Numerical Simulation Analysis Of Construction Deformation Of The Whole Top-down Method Process

Inverse construction method is a new type of foundation pit supporting technology,which is related to the development of city construction into the sky and underground,traffic facilities to the multi-level three-dimensional development.Comparing to the normal foundation supporting pit technology,the inverse construction method takes the apparent advantages in environmental protection,energy saving,underground space utilization efficiency.It overcomes the disadvantages of traditional engineering technology and sustainable,not only in efficiency of the construction of the underground space in high-rise building,and also conforms to the general direction of constructing economical society.However,due to inverse construction method is a preliminary application in excavation engineering in foundation pit supporting system.In the design theory and construction technology,it is still needed to research in the deep areas.The purpose is going to provide perfect design ideas and analysis method in the development of deep foundation pit supporting inverse construction method.This paper includes the following aspects:(1)Based on the foundation project for XuRi high-rise apartment building in Rongcheng.theoretical derivation,the code formula and the method of the elastic support model are adapted to study the influence of vertical bearing capacity of structures of top-down method.The upper structure's internal force variation and the changes of maximum subsidence point position for vertical pile's uneven settlement and maximum moment and shear on the beam are also explored.(2)It simulated all the stages in inverse construction according to data of PLAXIS 3D.Through each construction process under the model unit of displacement and internal force of change,analyzed the deformation,pillar and support vertical displacement and internal force of pile the post,it concluded the deformation trend of the foundation pit after construction,and the axial force of angle,side and center column inside in the foundation pit under different construc-tion phase as well as the column changing with depth curve and the bending moment distribution curve.Furthermore,According to the step by step curve in angle,side column and center of the column,the paper contrasted analysis of their variation patterns are summed up.Then,it concluded their transformation rule.(3)According to the PLAXIS 3D finite element numerical simulation,in order to research the influence of construction deformation of the top-down method,it simulated the negative influence of the top-down method during construction period due to improper construction caused by the tilt of the column,pile subsidence of the adverse situation.And then,analysis the construction after the completion of the tilted columns and column pile sinking of pillar pile internal force and the influence of the beam internal force and deformation.Finally,normal construction under internal forces and inclined,pile sinking internal forces are compared in angle and the middle column under the condition of internal forces separately.That provides the basis for the next step of construction safety.