SWELLING AND COMPRESSIBILITY CHARACTERISTICS OF COMPACTED SAND-BENTONITE MIXTURES

Compacted bentonite-sand soils are commonly used as lining, filling, and capping materials. Swell, compactability, and compressibility characteristics of two groups of compacted bentonite-sand mixtures are investigated. High and low quality bentonites are mixed with pure white silica sand. The percentages of the bentonites in the mixtures are: 10%, 15%, 20%, 25% and 30%. Consistency limits of the mixtures increase linearly as the quanity of the bentonite increases; whereas, maximum dry density reaches an optimal value of 2 Mg/M3 at 20% bentonite for the two groups. Maximum dry density decreases and optimal water content increases with further increase in bentonite percentage. Double oedometer swell tests are performed at 95% maximum dry density and at water content 3% less than the optimum water content. Results indicated that swell potential increases with bentonite percentage and decreases with valence of the interlayer cations. The study emphasises the important role of clay type and percentage, and soil fabric, on the swelling behavior of compacted bentonite-sand mixtures. (A)