Abstract:

A series of laboratory tests were conducted of intacted samples of the 2nd to 6 th Shanghai clays to investigate fundamental physical properties of successive upper clay layers in Shanghai, and overconsolidation behaviors were studied through a series of standard oedometer tests and triaxial consolidated drained compression tests. Natural water content, initial void ratio, liquid/plastic limit and liquid/plastic index were found to have similar trends of variations with depth change. Due to gentle curvature of the compression curve over the preconsolidation pressure range, the work method proposed by Becker was cited to obtain the yield pressure in oedometer test, which showed that the overconsolidated ratio (OCR) of the 2nd and 6th layers were larger than 2, while those of the 3rd and 4th were about 1.15, and that of the 5th were closed to 1.40. Different characteristics of stress-strain curves in drained triaxial tests of the 2nd to 6th Shanghai clays reflect the distribution of OCR obtained in the oedometer test. The unite study method composed by oedometer and triaxial tests will contribute to further understanding of the overconsolidated behaviour of soft clays with weak structure.

Key words: Shanghai clays, overconsoli dated ratio (OCR), work method, weak structure, labortary test