The Research Of Tensioned Membrane Effect In The Pile-supported Embankment

Pile-supported reinforced embankment is a new type of foundation treatment methods, through arranged geosynthetics at the top of the pile, to increase the level of resistance system and pile spacing significantly and reduce the engineering cost. Practice shows that, adopting pile-supported reinforced embankment structure has characteristics such as short construction time limit for a project, depth of processing, construction quality easy to control, small impact on adjacent buildings, reinforcement effect is well and so on, it has broad engineering application prospects in highway widening and the weak subgrade treatment of new highways and high-speed railways. However, there is a large difference of the load transfer mechanism from conventional piled embankments and flexible piles with composite foundation, has not yet formed perfect analysis method and design theory currently. In this thesis, combined with the National Natural Science Foundation (No.50908198) and the Graduate School of the Jiangsu Province Innovation Fund (CXLX11-1010), carry on an investigation into pile-supported reinforced embankment tensioned membrane effect through theoretical analysis, model test and numerical analysis. The main achievement and conclusions are summarized as follows:(1) Collected previous research data of pile-supported reinforced embankment, analyzed the applicable conditions and lack of calculation method of the geotextile by various scholars currently, made clear the direction of the research should focus on.(2) Has carried on the research of model test of pile-supported reinforced embankment, analyzed the pile soil stress ratio, the stress reduction ratio,vertical stress distribution in embankment and the variation law of geotextile vertical displacement.Compared the difference between reinforced and unreinforced, one layer and two layers of geosynthetics and compared the tendency of the tension and displacement.(3) Analyzed single-layer geotextile for two-dimensional and three-dimensional numerical analysis, compared the displacement deformation and tension of geotextile between the different working conditions, at the same time, compared the common theoretical calculation methods with two-dimensional and three-dimensional numerical results, pointed out that the scope of application and improvements of the theoretical calculation formula.(4) Multi-layer reinforcement method for the three-dimensional numerical calculation, analyzed the variation of displacement and tension in multi-layer reinforced, and compared the calculated results with the results of numerical calculation in single-layer reinforced, points out the difference that the two types of reinforcement in reinforcement mechanism.