Abstract: Compression index obtained from the oedometer test is required for calculation of ground settlements. However, oedometer test is very time consuming and expensive, and requires a lot of experience for obtaining undisturbed soil samples from the field. Equation needs to be developed in order to predict compression index using index properties of soil which are relatively easier to obtain. Intact samples are taken in Shanghai area using thin-wall samplers, and are conducted by oedometer tests. The data used for the study consist of current and existing laboratory results from several geotechnical investigation reports. Natural water content has good linear correlation with initial void ratio, but not obvious with liquid limit. Since water content is more easier to obtain than initial void ratio, it is used to predict compression index. Commonly used linear equation is not suitable for Shanghai clay, especially when water content is higher than 45%. Finally, an exponential function involving the water content is recommended to predict compression index of upper Shanghai clay for preliminary engineering design. The function is also verified by compression index of clays at other places in coastal area of eastern China.

Key words: Shanghai clay, compression index, consolidation test, natural water content, exponential function