Abstract
Problem statement: Oil contamination due to accidental spillage or le akage brings hefty damage to the environments. It percolates steadily into subsurface environments and contaminates the soil and water system. Hydrocarbon contamination has not just affected the quality of the soil but wil l also alter the physical properties of oil-contamina ted soil. Approach: This study presented the geotechnical properties of oil-contaminated soils a s well as uncontaminated soils for comparison. Testing programs performed on the studied soils inc luded basic properties, Atterberg limit, compaction, permeability and unconsolidated undrained triaxial tests. The base soils used were originated from weathered basaltic rock of grades V and VI. Soil samples were artificially contaminated with 4, 8, 12 and 16% oil of the dry w eight of based soils. Results: The results showed that the oil contamination decreased the liquid lim it and plastic limit values for both grades of weathered soils. For soil grade V, the decrease in plastic limit and liquid limit were represented by 21 and 39%, respectively. Meanwhile, for soil grade VI , the drop was significantly high for liquid limit (39%) and lower for plastic limit (19%) if compared to soil grade V. The oil-contaminated soils also indicated a lower Maximum Dry Density (MDD) and optimum water content if compared with uncontaminated soils. The MDD for soil grade V and VI decreased from 1.67-1.50 and 1.60-1.55 g cm -3 , respectively. The OMD values dropped from 23.5-17.5% for soil grade V and 23.0-16.5% for soil grade VI when oil contents were increased. A reduct ion in permeability was observed as a result of the oil contamination. The permeability of soil g rade V and VI decreased from 3.74-0.22 and 2.65-0.22 cm sec -1 , respectively. In terms of undrained shear strengt h, Cu was clearly affected by the increase in oil content in contaminated soils. Both soil grades showed stress dependant behavior with a brittle mode of failure. The C u values for uncontaminated soils of both grades wer e 126 and 106 kPa and then dropped to very close values of 35 and 32 kPa at oil content of 16%. Conclusion: The results showed that the addition of oil has adverse effects to the geotechnical properties of the studied resi dual soil. Contaminated residual soils might be used for geotechnical purposes and these results will benef it to engineers or decision makers in recycling or re- using of contaminated soils.
Highlights
Accidental oil spillage or leaking has caused severe damage to the environment
Hydrocarbon contains undissolved components of Dense Non-Aqueous Phase Liquid (DNAPL) and Light Non-Aqueous Phase Liquid (LNAPL) which can travel vertically or horizontally in long distances under gravitational influence which require different treatment depending on the nature and extent of contamination (Zogala et al, 2009)
The purpose of this study is to present some of studied geotechnical properties of oilcontaminated soil originated from weathered basaltic rock of grade V and VI, in terms of consistency limits, compaction effort, permeability tests and soil shear strength
Summary
Accidental oil spillage or leaking has caused severe damage to the environment. Oil contamination can adversely affect the soil microbes and plant as well as contaminate groundwater resources for drinking or agriculture (Hong et al, 2005). The purpose of this study is to present some of studied geotechnical properties of oilcontaminated soil originated from weathered basaltic rock of grade V and VI, in terms of consistency limits, compaction effort, permeability tests and soil shear strength. It is vital to understand the behavior of oil-contaminated soil since many of this weathered earth material is widely being used in many geotechnical works e.g., landfill liner, embankment, base material and backfill. Sample preparation and experimental program: Base soil for preparing contaminated samples was collected from two profiles to represent the weathered basaltic soil of grade V and VI. These disturbed samples were collected using auger at 30 cm below the ground surface. Seven uncontaminated soils were initially analyzed for index properties and classified as per unified soil classification scheme
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