Abstract: A sort of silty clay which has both high hydrophilic clay mineral contents and high liquid and plastic limits exists in the swampy and lacustrine plain in Yangcheng Lake area of Suzhou..Although it has certain swelling and shrinkage properties in the natural state,it doesnt belong to classical expansive soils.But while this soil is disturbed and compacted,with the dry density increasing and water content decreasing,its swelling and shringkage properties become very apparent.Hence the remolded clay can be called man-made expansive soil.Through analyzing the outcome of the experiments on the soil samples taken from the three earth-fetching areas on the northeast of Yangcheng Lake,from which the earth for the road base is collected,this paper discusses the special properties of the silty clay in this area and provides the scientific guidance for the future construction.