Geotechnical Properties of Clayed Soils in Mixed Marine and Terrestrial Deposit

Abstract

Cohesive soils of the mixed marine and terrestrial sediment are deposited along the north side of the Yangtze River estuary of China. The natural deposit has poor physical properties, with natural water content close to or greater than the liquid limit and the void ratio close to or greater than one. These properties are similar to those of natural soft marine clays, while the former has much higher in-situ shear strength and sensitivity. To investigate the reason for the abnormal combination between the poor physical properties and the relatively good mechanical characteristics, a series of field and laboratory tests were performed on the natural mixed deposit. The results of oedometer tests and corresponding micro-structural tests under different consolidation stresses indicate that the natural mixed deposit is normally consolidated and are structured. There is a good uniformity between micro-structural change and macro-mechanical properties. It is found that the existence of structure is an essential factor, which causes the good mechanical behavior of the natural mixed deposit. The unique sedimentary environment and depositional texture of the natural cohesive soils are the direct reason that has resulted in the abnormal combination between the bad physical indexes and good mechanical characteristics.