| Large-diameter cylinder, a kind of new structures, is well attended all over the world. The reason for this is that it has a lot of advantages, such as adapting to soft silty groundwork, low cost, quick construction, and good durability. As a matter of the complexity from itself as well as inner and outer soil's affection, the existing simplified and numerical methods, all have obviously different results. Undoubtly, the method of its stability has become the key problem for its application.This paper has combined simplified and numerical methods'characteristics to research. With calculation and analysis, two methodological results get preferably inosculation. This has inaugurated a new direction for the combination of simplified method and 3D numerical method in the future.In the aspect of simplified model, at present, most methods are under the hypothesis that cylinder turns around a point of its axes. In this paper, there are two probable displacement models presented on the assumption that a cylinder may turn around a point either in the axe or in the generatrix. Moreover, this paper has improved the design method of cylinder stability based on anchorless sheet pile. Aimed at different loading states, it presents four calculation models. Accounting to the structure's response to load, the model which based on cylinder turns around a certain point in the generatrix is more suitable to the facts. Thus it recommends using this model as the reference calculation method for the embedded depth of a large-diameter cylinder.For the 3D numerical analysis, nonlinear finite element analysis software ABAQUS has been applied, which has used the depth which is resulted from the model presented. Amendatory Drucker-Prager model helps to proceed the analysis of 3D elastic and elastic-plastic finite elements. With the increment of exterior load, the largest displacement of silty surface and the obliquity of cylinder both increase in the two models, and the elastic-plastic model makes those aggrandize more quickly. In the same depth and lower load condition, the datas of two models are nearly the same. Comparing two elastic-plastic finite element models under two different depths, it's proved that the embedded depth has great effect on the stability index, such as the largest displacement of silty surface and the obliquity of cylinder. So the calculation of large-diameter cylinder's embedded depth is a key problem in the stability design. It is suggested using the models based on cylinder turns around a certain point in the generatrix to calculate the embedded depth; then estimating cylinder stability with the results from 3D elastic-plastic finite element analysis of the largest displacement of silty surface. |
