双线盾构扩建地铁车站的插管冻结法及施工力学特性研究

Insert-Tube Freezing Method for Expanding Construction of Metro Station Based on Double-Line Shield Tunnel and Its Mechanical Characteristics

盾构施工是地铁区间隧道的首选施工方法,但盾构区间与车站在施工速度和组织上的矛盾,会导致盾构长距离掘进的优势无法充分发挥。本文在总结以往国内外“先盾后站”技术的基础上,提出基于洞内插管冻结的双线盾构区间隧道扩建地铁车站的施工方法。首先,对该技术的施工流程、关键技术、适用条件、技术优势与缺陷等进行详细论述;然后,基于有限元模型,采用以壳单元模拟冻结管、以加固圈模拟冻结土体、以刚度折减法模拟管片接缝的方式,对双线盾构插管冻结扩建地铁车站施工过程中的结构变形、受力及地表沉降特性等进行分析。最后,得到如下结果:1)得出了扩建施工所引起的地表变形规律及最大沉降值;2)明确了既有盾构结构随施工过程的变形阶段;3)确定了扩建施工过程中既有盾构及托梁、立柱的受力敏感区域;4)有针对性地提出了既有盾构管片的加固方案和防水措施。本文研究的目的在于阐明双线盾构区间隧道扩建地铁车站的插管冻结法及其施工力学特性,为盾构区间与车站施工矛盾、无拆迁条件必须“甩站”通过等工程问题提供一种有效的解决途径。

Shield is the preferred method for tunnel construction in metro sections.However,due to the contradictions of construction speed and organization between shield sections and metro stations,the advantage of the shield method in long-distance tunneling could not be fully used.Based on summarizing the technology of"shield first and then station"in China and abroad,an expanding construction method for metro stations based on double-line shield tunnel using insert-tube freezing method is proposed.First,the construction process,key techniques,applicable conditions,technical advantages,and defects of the construction techniques are discussed in detail.Second,based on a finite element model,the frozen pipes are simulated using shell elements,frozen soil is simulated using reinforcement circles,and the segment joint mode is simulated using the stiffness reduction method;and the characteristics,such as the structural deformation,load-carrying capability,and surface settlements during the expanding construction of a double-line shield tunnel are analyzed.The results are obtained as follows.(1)The law and maximum value of surface settlement caused by the expanding construction are obtained.(2)The deformation stage of the existing shield structure with the construction process is clarified.(3)The force-sensitive areas of the existing shield,supporting beams,and columns during the expanding construction are determined.(4)The reinforcement scheme and waterproofing measures of the existing shield tunnel segments are proposed.This study aims to clarify the insert-tube freezing method for expanding the construction of metro station based on double-line shield tunnel and its mechanical characteristics,and provide an effective approach for the construction contradiction between shield sections and metro stations,and scheme of"shield first and then the station".