Deep Excavation Pile Anchor Bracing Optimization Research And Numerical Simulation

With the quickening pace of urbanization, urban land becomes less and less lack.All kinds of high-rise buildings and underground project constructions are underconstruction, which increase the number of foundation pit excavation. It is bound tohave influence on the surrounding of the building (structure), underground pipeline andmunicipal facilities. In order to reduce the influence of excavation on the surroundingenvironment, the foundation pit supporting must be carried out. If the demand of thesurrounding construction is high, and the geologic site condition is complex, the controldeformation and stability of foundation pit are particularly important.Taking Ji’nan Bin’he Business Center as the engineering background of deepfoundation pit project, according to the foundation pit supporting structure securitylevels as a benchmark to the deformation and stability of foundation pit and requirement,combing with foundation pit surrounding environment and the geological andhydrological conditions, this thesis selects pile anchor bracing as foundation pitsupporting type. Based on the geological condition, hydrologic co ndition, surroundingenvironment and construction condition, this thesis selects expanding head of anchorcable as prestressed anchor cable. Through the design documents, theoretical analysisand numerical simulation in three working conditions to design the foundation pitsupporting, this thesis analyzes the influence of the three conditions on soildisplacement and bending moment of pile, and anchor cable internal force, to determinethe optimization model of the pile anchor supporting, in other word namely pile andexpansion anchor combined support (sac expansion anchor head). The main researchcontent is as follows:1、On the basic theory, the pile anchor supporting system composition, workingprinciple, calculation methods and deformation characteristics, and especially analysesthe basic composition, working principle, calculation method and applicable conditionsof the expanding body of anchor cable (sac expansion anchor head).2、Based on Ji’nan Bin’he Business Center deep foundation pit engineering, usingFLAC3D finite difference software, this thesis establishes a three dimensional numerical model for foundation pit, simulating the whole process of foundation pit excavation.3、Using FLAC3D to simulate three conditions including pile, pile and anchor ropecombined support the expansion body, and pile and expansion anchor rope combinedsupport respectively, this thesis analysis deeply the working condition of the soildisplacement, bending moment of pile, and the bearing capacity of anchor cable.Finally, based on synthesize of the comprehensive of foundation pit deformation andstability of each working condition requirements, this thesis determines the optimalsupporting type, namely the anchor pile and the expansion body (sac type expansionanchor) support.