Settlement Analysis Of Plate-layered Soil Systems Under Long-term Repeated Loading

For about half a century, the improvement of foundation design method and soil remedical measures is always a focus problem in the geotechnical engineering field. The settlement is one of the key issues in practice. As a result of comprehensive investigations, it is proved that the settlement arise mainly from the action of long-term repeated loading. It affects directly the using function and service life of structures. In recent years, how to predict the long-term settlement is one of the most difficult problems in the urban transportation construction. The development in theory drops behind practices evidently, and the perfect design theory and the reliability design approach have no been come into being. Therefore it is necessary to conduct a comprehensive research on the behavior of plate-layered soil systems under long-term repeated loading. In this paper, a relatively complete analysis method based on the a modified layered foundation model is put forward for plate-layered soil systems, and then a system research on the deformation characteristics of plate-layered soil systems under long-term repeated loading is made with finite element method, which is based on analytic method, finite element method and experimental study etc. The results are useful in practical engineering and can be references for designers. The studies of this paper consist of the following parts.1. For all kinds of soil, the one-dimension loading laboratory test is repeatly made. The results show that the constrained modulus and the one-dimension resilient modulus are close related with the number of loading and unloading. The constrained modulus and the one-dimension resilient modulus can be obtained from the results of finite numbers of laboratory tests by means of curve fit, and then the soil property parameters used for computing the settlement of plate-layered soil systems can be obtained.2. A modified layered foundation model is proposed in this paper. In traditional layered foundation model, the layer-wise summation method is adopted. But due to its own deficiency, it fails to fully reflect the practical case. To provide more efficient and practical solutions, a more elabora soil model is propsed in this paper.According to the modified model, the Burmister stress solution of multilayered elastic materials is applied to calculate the additional stress in foundation, and the layer-wise summation method is used to calculate the settlement of ground. Compared with the traditional model, the modified one is closer to the reality, and the applicability is wider.3. Based on modified layered foundation model, a FEM method of plate-layered soil systems under loading is put forwarded. Comparisons with present literatures verified the reliability of the present method and program. Furthermore, a FEM method of plate-layered soil systems under long-term repeated loading is presented, which is based on the above FEM, the simulated formula of the compression modulus and one-dimension resilient modulus, and the assumption of elastic computation. At last, it is demonstrated that good effect can be obtained with this method in the actual engineering application.4 An approximate settlement prediction method of plate-layered soil systems under long-term repeated loading is proposed, which is based on the simulated formula of the compression modulus and one-dimension resilient modulus for all kinds of soil, the assumption of elastic computation, and the FEM calculation results under first loading and unloading.