薛彦琪, 张可能, 胡晓军. 2016: 深基坑开挖卸荷对下卧既有地铁隧道的影响分析. 工程地质学报, 24(6): 1230-1239. DOI: 10.13544/j.cnki.jeg.2016.06.024
    引用本文: 薛彦琪, 张可能, 胡晓军. 2016: 深基坑开挖卸荷对下卧既有地铁隧道的影响分析. 工程地质学报, 24(6): 1230-1239. DOI: 10.13544/j.cnki.jeg.2016.06.024
    XUE Yanqi, ZHANG Keneng, HU Xiaojun. 2016: ANALYSIS OF THE EFFECT OF DEEP FOUNDATION PIT EXCAVATION ON UNDERLYING METRO TUNNELS. JOURNAL OF ENGINEERING GEOLOGY, 24(6): 1230-1239. DOI: 10.13544/j.cnki.jeg.2016.06.024
    Citation: XUE Yanqi, ZHANG Keneng, HU Xiaojun. 2016: ANALYSIS OF THE EFFECT OF DEEP FOUNDATION PIT EXCAVATION ON UNDERLYING METRO TUNNELS. JOURNAL OF ENGINEERING GEOLOGY, 24(6): 1230-1239. DOI: 10.13544/j.cnki.jeg.2016.06.024

    深基坑开挖卸荷对下卧既有地铁隧道的影响分析

    ANALYSIS OF THE EFFECT OF DEEP FOUNDATION PIT EXCAVATION ON UNDERLYING METRO TUNNELS

    • 摘要: 长沙田汉大剧院地下空间商业项目一期基坑工程位于地铁1号线某区段正上方,坑底距隧道顶的最小距离约为6.2m。基坑坑底位于圆砾层中,地下水较丰富,考虑到降水对周边环境的影响,基坑工程采用封闭式止水帷幕并设置抗浮锚索。基坑开挖、降水引起的土体卸荷、地下水渗流,以及施工的抗浮锚索,共同影响坑底土体回弹,从而对下卧地铁隧道产生影响,如何分析与计算其影响成为该项工程的重点和难点。为此先通过两种常用的回弹变形估算方法计算坑底回弹量和隧道隆起位移;然后利用MIDAS GTS有限元软件建立三维数值分析模型,分别进行3种工况的模拟,包括不考虑地下水渗流影响并不采用抗浮锚索工况,考虑应力渗流耦合但不采用抗浮锚索工况,考虑应力渗流耦合并采用抗浮锚索工况。对比分析表明:帷幕渗透率较低时,考虑应力渗流耦合与不考虑渗流影响的坑底回弹和隧道隆起位移模拟结果基本一致;规范推荐估算方法在合理修正其卸荷应力,并确定合理的卸荷影响深度后,其计算结果与数值模拟结果相近。所得成果可为优化设计和施工提供有益的参考,并为类似工程提供借鉴。

       

      Abstract: The foundation pit project of Tianhan Grand Theatre's underground commercial construction is located above Line 1 of Changsha Metro and the minimum distance between the pit's bottom and the tunnel's roof is about 6.2m. The pit's bottom is situated in the round gravel layer in which the groundwater is rather abundant. Considering the impacts of dewatering on the surrounding environment, the enclosed water-resisting curtain combined with anti-floating anchor wires was applied to this project. The influence factors of the bottom soil resilience include soil unloading induced by the excavation and dewatering, the groundwater seepage and the application of anti-floating anchor cable. Thus, how to calculate and analyze the impact on underlying metro tunnels becomes the emphasis and difficulty in this project. Two common methods for estimating the spring back deformation were used to calculate the bottom's resilience value and tunnel uplift displacement. Then, the finite element software MIDAS GTS was employed to established a three-dimensional numerical model to simulate three types of engineering conditions. Case 1 took no account of the effect of groundwater seepage and didn't adopt anti-floating anchor wires. Case 2 considered the coupling of seepage and stress but didn't adopt anti-floating anchor wires. Case 3 considered not only the coupling of seepage and stress but the effect of anti-floating anchor wires. The comparative result shows that when the curtain has a lower permeability, the simulation result tends to be uniform regardless the influence of the coupling of seepage and stress. Besides, the calculating result of actual criterion is close to the simulation result, after amending the value and reasonable influence depth of unloading stress. The results can provide a beneficial reference for the design and construction of the similar projects to some extent.

       

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