Mechanism Of Vacuum Preloading And Numerical Analysis Considering Inconstant Well Resistance

With the rapid development of coastal cities in recent years,reclamation engineering and other urban construction engineering is becoming more and more,however,these districts have poor geology and massive soft clay which means that it needs a foundation reinforcement before construction.As one of methods of foundation reinforcement,vacuum preloading has a widely application because of its powerful advantages.However,the mechanism of vacuum preloading is disputed.the conventional numerical analysis don't have comprehensive consideration.the deficiency of traditional construction technology is increasingly outstanding.These problems have limited the theoretical development and the practical application of vacuum preloading.This paper which begins with the mechanism of vacuum preloading and covers the analysis of inconstant well resistance in practical engineering,achieves 3D finite element analysis of vacuum preloading considering inconstant well resistance through introducing the inconstant well resistance mathematical model into 3D finite element analysis and simplifying 3D finite element model.Otherwise,the new construction technology and improved technology of vacuum preloading in recent years are introduced in this paper.Main content of each chapters is as follows:?1?Through summing up massive scholars' researches and analysis about reinforcement mechanism of vacuum preloading method,this paper argues that the underground water level will have a fall in the process of vacuum preloading and the effect depth of vacuum preloading is greater than the limit of vacuum preloading water depth of 10.3 m.Then,the microscopic mechanism of vacuum preloading method is explained from the mechanism of vacuum transmission,the mechanism of drainage consolidation and the strength mechanism three Angles,which is easier to understand.?2?According to field observation and laboratory test,it is found that the inconstant well resistance effect is widespread in vacuum preloading.The main factors affecting variable well resistance includes: lateral pressure,deformation of PVD,deposit and jam,quality of PVD and construction factors,and the inconstant well resistance mathematical model is also given according to these influencing factors.?3?Facing the problems of great difficulty of 3D modeling and failing to consider inconstant well resistance effect in element analysis,a new finite element unit,which can vastly reduce the difficulty of 3D modeling and can introduce the inconstant well resistance mathematical model by basing on the secondary development of ABAQUS platform,is proposed in this paper which means that the way of 3D finite element analysis of vacuum preloading considering inconstant well resistance effect is reached.Taking a reclamation project in Tianjin Port as an example,the 3D finite element model is set up to compare the calculated data with the measured data,and then a sensitivity analysis on the inconstant well resistance parameters is also analyzed.The results enunciate that the calculation result considering inconstant well resistance effect is mostly closer with the measured data.The parameter of a₂ has a greater influence on consolidation compare to the parameter of1 A.?4?On the basis of introduction of traditional construction technology of vacuum preloading,the improvement plan to traditional vacuum preloading method is proposed from three approaches which are the plate core and the filter of PVD,quantities of sand cushion and pressing system of vacuum preloading,which has great reference value for practical application.