Vacuum Combined Loading To Preload Test And Simulation Analysis

The high-speed development time of passenger railway construction in our country is coming. The most pivotal technical problem of building high-speed railway on soft soil is strictly controlling post-construction settlement of subgrade. Comparing with the traditional methods, The combined method of vacuum-surcharge preloading is feasible and widely used in treating soft ground with several advantages such as saving money, shortening time and so on. However, there are some flaws and disputes about reinforce mechanism and numerical analysis about this method.Based on the former researchers′work, several aspects of the matter 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) Firstly, the development and current research of vacuum preloading were introduced. The consolidation mechanism and consolidation characteristics were researched, and the Numerical calculation method of consolidation was given out.(2) Based on the site, the law of consolidation settlement was summarized, which is useful to guide the engineering practice. The analytic parameters of the soft embankment were obtained by the methods on site survey and indoor experiments.(3) A numerical simulation model, through Lagrangian difference method, was founded, in which the mutual coupling relations of the water and soil in the process of consolidation were fully considered. Based on the Mohr-Coulomb model and the considering of gradual increase load and negative pore-water pressure boundary condition, consolidation settlement process of the soft ground was calculated and analyzed. By comparing the finite difference computation to the situ experimentation, we found it is feasible to actualize the numerical simulation of vacuum-surcharge preloading soft ground through Lagrangian difference method. (4)The issue about numerical simulation of the vacuum was discussed. and more, a contrastive analysis, to simulate the vacuum independently through negative pore-water pressure boundary and equivalent load, was carried out. The results indicated there were few differences in the final settlement of the soft ground through the two methods, however, the time-settlement curve during vacuum preloading period, simulated by negative pore-water pressure boundary, was more similar to the actual condition.