtian to Eocene (Imo–
Ameki series) (Petters, 1978). The Nkporo group comprising a basal marine Nkporo shale,
(which rest unconformably upon the pre-Campanian strata the Abakaliki basin) the shallowing
upward sandy Owelli Formation, and the Enugu shale, which consist of bluish dark grey shales
containing abundant carbonaceous matter with thin siltsone and sandstone layers. The Nkporo
group is overlain by Mamu Formation which consists of heteroliths of siltstone, shale and fine
grained sands with coal seams. Ajali Formation was deposited after the Mamu Formation and
consists of Unconsolidated to poorly cemented sandstone that exhibit profuse cross-breeding
mainly tidal deposits with a virtual absence of clay. (Reyment, 1965; Ladipo, 1986; Obi, 2000).
Mamu and Ajali Formations are the two main geologic Formations that outcropped in the study
area (Figs. 3 and 4).
The Ajali formation is overlain by the Maastritchian to Palaeocene Nsukka formation
which consist of sandstone, dark shale/sandy shale with thin coal seams and the Paleocene to
Eocence Imo shale Formation which consists of dark grey Fossiliferous marine shales with sand
stone and pebbly sands, and ironstone. In the Eocene another structural inversion uplifted and
slightly tilted the Anambra basin while shifting the depositional centre further south to the Niger
Delta basin (Obi et al 2001).
xxi
Fig. 3: Geological map of southeastern Nigeria (modified from Akande et al, 2007)
xxii
Fig. 4: Geologic map of Enugu and its environs (Onunkwo-Akunne et al., 2012)
xxiii
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 Sample preparation
Two samples were collected for this study. One is a lateritic material and the other is a clayey
sand material. These materials were collected at the depth of 30cm. the samples were then air
dried at room temperature for 72hrs.
After air drying, the lateritic material was divided into five equal parts. Each of the samples
was artificially contaminated with 4%, 6%, 8%, and 10% of used motor oil; the last
uncontaminated portion was used as the control sample. This same procedure was carried out on
the clayey sand material with the same percentages of used motor oil as contaminants and an
uncontaminated sample used as the control. These materials were kept in an air tight polythene
bag for 14 days to enable the mixture to cure.
3.2 Laboratory tests
The laboratory tests carried out on the materials are mechanical analysis, specific gravity,
permeability, Atterberg limits, compaction test and triaxial test.
Each of these tests were carried out on the ten samples and the results were used to check the
effects used motor oil had on the contaminated samples as compared to the uncontaminated
sample.
xxiv
3.2.1 Mechanical analysis
This test was done on the soil samples to determine quantitative distribution of the different
particle sizes. The samples for the experiment were sun dried and gently disaggregated without
breaking the grains; the weight of the sample was obtained. The sieves to be used were cleaned
and the weight of each was obtained. The BS sieves 4.75mm, 2.36mm, 1.18mm, 0.600mm,
0.425mm, 0.300mm, 0.212mm, 0.150mm and 0.075mm were used for this analysis. The sieves
were arranged to have the largest (sieve 4.75mm) at the top of the stack and the least
sieve(0.150mm) at the bottom. The pan was placed below the sieve 0.150mm and the soil sample
was carefully poured into the top sieve and covered with the cap cover. The sieve stack was
placed in the mechanical shaker and allowed to shake for 15 minutes.
The sieve stack was removed from the shaker and each sieve including the pan was weighed and
recorded with the soil sample retained in it.
Particle size distribution curve was plotted for each of the samples.
This procedure was used to determine the grain size distribution of both the lateritic and the
clayey sand soil materials. The unified soil classification system was used to classify these soil
materials.
xxv
3.2.2 Specific gravity
Test equipment: 50ml density bottle, oven, weighing balance, graduated cylinder.
