Land, air and water are being contaminated for short-term benefitsby industrial, petrochemical, construction, and sanitary activities.
Considering land contaminations, environmentalists are concerned aboutsubsurface water aquifer contaminations, plant growth in contaminated soil, andenvironmental and health hazards. On the other hand, geotechnical expertsshould consider the effects of soil contamination on the geotechnicalproperties of the soil. The soil-bearing capacity, foundation settlement, shearresistance, compressibility, and plasticity are the factors that must be takeninto consideration. Crude oil is one of the mostcommon soil contaminants. Over two million tons of oil are produced all overthe world every day, and about 10 percent is entering the environment due topipeline breaks, leakage from reservoir tanks, tanker accidents, discharge fromcoastal facilities, and offshore petroleum productions. For instance, the destruction of Kuwait’s oil production facilitiesat 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 Iranencounters oil pollution due to historical oil exploitation and related tankernavigations, accidents, and petrochemical sewage (Kermani and Ebadi, 2012).
Oil contamination can adversely affect thesoil microbes and plant as well as contaminate groundwater resources fordrinking or agriculture (Hong et al., 2005). Hydrocarbon itself can separateinto solid, liquid and gaseous phases which either remain closely to theleaking places or migrate within the groundwater system or absorbed on grainsas an immobile residual fluids. The properties of soils and migrationsubstances control the rate of migration, changes of composition and propertiesof migration substance. Al-Sanad et al (1995) studied thecompaction, CBR and permeability characteristics of oil contaminated sand. Fourdifferent 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 studyrevealed that the compaction characteristics and CBR values improved up to 4 %oil by weight in sand. They further reported that the permeability valuedecreased with the increase in content of oil in sand but the changes were notsignificant.
A laboratory testingprogram was performed to determine the effects of crude oil contamination onsome of the geotechnical properties of clayey and sandy soils from the coastalsoils from Persian Gulf beaches by Khamehchiyan et al. (2007). Their testingprogram examined basic properties, Atterberg limits, compaction, direct shear,uniaxial compression, and permeability on clean and contaminated soil samplesthat had the same density.
Their study reveals that theoptimum water content, maximum dry density and permeability decreases with theincrease in crude oil content in sand.Cleaning of oil-contaminated soilcommonly depends on excavating the material followed by subsequent treatment,incinerator or disposal in landfill. This usually involves a complicated taskespecially located under storage facilities by virtue of high cost and limiteddisposal facilities of excavated soil (Shah et al., 2003). The hydrocarboncontamination will not just affect the quality of the soil but will also alterthe physical properties of oil-contaminated soil.
This will lead togeotechnical problems related to construction or foundation structure on thisoil-contaminated site. Most associated impacts of oil contaminant are excessivesettlement of tanks and breakage of pipeline (Mackenzie, 1970). The utilizationof highly weathered soil for road base led to causes of damage from rainwatererosion and traffic (Millogo et al., 2008). Attempt has been made to useoil-contaminated sand in asphalt concrete for secondary road material(Al-Mutairi and Eid, 1997). Jamrah et al.
(2007) investigated the geotechnicalproperties of untreated contaminated soils of Oman and comparison had been madewith the treated soils. A microscopic study on oil-contaminated clay was alsopresented by Habib-ur-Rahman et al. (2007) in order to understand the fabricand interaction between oil and clay mineral under Scanning Electron Microscope(SEM).
Meegoda and Ratnaweera (1994) studied the compressibility behavior ofcontaminated fine-grained soils of low plasticity and high plasticity clays (CLand CH). The results showed that compressibility is controlled by themechanical and physicochemical factors, they proposed correction factors toaccount for the change in the compression index caused by the viscosity of porefluid. Professionalengineers and scientists have suggested several remedial methods foroil-contaminated lands.
These included the conversion of oily soil to road basematerial or topping layers for car parks and roads after mixing with aggregateor consolidation agents. Other methods include containment in large burialsites, incineration, biological methods, absorption methods, soil washingmethods, 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, andcompressibility of oil-contaminated sand obtained from eastern Saudi Arabia. Hefound that the compressibility and permanent deformation of theoil-contaminated sand increased as the temperature increased above roomtemperature and that the shear strength parameters were not sensitive to thetesting temperature.Puri (2000) evaluated the geotechnical aspects of oil contaminatedsoils through laboratory testing on sand samples. The test results indicatedthat the compaction characteristics are influenced by oil contamination.
Theangle of internal friction of the sand based on the total stress condition wasfound to decrease with the presence of oil in the pores. One-dimensionalcompression characteristics of sand are significantly influenced by oilcontamination, which results in a decrease in the value of the constrainedmodulus as the degree of oil saturation increases. Hydraulic conductivity wasobserved to be a function of the initial viscosity and the degree of oilsaturation.Shin and Das (2001) studied the bearing capacity of unsaturatedoil-contaminated sand.
Based on their test results, oil contaminationdrastically reduced the bearing capacity of sand. This paper presents the results of a comprehensive laboratorytesting program that was designed to determine the effects of crude oilcontamination on sandy soils in the Lajan site. The tested properties includeshear strength parameters and compaction characteristics.