Abstract: One-dimensional and isotropic consolidation tests were carried out on clay of varied depth in Shanghai to acquire the compression index C_c and the rebound index C_s and their relations with parameters parameters λ and κ in the modified Cambridge model. However, laboratory tests are time-consuming and expensive. Empirical relations need to be developed to predict compression index using physical indices (especially natural water content w_n, initial void ratio e₀, liquid limit w_L and plastic index I_p) of soil which are relatively easier to obtain. Highly linear relations between C_c/n₀ and C_c as well as C′_s/n₀ and C′_s were found, and corresponding relational expressions were established. Hence, the deformation index of soft soil in Shanghai can be estimated by void ratio. In addition, according to test data of soft soil in coastal areas in China, including Guangzhou, Tianjin, Shenzhen, Wenzhou, and Fuzhou, an empirical function between C_c/n₀ and C_c was constructed to predict compression index of soft soil in some coastal areas in China (Guangzhou, Tianjin, Shenzhen, Wenzhou, and Fuzhou) for preliminary engineering design.

Key words: soft clay, one-dimensional consolidation, isotropic consolidation, compression index, swelling index, empirical correlations, coastal areas