| The post-construction settlement of soft soil foundation is one of the indexes which measure the effect of soft soil treatment. Excessive post-construction settlement affects driving performance and quality of roads seriously. There are a variety of soft soil treatment methods and the applicabilitis and effects vary a lot. Now, the treatment method selection still relies on the experiences, which results in the occurrence of excessive post-construction settlement. In order to control the post-construction settlement effectively, the research on post-construction settlement and treatment method selection should be conducted. Soft soil spreads widely over Lianyungang and the treatment quantity is huge. In this thesis, the basic characteristics of the soft soil and the main treatment methods in Lianyungang are analysed. The prediction and analysis of post-construction settlement based on observational data of Lian-yan Freeway are conducted. The influence factors of post-construction settlement are analysed by using Plaxis (a finite element software). The treatment method selection program based on post-construction settlement is given at last.Firstly, the basic characteristics of the soft soil and the main treatment methods in Lianyungang are analysed. The basic characteristics of soft soil are summarized, including the formation and distribution, basic physical and mechanical properties, shear strength, consolidation deformation and creep. The main treatment methods used in Lianyungang conclude proloading, cement mixing pile and rigid pile. The using proportion, characteristics, applicabilities, treatment effectiveness and economy comparison of these methods are also analysed.Secondly, the prediction and analysis of post-construction settlement based on observational data of Lian-yan Freeway is conducted. The accuracy and applicability of sevral curve models used to predict the post-construction settlement are compared. Hyperbolic model and sectionalized hyperbolic model are proved to be reasonable. The characteristics of post-construction settlement are got by analyzing the stettlements of the sections along the freeway.Thirdly, the influence factors of post-construction settlement are analysed by using Plaxis. The finite element model of deep treatment sections is built and the influences of pile length, pile spacing and pile modulus are analysed. Also, the model of shallow treatment is built and the influcences of soft soil thickness, embankment height, crust lying thickness, preloading height and preloading time are analysed. The sensitivity analysis of influence factors using orthogonal test and calculation equation of post-construction settlement of shallow treatment sections are also conducted.Finally, treatment method selection program based on post-construction settlement is given. Post-construction settlement is choosen as one of the main influence factors of treatment method selection. The level, the weight and the evaluation methodlolgy of influence factors are anlaysed. Treatment method selections of two typical sections are given to prove the applicability of the selection program. |
