Study On The Mechanism And Settlement Computation Method Of Prefabricated Drain Preloading

Among soft-base improvement methods, prefabricated drain preloading is one of the most popular vertical drain methods. It is developed from sand drain preloading method. With the development of country economy, the method was used widely in soft ground reinforcement of several lands of civil engineering projects, such as road, port, airdrome, and so on. And favorable effect is obtained. However, there are some flaws and dispute about improvement principle and design theory.Based on the former research, several works in this paper is listed as follow, which is studied by experiment research, theoretical analysis and numerical calculate:Firstly, based on local observation and laboratory experiment result, consolidation mechanism of vacuum-surcharge preloading is analyzed form typical mechanics and microstructure seepage factor. A great deal of observed dada is employed to analyze the deformation characteristics of soil after being treated and variation law of pore water pressure.Secondly, the shape of reinforcement area which have a great influence upon the effect is discussed here, effective embedding depth of plastic drain board and the applying conditions for prefabricated drain preloading method are researched. Combined with practice project, a new unloading criterion is proposed.Thirdly, a calculation formula of distortion settlement is established by considering soil structure damage and plastic drain board restraining displacement of soft foundation. Starting with discussing the main factors affecting settlement of consolidated foundation, a reasonable method to modify the calculated settlement of soft foundation by layer-wise summation method is presented here. With calculable coefficients of volume deformation, lateral displacement and structure damage to modify the settlement will be closed to measurer settlement. Based on studying main factors affecting secondary settlement, a method to estimate the post-construction settlement after removal of surcharge is proposed.Fourthly, compared with calculate results for typical section of a culvert soft-base reinforcement project in the water way to sea of Huaihe river engineering by the plane strain FEM based on Biot consolidation theory, measured data and simple calculation result, the simple calculation method proposed in this paper is proved to be reasonable and verified, and is more referenced by congener project.