Determination of swelling and collapse characteristics of unsaturated soils involve the study of the stress volume change behaviour with the variation of moisture content. The best known and most popular procedure utilized for this is the oedometer test. It has been reported that values of swelling pressure and collapse potential were found to vary dramatically. This could be attributed to various factors such as boundary and placement conditions, preparation of sample as well as experimental difficulties that arise when testing unsaturated soils. The present paper is a part of a comprehensive and broad research work for studying some of the problems that pertain directly to laboratory testing of unsaturated soils. It is based on standard techniqueswith the intelligent utilization of the one dimensional oedometer apparatus. This part of the research work presents results obtained from studying the effect of some of the factors on the value of swelling pressure such as method used, side friction between sample and ring in the oedometer and deformability of the apparatus. Also techniques to reduce or minimize their effect for better and accurate measurements of swelling pressure are introduced and discussed.
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