Degradation Study Of The Soft Clay Foundation Of Yangtze Estuary Waterway

In early Dec, 2002, attacked by a cold wave, most of caissons, whichhad been mounted on the rock foundation in middle north bank sector ofYangtze Estuary waterway, founded failure appearance sinking and slippageat different degree. For the sake of the sedimentated foundation, triaxial testswere implied to compare intensity before and after oscillation of soft clay byunconsolidated-undrained(UU) tests. The reasons that soft clay of YangtzeEstuary waterway was degraded under the wave cyclic loading weretestified.The outcomes of compared static/dynamic triaxial tests indicate theaverage intensity of soft clay is 14.7kPa in static unconsolidated-undrained(UU) triaxial tests and the average intensity is 5.32kPa after oscillation ofsoft clay in dynamic triaxial tests. The ratio of intensity is 0.36 .Theoutcomes testify the intensity of soft clay will occur to be strongly degraded(softening) phenomena.The outcomes of compared dynamic/ static triaxial tests indicate theratio of average intensity of the consolidated-undrained (CU) soft clay underthe consolidation load is 0.83 after and before oscillation. The soil is notdestroyed because the strain is less than 4.5% when the cyclic load isrepeated for 1000~3000 times. It indicates the capability of resistingdegradation should be greatly enhanced when the consolidation degreereaches 85% under the consolidation load.In this paper, PLAXIS program is carried out to study and comparedegradation of the saturated soft clay before and after consolidation underthe wave cyclic loading and outcomes of dynamic triaxial tests are testified.It provides scientific evidences for the degradation of soft clay under thewave cyclic loading.