Soft Subgrade Drainage Consolidation And Finite Element Analysis

Among soft-base improvement methods, prefabricated drain preloading method is one of the most popular vertical drain methods. It is developed from sand drain preloading method. With the economic development of nation, the method was widely used in soft ground reinforcement of many civil engineering projects, such as road, port, airdrome, etc, and expecting results are achieved. However, there are some flaws and disputes about improvement principle and design theory.Based on the former research, much work has been done in this paper, which is studied by the methods of on-site experiment, theoretical analysis and numerical calculation. It is listed as follows:(1) The analytic parameters of the soft embankment are obtained by the methods on site survey and indoor experiments;(2) Through the in-site observation data, it could come to the following conclusion: during the precompression period, the settlement of the soft embankment shows a good hyperbolic relation with time. So the hyperbolic curve method can be used to predict the total settlement and the residual settlement at any moment of the soft embankment.(3) The two kinds of elastoplastic model (Mohr-Coulomb model and Cambridge model) are discussed in the paper. A concrete project example was analyzed with the large-scale finite element software—ADINA. The two kind of computed results were compared with the on-site results. And some advantageous results to next project application were obtained.(4) Established a finite element analysis model of the soft embankment, in which the mutual coupling relations of the water and soil in the process of consolidation is fully considered. The plane finite element analysis of the soil body has been carried out by using effective stress principal, in which the soil characteristics of non-linearity, large strain are considered.(5) The instantaneous settlement is analyzed in the paper, and the proportion of the instantaneous settlement in the total settlement is also obtained. By the comparison the results of the finite element computation to the theoretical analysis computation we found that the proportion of instantaneous settlement in the finite element computation is very large, and it almost comes to 30～50%.