The specific gravity test was carried out on all the ten samples. The density bottle method was
used to determine the parameter. The density bottle was washed and dried in the oven at the
temperature of 105oC. The weight of the bottle and the stopper is obtained with a weighing
balance. Also, the bottle is filled with clean distilled water and the weight obtained. 5g of ovendried sample was put in the cleaned bottle and the weight obtained. The sample in the bottle is
then filled with clean distilled water and re-weighed. Throughout the care is taken to wipe off the
excess water from the body of the liquid. This same procedure is carried out on all the samples
and the specific gravity is obtained using the expression;
G=
M2 – M1
(M2 – M1) – (M3 – M4)
Where; M1 = mass of empty bottle
M2 = mass of the bottle and dry soil
M3 = mass of bottle, soil and water
M4 = mass of bottle filled with water only.
G = specific gravity
xxvi
3.2.3 Permeability
Test equipment: permeameter mould, dummy plate, compaction rammer, detachable
collar, water supply reservoir, filter paper, stop watch.
The permeability test was carried out using the constant-head permeameter. 2.5kg of thoroughly
mixed wet soil was put in the permeameter mould. The soil was compacted 2.5kg rammer. After
compaction, the collar and the base plate of the mould are removed and weight determined. A
filter paper is placed on the porous discs and the drainage cap is fixed using washers. The water
source is connected and the water is allowed to flow upwards till it has saturated the sample.
After the sample saturation, the water source is disconnected from the outlet at the bottom and
the constant-head reservoir is connected to the drainage cap inlet. The stop watch is started and
the water flowing out of the base into a base measuring flask is collected for a time interval. This
test procedure is carried out on all samples.
3.2.4 Atterberg limits
Test equipment: casagrande’s device, grooving tool, oven, spatula, weighing balance,
ground glass plate, and moisture content can.
The consistency limit or Atterberg limits as mostly referred to is the degree of firmness of a fine
grained soil (Arora, 2010). Also, it could be referred to as the water contents at which the soil
changes from one state to the other.
The consistency limits here was carried out by the casagrande method. The test was carried out
in two stages; the liquid limit determination and the plastic limit determination.
xxvii
Liquid limit: A portion of the soil was taken into the moisture can for moisture content
determination. A portion of the soil is then mixed with some distilled water to a paste of uniform
consistency.
A portion of the paste is placed in the casagrande’s liquid limit device and then leveled up with
the spatula of a smooth straight edge. A groove is made through the center of the paste in the cup
using the grooving tool. The handle of the casagrande apparatus is then carefully rotated and the
cup is lifted and dropped. The rotation is continued until the groove has closed through a
distance of 10mm along the bottom. The number of blows to achieve this is recorded. The test is
repeated until two consecutive runs give the same or nearly the same number of blows in order to
achieve the closure. A portion of the paste is quickly taken for moisture content determination.
The whole procedure is repeated as more water is added to the same sample until, at least, four
different water contents have been obtained at convenient spreads.
Plastic limit: A small portion of the soil is thoroughly mixed with distilled water and then rolled
into a ball. The ball paste is rolled with light pressure between a smooth glass and the palm of the
hand until a thread starts to form. When the thread is about 3mm thick, the thread is inspected for
cracks. It is then kneaded together and rolled out into a thread again. When the soil thread
reveals cracks when it is 3mm thick and a portion of the soil is quickly collected for water
content determination.
This whole procedure of consistency limits determination was carried out on all the ten samples
and the results compared.
xxviii
3.2.5 Compaction test
Test equipment: compaction mould (1000ml), compaction rammer (2.6kg), detachable
base plate, detachable collar, weighing balance, large mixing tray, trowel, straight edge.
20kg of the already prepared soil is put in the mixing tray. Large grains are removed by handpicking. About 4% of water is added to the soil in the mixing tray and the soil is thoroughly
mixed uniformly. The soil is the divided into three equal portions. The mould with the base plate
is weighed after setting it up. The set up is slightly greased.
One portion of the soil is put into the mould and it is compacted by giving 25 blows of the
rammer. The blows should be uniformly distributed over the surface. After the first layer has
been compacted, the second layer is added and also compacted by giving 25 blows of the
rammer. The third portion is also compacted this way. The collar is then detached after
compaction and the soil is leveled, the weight determined. Some sample is removed from the top,
middle and bottom for water content determination.
The soil is removed back into the mixing tray, 6% of water is added and the whole procedure is
repeated again.
