Land, soil microbes and plant as well as

Land, air and water are being contaminated for short-term benefits
by industrial, petrochemical, construction, and sanitary activities.
Considering land contaminations, environmentalists are concerned about
subsurface water aquifer contaminations, plant growth in contaminated soil, and
environmental and health hazards. On the other hand, geotechnical experts
should consider the effects of soil contamination on the geotechnical
properties of the soil. The soil-bearing capacity, foundation settlement, shear
resistance, compressibility, and plasticity are the factors that must be taken
into consideration.

 Crude oil is one of the most
common soil contaminants. Over two million tons of oil are produced all over
the world every day, and about 10 percent is entering the environment due to
pipeline breaks, leakage from reservoir tanks, tanker accidents, discharge from
coastal facilities, and offshore petroleum productions. For instance, the destruction of Kuwait’s oil production facilities
at the end of the Gulf War resulted in the massive pollution of the ground
(Al-Sanad et al., 1995). As another example, the southern coastal plain of Iran
encounters oil pollution due to historical oil exploitation and related tanker
navigations, accidents, and petrochemical sewage (Kermani and Ebadi, 2012).

 Oil contamination can adversely affect the
soil microbes and plant as well as contaminate groundwater resources for
drinking or agriculture (Hong et al., 2005). Hydrocarbon itself can separate
into solid, liquid and gaseous phases which either remain closely to the
leaking places or migrate within the groundwater system or absorbed on grains
as an immobile residual fluids. The properties of soils and migration
substances control the rate of migration, changes of composition and properties
of migration substance.

Al-Sanad et al (1995) studied the
compaction, CBR and permeability characteristics of oil contaminated sand. Four
different types of petroleum products such as benzene, Al-Ritga heavy crude,
Rawdatain light crude, and Al-Zoor gas oil were used in this study. Their study
revealed that the compaction characteristics and CBR values improved up to 4 %
oil by weight in sand. They further reported that the permeability value
decreased with the increase in content of oil in sand but the changes were not
significant. A laboratory testing
program was performed to determine the effects of crude oil contamination on
some of the geotechnical properties of clayey and sandy soils from the coastal
soils from Persian Gulf beaches by Khamehchiyan et al. (2007). Their testing
program examined basic properties, Atterberg limits, compaction, direct shear,
uniaxial compression, and permeability on clean and contaminated soil samples
that had the same density. Their study reveals that the
optimum water content, maximum dry density and permeability decreases with the
increase in crude oil content in sand.

Cleaning of oil-contaminated soil
commonly depends on excavating the material followed by subsequent treatment,
incinerator or disposal in landfill. This usually involves a complicated task
especially located under storage facilities by virtue of high cost and limited
disposal facilities of excavated soil (Shah et al., 2003). The 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 site. Most associated impacts of oil contaminant are excessive
settlement of tanks and breakage of pipeline (Mackenzie, 1970). The utilization
of highly weathered soil for road base led to causes of damage from rainwater
erosion and traffic (Millogo et al., 2008). Attempt has been made to use
oil-contaminated sand in asphalt concrete for secondary road material
(Al-Mutairi and Eid, 1997). Jamrah et al. (2007) investigated the geotechnical
properties of untreated contaminated soils of Oman and comparison had been made
with the treated soils. A microscopic study on oil-contaminated clay was also
presented by Habib-ur-Rahman et al. (2007) in order to understand the fabric
and interaction between oil and clay mineral under Scanning Electron Microscope
(SEM).Meegoda and Ratnaweera (1994) studied the compressibility behavior of
contaminated fine-grained soils of low plasticity and high plasticity clays (CL
and CH). The results showed that compressibility is controlled by the
mechanical and physicochemical factors, they proposed correction factors to
account for the change in the compression index caused by the viscosity of pore
fluid.  

Professional
engineers and scientists have suggested several remedial methods for
oil-contaminated lands. These included the conversion of oily soil to road base
material or topping layers for car parks and roads after mixing with aggregate
or consolidation agents. Other methods include containment in large burial
sites, incineration, biological methods, absorption methods, soil washing
methods, and vacuum extraction and separation by centrifuge and screen systems
(Al-Sanad et al., 1995).

Aiban
(1998) studied the effect of temperature on the strength, permeability, and
compressibility of oil-contaminated sand obtained from eastern Saudi Arabia. He
found that the compressibility and permanent deformation of the
oil-contaminated sand increased as the temperature increased above room
temperature and that the shear strength parameters were not sensitive to the
testing temperature.

Puri (2000) evaluated the geotechnical aspects of oil contaminated
soils through laboratory testing on sand samples. The test results indicated
that the compaction characteristics are influenced by oil contamination. The
angle of internal friction of the sand based on the total stress condition was
found to decrease with the presence of oil in the pores. One-dimensional
compression characteristics of sand are significantly influenced by oil
contamination, which results in a decrease in the value of the constrained
modulus as the degree of oil saturation increases. Hydraulic conductivity was
observed to be a function of the initial viscosity and the degree of oil
saturation.

Shin and Das (2001) studied the bearing capacity of unsaturated
oil-contaminated sand. Based on their test results, oil contamination
drastically reduced the bearing capacity of sand.

 

This paper presents the results of a comprehensive laboratory
testing program that was designed to determine the effects of crude oil
contamination on sandy soils in the Lajan site. The tested properties include
shear strength parameters and compaction characteristics.

 

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