Analytical And Field Evaluation Of Deep Basements And Their Corresponding Heights In High-Rise Buildings For Top-Down Construction Method

The development of our modern society,particularly in big cities,makes the construction of basements of a great necessity.A basement serves as a space for car parking and housing utilities of various kinds.Due to the demand for construction and underground space in urban areas,onefloor basements have become unable to meet the increasing demand of people.This study chooses Nanjing Jinmao Plaza II,in Nanjing-China,as a case study using a top-down construction method.This method was selected in this project due to the complex construction environment of the city,and the strict requirements of the deformation,which made the traditional excavation engineering methods more challenging.The top-down construction method has been used widely in urban areas,particularly in high-rise buildings with basements,so that the sub-structure and super-structure works can be carried out simultaneously to save time and improve safety.The purpose is to provide perfect design ideas and analysis methods in the development of deep foundation excavation supporting systems.The main content of this study are as follows:1.A short overview of top-down method showing background and significance of this technique,different applications in the world,the basic principles of classification and characteristics of this method,current construction design of the Top-down method,field investigations for technical tests and their in-situ applications,test results for a case study.2.Study of finite element theory by top-down method.Including the finite element basic principles of different analysis phases,the soil constitutive model,and the excavation process’ s top-down method for the finite element mesh simulation.3.According to the numerical finite element simulation in PLAXIS 3D;analysis with the construction of soil excavation and basement structure and their corresponding heights in high-rise buildings for top-down construction method,the effect of adding additional floors to the superstructure during the excavation work for the foundations causes settlement for the supporting diaphragm wall.Likewise,the condition of the column piles experiences the same effect according to the different construction stages.Therefore,this work analyzes and summarizes the construction guidelines for the top-down construction method in order to ensure the safety,optimize design,and apply previous recommendations of this construction technology to provide a reference for this promising technique.