JWSS - Journal of Water and Soil Science

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Expansive soils swell and shrink periodically when subjected to seasonal water content changes. As a result, they are a constant source of problem in the design and construction of foundations. In this study, the behaviour of an expansive soil was studied through a number of experiments involving cycles of wetting and drying using three different water qualities. Laboratory tests were performed on statically-compacted samples of an expansive soil in a modified Oedometer under constant surcharge pressure of 10 kPa. Vertical deformation of the soil sample was recorded continuously, and during the test, void ratio and water content of the sample were determined at different stages. The results indicated that the equilibrium condition was reached after about six wetting-drying cycles. It is shown that the swelling potential changes with changes in water quality the saline water reduced the swelling potential of the soil compared to the distilled water during wetting and drying cycles. Furthermore, the results showed that the variations of water content-void ratio paths during wetting-drying were the same (no hysteresis) when the equilibrium condition was achieved

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Some recent research has indicated that certain alkaline contaminations may adversely affect mechanical properties of clayey soils. To examine the potential impact of alkaline divalent barium on the swelling characteristics of KAHRIZAK clay, the major solid-waste landfill at south of Tehran, a systematic set of experiments was conducted. Observations indicated that the swelling in the studied soil that belonged to the CH-MH group with a PI of 28.44, was reduced by about 17, 37, 48 and 54 percent, and swelling pressure by about 41, 55, 65 and 67 percent, respectively, after addition of barium chloride solutions to concentrations of 0.25, 0.5, 0.75 and 1.25 molal. It was also found that addition of barium chloride solutions to concentrations of higher than 1 molal had a little effect on reduction of swelling and swelling pressure.

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To deal with the destructive effects of swelling soils, different methods have been proposed by researchers. Chemical stabilization of expansive soils is one of the effective methods that are low-cost and efficient economically and technically. Recently, with the improvements of nano science in nanomaterials production and application, using this type of materials has been considered in different sciences especially geotechnical engineering. In this research, the effect of adding different amounts of nanoclay on swelling behavior modification of two types of clayey soils with low plasticity and high plasticity has been studied. For this purpose, first, identification tests were implemented on two types of clayey soils and nanoclay. Then, swelling potential tests were conducted on samples of soils with different amounts of nanoclay including (0, 0.25, 0.5, 1 and 2 weight percent) considering curing ages of 3 and 10 days. The results showed that the effect of adding nanoclay to the high plastic soils swelling potential is more than adding it to that of low plastic soils. So, adding 0.25 to 0.5 weight percent of nanoclay reduces the swelling potential of high plastic soils about 67 percent, and that of low plastic solis about 3 percent. Furtheremore, the maximum reduction in swelling potential increases by adding up to 0.5 percent nanoclay; and decreases for adding amounts more than 0.5 percent.