| The largest scale Land reclamation is now under way in Chinese Tianjin Binhai New Area, as well as in the world. Its main ingredients is fine grain, in which the proportion of clay mineral are up to 50, among them illite and illite mixed with montmorillonite layer is the most, which are the special source for the hydraulic fill project in the eastern coastal areas of china. Up to now vacuum preloading is the most commonly used method for soft dredger fill, this found treatment can form structural strength in the soil shortly, but its Engineering Property is poor and rheological deformation can not be ignore. As result, it is very complex and difficult to estimate and control the post-construction settlement. At present, all kinds of constitutive model are developing from saturated disturbance soil and sand, little considering the influences of soil structure, so that the calculated value different from the practical situation. Therefore, How to proclaim this inherent law is the complex key issue which cannot avoid in Soil Mechanics now and a long time in the future. Although we have accumulated much experience of foundation treatment for hydraulic fill, the research about engineering properties especially about soil structure, rheology and its model and also its mechanism is obviously behind the engineering practice.In view of the above questions, centering on characteristics of structural , experimental study and theoretical analysis on the formation mechanism of structure, time-dependence of deformation and the relationship between them are implemented based on the previous research in the paper, rheological constitutive model of soft dredger fill considering the structure is proposed. In order to make a progress in the theory of calculation and control of settlement, rheology mechanism is discussed through microstructure. The main work are as follows:1,Through systematically studied the basic characteristics of soft dredger fill of typical treated foundation by vaccum preload, It showed that the main ingredients of it is fine grain which has high clay content, obvious structure formed after vaccum preloading. Only have a full realization of the effect of soil structure on compressibility, strength, relationship of stress and strain and yield stress can we make rational use of the soil structure.2,Based on the designed testing tank to simulate the deposition process of dredger fill in Tianjin Binhai New area, the theory of structural yield stress formation on soft dredger fill in Ko consolidation and isotropic consolidation and creep test after Ko consolidation was proposed through comprehensive investigation.3,Through triaxial rheological test, rheological behaviors of two typical state of soft dredger fill(undisturbed and remold)are compared, the results indicated that the rheological behaviors is distinctly different between them due to the soil structure.4,Two type of rheologcal model considering the soil structure are proposed, which are semi empirical and empirical constitutive model.5,Based on the model established in the paper, the widely used soft Abaqus analysis program is adopted to study engineering project on the hydraulic fill site in Lin-gang Industrial zone. The results proved that considering the influence of structure is the most reasonable constitutive model. So forecasting the rheological behavior and deformation development through this constitutive model maybe the best way.6,The variation of microstructure was proclaimed through analysing the microstructure and the structural strength in the procession of the rheology, this lay the foundation for building the essential characteristics of rheology.
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