Explicit Dynamic Nonlinear Finite Element Numerical Simulation Of Improving Fly Ash Embankment By Dynamic Compaction

With the development of the national economy, the emission and accumulation offly ash are increasing year by year. As urbanization and industrialization continue toincrease, China’s land resources increasingly tense, a lot of projects have to been builtin the fly ash accumulation area. The fly ash foundation belongs to the soft soilfoundation, and its bearing capacity is too low to satisfy the needs of engineering. So,we must carry on the processing to meet the bearing capacity, stability and antideformation capacity requirements. With its simple construction process, goodeconomy, great reinforcement effect, dynamic compaction has been widely applied inthe field of fly ash foundation treatment.However, compared with the wide applications in actual projects, the theoryresearch of dynamic compaction is laggard. The complexities of dynamic compactionprocess determine that the analytic solution is too difficult to calculate accurately. Thereinforcement mechanism and design theory are still not mature, and site constructionmainly relies on the experience formula and field test, this greatly limits thedevelopment and application of dynamic compaction method. The traditionalnumerical methods are based on the assumption of small deformation, while in actualprojects compaction zone will have a large deformation, the results are often not justas one wishes. With the development of numerical calculation methods, explicitdynamic nonlinear finite element theory becomes more mature and provides a newchoice for nonlinear large deformation problems like dynamic compaction. Inresearch of dynamic compaction of common soil types such as collapsible loess,gravel soil and aeolian sand, explicit dynamic nonlinear numerical method hasoccupied a space for one person and achieved certain results. However, its applicationin fly ash foundation is still blank.In view of this, firstly, this article introduces explicit dynamic nonlinear finiteelement theory, and compares it with implicit theory to find the differences betweenthem. Then, based on explicit dynamic nonlinear finite element analysis method,dynamic compaction is analyzed by using ANSYS/LS-DYNA software, the generalsteps of explicit dynamic nonlinear numerical simulation method are concluded.Combined with the example of an embankment compaction of a highway, athree-dimensional model of the compaction process is simulated to get reinforcement range and fields of stress and displacement. By comparing with the field data, thisnumerical simulation method is proved to be applicable. On this basis, the dynamiccompaction treatment of fly ash embankment in Yueyang is researched. By modelingthe two construction plans, the problem of rammer selection is studied. The analysisof the results of numerical simulation and comparison of the soil settlements afterdynamic consolidation show that choosing a heavier hammer under the same energylevel will have a better reinforcement effect.