3.2.6 Triaxial test
Test equipment: proving ring, dial gauge, weighing balance, stop watch, sampling tube,
split mould, sample extractor, straight edge, and large mould.
The soil sample is prepared at the desired water content in the large mould. The sampling tube is
then pushed into the large mould and then removed with soil filling the tube. The split mould is
then coated with a thin layer of grease. Using the sample extruder, the sample in the tube is
extruded into the split mould and the weight of the mould with the specimen is determined.
xxix
Using a suction pipe, the sample is transferred into a semi-permeable membrane (mostly used is
the condom). The kipp is placed at both sides of the sample and a rubber ring is used to hold it in
place to keep it air tight. The whole set-up is placed in a triaxial machine. The first sample is run
at 10psl and its read-off at the stress dial gauge. The second sample ran at 20psl while the third is
at 40psl.
xxx
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Mechanical Analysis
The results of the mechanical analysis are shown by the plotting below (Figs 5 and 6).
The coefficient of curvature for the lateritic soil is 1.0 while that of the clayey sand material is
1.03. For a well graded soil, the value of the coefficient of curvature lies between 1 and 3 (Arora,
2010). Therefore both soil materials are well graded since there coefficient of curvature fell into
the required range.
4.2 Specific gravity
The value of the specific gravity for both soil materials reduced as the percentage of the
used automotive oil increase. Automotive oil has a lower specific gravity to water. It ranges from
880 – 940 while that of water is 1000. The values of the specific gravity of the contaminated
lateritic material ranging from the 4%, 6%, 8% and 10% were 2.51, 2.35, 2.33, and 2.25
respectively compared to the uncontaminated sample which was 2.66. This can also be observed
on the values of the test for the clayey sand material which had the values of 2.45, 2.41, 2.38,
and 2.35 for the 4%, 6%, 8% and 10% oil contamination respectively as opposed to the control
sample which had the value of 2.70. This implies that oil will always sink in water and this is the
reason why the value of the specific gravity of both soil materials reduces as the percentage of
oil increases.
xxxi
Table 2: Summary of test results
Lateritic soil
Clayey sand soil
Control
4%
6%
8%
10%
Control
4%
6%
8%
10%
sample
Cont.
Cont.
Cont.
Cont.
sample
Cont.
Cont.
Cont.
Cont.
1.0
-
-
-
-
1.03
-
-
-
-
2.66
2.51
2.35
2.33
2.25
2.7
2.45
2.41
2.38
2.35
Permeability 2.75
2.50
2.33
2.05
1.85
1.97
1.86
1.82
1.75
1.70
2.01
1.94
1.91
1.88
1.86
1.92
1.88
1.85
1.81
1.79
39
31
28
24
21
51
59
62
65
68
Mechanical
Analysis
(Cc)
Specific
Gravity
(cm/sec)
Compaction
(MDD)
Triaxial
(Kpa)
xxxii
Percentage finer passing ( %)
120
100
80
60
40
20
0
0.01
0.1
1
10
Grain size (mm)
Fig. 5: Distribution curve for the lateritic material
xxxiii
120
Percentage finer passing (%)
100
80
60
40
20
0
0.01
0.1
1
10
Grain size (mm)
Fig. 6: Distribution curve for the Clayey sand material
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4.3 Permeability
The permeability of both soil materials were clearly affected as compared to the
uncontaminated. The coefficient of permeability for the uncontaminated lateritic material was
2.75cm/sec while the value for the same material contaminated with 4%, 6%, 8% and 10% are
2.50cm/sec, 2.33cm/sec, 2.05cm/sec and 1.85cm/sec respectively. More so, the coefficient of
permeability for the clayey sand material was also affected by the presence of the oil. The
uncontaminated clayey sand material had coefficient of permeability value of 1.97cm/sec while
that of the contaminated samples were 1.86cm/sec, 1.82cm/sec, 1.75cm/sec and 1.70cm/sec for
the 4%, 6%, 8% and 10% oil contamination respectively. The decrease in the permeability of
these contaminated samples is attributed to the clogging of the inter-particle spaces by the engine
oil (Zulfahmi et al, 2010). The presence of engine oil reduced water seepage and the condition
worsens as the percentage of the oil contamination is increased.
