Abstract
Naturally deposited marine clays are usually in overconsolidated state notwithstanding they have not been subjected to release of the overburden because of the additional strength developed by aging effect, such as by secondary compression and chemical bonding. These effects on undrained strength characteristics, such as 1) stress-strain characteristics, 2) overconsolidation ratio, 3) K0 value and 4) anisotropy in undrained strength are discussed for alluvial marine clays found in the Arabian Gulf and in the Tokyo Bay.It is first shown that clay shows more brittle behaviour as the strength developed by secondary compression and chemical bonding becomes greater. It was found from the study that overconsolidation ratio of the clays investigated can be obtained from the strength ratio between in the field and in normaly consolidated state and that strain value at failure in strength tests shows almost a constant value independing on overconsolidation ratio. In addition, it was strongly suggested that K0 value and anisotropy in undrained strength (which is a stress induced anisotropy that results from rotation of principal stress during shear) of the clays are independent on overconsolidation ratio and almost the same as the values in normally consolidated state.
