For the stability problem of surcharge loading on soft foundation for the causeway construction in the Yangtze River Estuary,we carry out a series of stress path tests under different loading patterns,and analyze the stress-strain relationship,structural damage characteristics,strength and strain rate development for the soft clay in the Yangtze River Estuary to provide technical references in the construction rate selecting and the stability control in the construction for this project.The results show that the undrained shear strength of the soil,without concerning the influence of consolidation,is almost independent on the loading pattern.The ultimate strength is independent of the strain at failure,and it shows strongly interacted with the loading time and the standing time.In addition,the strain rate at instability of soil is related to the loading rate and the standing time,and the loading rate is more predominant.The soil sample is nearly failure when the maximum stage-strain rate gradually deviates from the linear tendency or the surcharge loading reaches over 80% of the undrained shear strength.