Compression Index versus Natural Water Content Relationshipsfor China's Coastal Soft Clays

A large number of C-c - w(n) (C-c is the compression index and w(n) is the natural water content) correlations have been proposed by researchers for different soft clays around the world, but comparisons of these correlations and reasons for differences between them are rarely reported. In this paper the C-c - w(n) relationships of marine soft clays from eight China's coastal cities are presented. It is found that the north coast clays have larger slope of the C-c - w(n) relationships (about 0.02) than the south coast clays (about 0.008). Comparisons with C-c - w(n) relationships for remoulded clays and structured natural clays reported by other researchers show the importance of accounting for soil structure, and the higher compressibility and higher apparent preconsolidation stresses of the north coast clays, in comparison to the south coast clays, are believed to be associated with chemical bonding and other post-depositional changes. Most of the reported C-c - w(n) correlations for natural soft clays from around the world have slopes of about 0.011, which are applicable to weakly structured clays. To develop a more widely applicable C-c - w(n) correlation, the effects of soil structure need to be incorporated.