洞桩法施工引起土体变形的规律研究

Study of Soil Deformation Caused by Construction with PBA Method

研究目的:洞桩法作为一种修建地下车站的新兴工法,发展迅速,但其已有的研究成果主要集中在地表沉降及管线变形上,忽视了地下结构与土体的相互作用,尤其缺乏对于四洞三跨结构洞桩施工引起土体变形研究。本文以北京地铁16号线苏州街站工程为背景,基于实测数据对导洞开挖阶段地表沉降的发展及分布规律进行分析,并结合有限元方法动态模拟地铁车站洞桩法施工过程,研究四洞三跨结构洞桩法各施工阶段引起的土体变形规律。研究结论:(1)多个相邻导洞同时开挖会引起"群洞效应";(2)对地表沉降影响最大的主要是导洞开挖、初衬施工及二衬施工这三个阶段,占总沉降量的比值分别为32%、55%和7%;(3)二衬施工完后,支护体系初步形成,除开挖面底部土体因卸荷产生竖向隆起外,其他土体主要以水平变形为主:拱顶上部土体向车站中心发生一定水平位移,同时拱顶两侧土体受支护结构伸张变形的影响,向车站外侧发生明显水平位移;(4)本研究结论可为洞桩法的推广与应用提供理论依据,并可为类似工程的施工与设计提供参考。

Research purposes： As a new method of metro station construction, the pile -beam -arch（PBA） tunneling method is developing rapidly. Neglecting the interaction between underground structure and soil, existing research results mainly focus on surface settlement and pipeline deformation. In particular, there is a lack of research on soil deformation caused by the construction of holes and piles in the four - hole and three - span structure. Based on the Suzhou Street Station of Beijing Metro line 16, the law of surface subsidence in the phase of pilot tunnel excavation was studied through the date of field monitoring. Metro station construction was dynamically simulated with FEM to study soil deformation during the construction in the four- hole and three -span structure. Research conclusions： （ 1 ） ＂ Effect of group cavities＂ will appear when a plurality of adjacent pilot tunnels are excavated together. （2） Pilot tunnel excavation, construction of first and second lining have the greatest impact on surface subsidence. The proportions of settlement are 32%, 55% and 7%. （ 3 ） Supporting system formed after finishing secondary lining construction. In addition to the bottom soil that has vertical upheaval due to unloading after excavation, the other soil mainly was mainly horizontal deformation. After station construction, certain horizontal displacement that moves to the center of station raised in the soil over the vault. Horizontal displacement, caused by stretching deformation of the supporting structure, toward the outside station obvious took place in the soil on both sides of the vault and the soil around the pile end moved to metro station. （4） The conclusion can provide a theoretical basis for the popularization and application of the pile - beam - arch （PBA） tunneling method and provide a reference for similar projects in the construction and design.