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.

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 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). 

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 watercontent and Atterberg limits properties with increases in oil contents.

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 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.