4.4 Atterberg limits
The plasticity index (PI) of the oil contaminated samples was reduced as the rate of
contamination increased. The hydrocarbon in the soil samples reduced the water content at the
liquid limit and the plastic limit. The presence of hydrocarbon which is a non-polarized liquid
has caused the reduction of the water film thickness around the clay minerals (Khamechivan et
al, 2007). Water is a binding agent between clay minerals and its orientation which provides the
plasticity characteristics, but this plasticity characteristic cannot be exhibited if the clay minerals
are surrounded by oil films.
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4.5 Compaction Test
The results from the moisture-density relationship show that the presence of the motor oil
has an effect on the compaction characteristics of the soil. The compaction curve graphs of both
soil materials are shown below ( Figs 7 and 8).
The curves derived from the compaction test shows the uncontaminated lateritic soil tends
towards the top right side of the graph having a maximum dry density of 2.01g/cm3 and an
optimum moisture content of 12.2%. The addition of oil brings the curve lower and to the left of
the graph and curves become lower and tends more towards the left of the graph as the
percentage of oil added increases. The MDD values of the 4%, 6%, 8% and 10% contamination
rate is 1.94g/cm3, 1.91g/cm3, 1.88g/cm3 and 1.86g/cm3 with their respective OMC values of
11.4%, 10.1%, 9.8% and 8.6%. The oil present in the soil occupies the soil voids causing
reduction in moisture content thereby reducing the maximum dry density value of the soil. In this
situation, soil becomes difficult to be compacted (Rahman et al, 2010). More so, the
contaminated soil particles slide over their surfaces due to the presence of the oil. This prevents
the repacking of the soil particles as they are being compacted and a poor value of the maximum
dry density.
The MDD for the uncontaminated clayey sand material was 1.92g/cm3 with OMC value
of 11.6%. The soil material followed the same trend as the lateritic material by decreasing in
density as the percentage of oil is increased. At 4% oil content, the MDD for the clayey sand
material was 1.88g/cm3 and at 6% oil the MDD reduced to 1.85g/cm3. The decrease continued
with the 8% and 10% oil contents which were 1.81g/cm3 and 1.79 g/cm3 respectively. These
decreases could be attributed to the presence of the oil causing the reduction in moisture content
and also reducing the binding activities of moisture to clay. The presence of water in clay helps
xxxvi
to bind the clay particles together and make them resistant to pressure to some extent. The
introduction of a contaminant and in this case, used motor oil cause the clay particles to slide
over another making it impossible to bind.
It can be seen in the curves above that there is reduction in maximum dry density with increasing
oil contents. This reflects the effect of lubrication imparted by the soil due to the presence of
engine oil in it, which facilitates compaction due to slippage of soil particles in empty voids and
hence reduce the amount of water needed to reach maximum dry density (A. Pandey and Y.K.
Bind, 2014).
xxxvii
zero-air void
line
2.05
control
2
dry density (g/cm)
1.95
4%
1.9
6%
8%
1.85
10%
1.8
1.75
0
2
4
6
8
10
12
14
16
moisture content (%)
Fig. 7 Compaction curves of the contaminated lateritic soil as compared to the
uncontaminated
xxxviii
1.95
zero-air void line
control
dry density (g/cm)
1.9
4%
6%
1.85
1.8
8%
10%
1.75
1.7
0
2
4
6
8
10
12
14
16
moisture content (%)
Fig. 8: Compaction curves of the contaminated clayey sand material as compared to the
uncontaminated
xxxix
4.6 Triaxial test
The result of the triaxial test for the uncontaminated lateritic material as shown in figure
9 has a cohesion of 39kpa and internal friction angle of 13.060 while that of the clayey sand
material has a cohesion of 51kpa and the internal friction angle of 15.70o (Fig. 10). An obvious
change in the behavior of the materials was noticed when 4% of the used motor oil was added to
each of the soil materials. For the lateritic material, the cohesion dropped to 31kpa while internal
friction angle decreased to 12.05o while that of the clayey sand material increased to 59kpa and
the internal friction angle reduced to 11.560 (Figures 11 and 12). The trend continued at the 6%
and 8% contamination for both soil materials as the lateritic soil has a cohesion of 28kpa and
24kpa with both internal friction angles of 10.900 and 9.160 for the respective percentage
contaminations (Figures 13 and 14) while the clayey sand material has a cohesion of 62kpa and
65kpa with both internal friction angles of 8.560 and 5.720 for the respective percentage
contaminations (Figures 15 and 16). At the last percentage contamination (10%), the drop in
shear strength continued. The cohesion and internal friction angle values for the lateritic material
was seen to be 21KN/m2 and 7.960 respectively (Figure 17) while that of the clayey sand
material was 68KN/m2 for the cohesion and 3.890 for the friction angle (Figure 18).
