Numerical and Analytical Evaluation of Crude Oil Contamination Effect on Strip Foundation's Bearing Capacity

In the worldwide some soils are contaminated to crude oil. For example due to seepage from oil transport pipes, soil of refineries were polluted. Because of sensivity of structures in refineries, bearing capacity changes have significant importance. In this study by using 3 types soil's shear strength parameters which made by other researchers by the means of experiment, effect of pollution amount on strip foundations bearing capacity were investigated by numerical and analyti- cal pieces software. Eventually based on ordinary least square method (OLS) empirical equations prepared to calculate reduction in bearing capacity. There is a large volume of published studies describing this fact that is shear strength parameters of soils were changed by hy- drocarbon pollution (e.g. Khamehchian and et.al 2007, Ashraf K. Nazir 2012, Rajaei and et.al 2012 and etc.). In this paper by measured parameters by Khamehchian and his collogues, bear- ing capacity of strip foundation were determined and effects of contamination content and embedment depth were studied. Material Properties and Methodology In this research by measured parameters by Khamehchian and his coworkers bearing capacity of strip foundation by 2 meter width placed on low activity clay (CL), poorly graded sand (SP) and silty sand (SM) with different embedment depth calculate by using 3 methods and effect of contamination content and embedment depth were studied. In Khamehchian research, soils by 0,4,8,12 and 16 percent of dry weight are contaminated with crude oil. Embedment depth over base width ratio which consider in this paper are equal to 0, 0.25, 0.5 and 1. Method which used to determine bearing capacity are Hansen classic method, FIDES software which work based on DIN standard and finite element software PLAXIS. Thank to insignificant dif- ference among results, to study effect of contamination, average of 3 methods results was used. In Plaxis software, Mohr-Columb Elastic-plastic model was used. Specific weight, internal friction angle and cohesion with different contamination percentage are prepared in tables 1 to 3. Table 4 shows geometric parameters of foundation. TABLE - 1 CL Soil properties