The Research On The Creep Of The Soft Clay And Its Application In The Pile Foundation Engineering Of The Abutment

The stress and strain developing with the time, which is called rheology, is the especial engineering characteristics of the soft clay. The rheological trait of the soft clay includes creep, stress relaxation, elastic aftereffect and long-term strength. Creep is one of the hottest issues in engineering practice. Because of the creep trait, many bridges those built in weak subgrade have encountered a lot of problems, such as the subsidence of the floor behind the abutment, the cambering of the floor before the abutment and the forward movement of the abutment itself, which have done great harm to the transportation and the security of the bridge.Firstly, through deeply study of the rheological theory and the typical rheological curve of the soft clay, an improved nonlinear elastic-viscous elastic-viscous plastic model is presented and the corresponding constitutional equation has been worked out too. Secondly, based on the principle of the indoor creep direct shear test, the direct shear apparatus is designed and fabricated. Thirdly, by using above apparatus an indoor direct shear test with the parent soil in Jiangmen City, Guangdong Province, has been finished and a great deal of experimental data are obtained. Then, according to the experimental data, the Genetic Algorithms method with the virtues of intelligence and parallelism is used to back analyze the parameters in the constitutional equation and the theoretic curves fit the actual ones very well. Moreover, on the "time step-viscous initial strain" theory, a FEM procedure, which can analyze the reological problems of the whole system of pile-abutment-ground has been worked out on the floor of Visual Fortran 6.5. This procedure can also be used for forecasting the qualities such as displacement or stress of the pile or the soil in different periods, which will give some qualitative reference to the engineering design. Finally, all above results are used in the supportive engineering practice, and the displacement vector diagrams, the stress and strain contour diagrams are obtained. At the same time, the contrastive analysis of the displacement of the piles and the soil pressure has been done as to whether consider the creep effect or not. The last results indicate that the curve considering the creep effect matching the actual curve much better.