عنوان مقاله [English]
Soil is generally subjected to different contaminants that are being used and excreted into the environment. Leakage of these materials can influence its physical and mechanical characteristics. A review of technical literature in this field shows some contradictions between the results of different research, which reveals the impact of soil and contaminant type on the behavior of contaminated clayey soil. In order to investigate the effects of organic contamination on the physical and mechanical characteristics of clayey soil, in the present study, a series of index tests, besides one-dimensional consolidation (Oedometer tests), has been performed. Two types of clay, Kaolinite and Bentonite, with low and high plastic indexes are used as the base soils. Also kerosene and gasoil are applied as the organic contaminant in four different percentages of 0, 3, 6 and 9 to the base soil. All samples were kept for seven days in polyethylene bags to perform all chemical reactions before
the tests. After that, water is used to saturate all samples normally within 48 hours. Results of physical tests reveal that Atterberg limits increase, by an increase in degree of contamination, for both considered soils. Also, maximum dry density increases with enhancement of the degree of contamination.
However, according to the Proctor compaction tests, the optimum moisture content reduces with degree of contamination. This is illustrated due to the lubrication of grains during contamination with organic material. Consolidation tests are conducted on samples in two distinct relative compactions of 50% and 70%, and the results are investigated in e-Log (p) coordinates. Based on the results of one dimensional consolidation tests, compressibility coefficient increases, with an increase in contaminant percentage for both soils. Also, the
effects of contamination on the consolidation behavior of clay increase with an enhancement in relative compaction. As a result, it is negligible in soil with low relative compaction. Using the results of tests, an empirical relation is suggested between the compressibility coefficient of contaminated soil and its relative compaction and liquid limit. Comparison of the suggested equation with ordinary relations in soil mechanics texts shows a great difference, which proves the necessity for new suggested forms in contaminated soil. Finally, it was concluded that chemical and organic contaminants, like kerosene and gas oil, which are not soluble in water, are more effective in changing the physical characteristics of soil, like Atterberg limits and relative compaction. However, compared to the first category, soluble organic contaminants are more effective on the mechanical and consolidation characteristics of clayey soil.