边桩对PBA法黄土车站地表变形的影响分析

研究目的:边桩作为PBA法施工中主要的承重构件之一,其参数对控制车站变形具有重要意义。因此,本文以西安黄土地区某PBA法施工的地铁车站为背景,分别研究不同入土深度和直径对地表和边桩变形的影响规律,从而为黄土地区PBA法施工边桩参数选取提供参考。研究结论:(1)地表沉降曲线沿车站中线轴对称分布,中间沉降量最大,向两边减小;边桩水平位移曲线呈现"鼓肚"形式;(2)地表的沉降量及边桩的侧向位移随入土深度的增加而减小;随着直径的增加,地表下沉和边桩的侧向位移逐渐减小,减小速率随着相关参数的增加而减小;(3)从变化幅度来讲,入土深度达到承载力和稳定性要求后,增加入土深度对改善边桩位移影响较小;适当增加边桩桩径,可以有效改善边桩的水平位移;(4)入土深度对塑性区的分布范围具有重要意义,入土深度过小会产生较大的塑性区,影响结构的整体稳定性;(5)本研究成果可为日后黄土地区PBA法施工边桩参数选取提供一定的参考依据。

Analysis of the Influence of Side-pile on the Surface Deformation of Loess Station by PBA Method

Research purposes:Side pile is one of the main load-bearing members in PBA construction,and the parameters of side pile are of great significance to control the deformation of station.Therefore,based on a metro station constructed by PBA method in Xi’an loess area,this paper studies the influence of different depth and diameter of soil entry on the deformation of surface and side pile,which provides a reference for the selection of side pile parameters of PBA method in loess area in the future.Research conclusions:(1)The surface settlement curve distributes symmetrically along the middle line of the station,and increases gradually from both sides to the middle.The horizontal displacement curve of side pile shows the form of"bulging belly".(2)With the increase of the depth of soil entry,the settlement of the surface and the lateral displacement of the side pile decrease.With the increase of the diameter,the surface subsidence and the lateral displacement of the side pile decrease gradually.The reduction rate decreases with the increase of related parameters.(3)From the point of view of variation amplitude,when the depth of soil entry meets the requirements of bearing capacity and stability,increasing the depth of soil entry has little effect on improving the displacement of side pile.The horizontal displacement of side pile can be effectively improved by properly increasing the diameter of side pile.(4)The depth of soil entry is of great significance to the distribution range of plastic zone.If the depth of soil entry is too small,a large plastic zone will be produced,which will affect the overall stability of the structure.(5)The research results can provide some reference for the selection of side pile parameters of the PBA method in the loess area in the future.