| It is well known that the rheological property is one of the important engineering characters of the soft soil. Numbers of engineering experiences and researching results have showed that the distortion of soft clay does not generate instantly, but increases slowly in a long term. The rheological property of the stress and strain developing with the time of the soft soil becomes a focal issue in engineering practices, because it has important relation with stability and long-life performance of structures. With the rapid development of littoral economy, many capital constructions have been built on the marine soft clay with obvious rheological property in the littoral, consequently, the study of the rheological property of the marine soft clay must be enhanced for avoiding the constructions and foundations instability to issue in heavy loss. In this paper, an important problem about the rheological property of the marine soft clay has been studied, and the major contents and conclusions of this study are as follows:1. By using the improved triaxial rheological test apparatus an indoor creep test with the marine soft clay in Tianjin Port Aera has been finished, creep-time curves with different stress levels have been obtained, and the creep behavior of the littoral soft clay has been studied.2. Based on the indoor creep test, experience formulas and model theory, the non-linear creep constitutive model of the littoral soft clay is established. For expressly and logically describing the littoral soft clay's non-linear rheologic characteristics, the creep constitutive model has the main part making of the rheological unit model, and the other part which is the experience formulas adding the phase of accelerating creep into this creep model. Because of be worked out through deeply analyzing of the creep test curves, the model is simple and intuitive, and has a definite physical purport. According to the creep test data, eleven parameters of the creep model are determined by the numerical approximation. Moreover, numerical results agree well with those of the test data, which provides convincing evidences for the model's excellent solution quality and fidelity.3. By combining the creep constitutive model with one-dimensional Terzaghi consolidation theory, the non-linear creep consolidation sedimentation model of the littoral soft clay has been developed, and proved its rationality by some engineering project. Furthermore, a pre-estimation on long-term creep settlement of the soft clay in Tianjin Binhai New Aera is presented by using the sedimentation model. At the same time, the one-dimensional large-strain and non-linear creep consolidation sedimentation model which be adapted to the saturated soft clay has been deduced from the large-strain consolidation theory and the non-linear creep model. It has been shown that the discrepancy of the creep settlement between large-strain consolidation theory and small-strain one is more evidently with the increase of time.4. The finite elements analysis system of the non-linear creep constitutive model of the littoral soft clay has been founded through inputting the UMAT subroutine which is developed from the creep model into the finite elements soflware ABAQUS. The indoor triaxial creep test is simulated in this finite elements analysis system, and simulant results agree well with those of the indoor test, which well verifying the high reliability and computational capability of the finite elements analysis system. It is feasible that a series of problem of consolidation settlements and stability of the diversified structures in the littoral area can be settled by using the finite elements analysis system.5. Finally, a three-dimension finite elements model of the wharf structure with box-type suction foundation by applying the finite elements analysis system of the non-linear creep constitutive model of the littoral soft clay has been established for the analysis of the horizontal carrying capacity and the long-term stability of the wharf structure.
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