Nonlinear Finite Element Analysis Of Deformation And Stability On High Subgrade Using Nonlinear-elastic Model

The deformation and stability of soils are still the two basic questions that the high fill subgrade confronts with. Engineering practice shows that it is a close relationship between them, and before the failure of a slope there is always a big vertical settlement and lateral deformation. For the sake of highway's line-type, especially, as the height of subgrade increases, it has been gradually becoming a key concern in the building of high-class highway in mountain areas. How to improve and perfect the measure, and ensure the stability of the high shape, is still under studying in our country. Then the study of constitutive law has changed a situation. That is, for a long time, the deformation analysis uses the linear-elastic model and stability analysis uses the rigid-plastic model. But from the strength of stress-strain to the development of stability, it is a continual process.Because of above reasons and for further research on the varying criterion of deformation and stability on high fill embankment. In the dissertation, the author adopts the nonlinear-elastic model — Duncan-Chang model, and based on the theories of the nonlinear finite element. Some corresponding nonlinear finite element program in FORTRAN is presented. Through the task Yong-Zhang high fill subgrade, Fujian, China. Then according to the production of airport engineering, highway engineering, and dam engineering, the theory analysis is done.1. Numerical simulation analyses of the high fill subgrade, are carried out with nonlinear FEM Total Stress Method. The characteristic of stress field, displacement field and stress level are gotten. Furthermore, considering the load of highway structure and vehicle load, and through converting them to equivalent nodal load, the increased displacements are also obtained.2. After considering the fill material as saterated soils, then adopting Biot consolidation theory of saturated soils, the developments of self-compression with time, pore-water pressure with time are given. For the fill engineering the most danger time is the completed time, as the time goes by, the filling gets safety. 3. Through using the slope stability analysis by strength reduction FEM on the high subgrade, the safety factor and the surface of sliding are calculated. The results are found to be in good agreement with those by using the Bishop method. Besides, the incremental displacements at failure are obtained.Study shows that the nonlinear FEM analytical results agree with other's researches and the field investigations.