The presence of the engine oil contaminant obviously reduced the soil strength of the lateritic
material as the percentage of contamination was increased. This fact can be attributed to the
viscous nature of the engine oil. The engine oil being a viscous liquid coats the soil particles with
oil blanket and subsequently increase inter-particle slippage in the soil (Rahman, 2010). But the
internal friction angle of the lateritic material followed a decreasing trend. As the oil content
increased, the internal friction angle of the clayey sand material also decreased. This could be
attributed to the vigorous movement of the soil particles trying to arrange themselves in the
xl
presence of the oil. The oil brings a slippery state within the soil and as such the soil particles are
trying to find a balance thereby decreasing the internal friction angle.
The cohesive strength of the clayey sand material exhibited an increasing trend. The more the
contaminant, the more the increase in cohesive strength. The nature of the clayey sand material is
that of the brittle state. The particles are scattered and hardly form a paste in the presence of
moisture. Motor oil belongs to the category of soil binders because of its viscous nature. When it
comes in contact with the clayey sand material, it binds the particles together thereby increasing
the cohesive strength of the soil material.
xli
Fig. 9: Triaxial test for the uncontaminated lateritic material
Fig. 10: Triaxial test for the uncontaminated clayey sand material
xlii
Fig. 11: Triaxial test for the 4% oil contaminated lateritic material
Fig. 12: Triaxial test for the 4% oil contaminated clayey sand material
xliii
Fig. 13: Triaxial test for the 6% oil contaminated lateritic material
Fig. 14: Triaxial test for the 6% oil contaminated clayey sand material
xliv
Fig. 15: Triaxial test for the 8% oil contaminated lateritic material
Fig. 16: Triaxial test for the 8% oil contaminated clayey sand material
xlv
Fig. 17: Triaxial test for the 10% oil contaminated lateritic material
Fig. 18: Triaxial test for the 10% oil contaminated clayey sand material
xlvi
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS.
5.1 CONCLUSIONS
From the results of this study, the specific gravity of both soil materials was seriously affected.
The lateritic material has its uncontaminated value of 2.66 but kept reducing as the percentage of
contamination increased. Also, the clayey sand material has its uncontaminated value of 2.7 but
was obviously reduced as the oil contamination increased.
The permeability of both soil materials was also affected. It can be noticed that the presence of
the oil contaminant in different degrees reduced the soil permeability.
The compaction and the triaxial tests carried out on the materials identified that the shear
strength of the soil materials were drastically affected as the percentage of the used motor oil
contaminant increased. The author based on the results of this research work concludes that
increased contamination of the soil with used motor oil affects the engineering properties of the
soils negatively by reducing the shear strength of the soil and also reduces the permeability,
specific gravity and maximum dry density of the soil.
xlvii
5.2 RECOMMENDATION
It is recommended that proper engineering soil test should be carried out on a building
site that was previously a mechanic workshop before any structure is erected although the extent
at which the soil is affected depends on the duration of the contamination. Different weather
conditions will also play its role. There should be proper way of disposing used motor oil in
Nigeria, and a monitoring agency can be setup to ensure that all mechanic workshops adhere to
proper disposal of used motor oil in our dear country Nigeria.
xlviii
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