上覆富水砂层地铁隧道掌子面变形特征数值试验研究
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张红军(1987—),男,高级工程师,博士(后)。主要从事重大地质灾害治理方面的研究。E-mail:sduhongjun@163.com

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TU443

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山东省自然科学基金项目(ZR2019BEE021)资助


Numerical Experimental Study on Deformation Characteristics of Metro Tunnel Excavation Surface with Overlying Water-rich Sand Layer
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    摘要:

    为研究地铁隧道在上覆富水砂层下的变形特征,以典型上覆富水砂层隧道—青岛地铁 2 号线啤—苗区间为工程研究背景,采用 FLAC 3D 数值模拟软件对不同富水砂层厚度与隔水层厚度工况下隧道掌子面位移、塑性区变化特征进行了研究分析。研究结果表明:隔水层厚度是影响掌子面是否发生涌水涌砂的主控因素,在开挖过程中应时刻注意富水砂层距离隧道顶板的安全距离,临界隔水层的厚度为 3 m。同时,当隔水层厚度越大、富水砂层厚度越小时,掌子面变形就会越小。以临界工况为研究对象,通过分析开挖过程中隧道拱顶—拱腰—掌子面应力和位移变形规律,引入了位移释放系数和应力释放率两参数来揭示围岩与掌子面在隧道开挖过程中的影响关系。通过进一步拟合掌子面失稳破坏预测方程,得到了掌子面变形释放率拐点先于同一断面围岩径向变形且发生在开挖到目标断面之前的重要结论,因此在实际隧道开挖过程中应将掌子面的变形作为首选敏感监测指标。研究结果可为该不良地质条件下隧道掌子面稳定性和预加固时机选择提供一定的理论指导。

    Abstract:

    In order to study the deformation characteristics of subway tunnel under the unfavorable geological conditions of overlying water-rich sand layer, a typical tunnel, in dynamic water-rich and weakened sand stratum of Qingdao metro No.2 line (the Pi-Miao section), was taken as a research model, FLAC3D numerical simulation software is used to study the displacement of tunnel excavation surface and the variation characteristics of plastic zone under different thickness of water-rich sand layer and water-repellent layer. The results show that the larger the thickness of the water-repellent layer and the smaller the thickness of flowing sand layer, the smaller the deformation of the excavation surface will be. The thickness of waterproof layer is the main control factor affecting whether water and sand inrush occurs on the excavation face. In the process of excavation, maintain a safe distance between the sand layer and the tunnel. Once it is less than 3 m, tunneling should be stopped immediately and corresponding advance reinforcement measures should be taken. Taking the critical condition as the research object, the stress and displacement deformation law of tunnel's arch, waist, and face during excavation were analyzed, and the displacement release coefficient and stress release rate were introduced to reveal the relationship between surrounding rock and the excavation face during tunnel excavation. By further fitting the prediction equation for the instability and failure of the excavation face, an important conclusion was drawn: that the inflection point of deformation release rate of excavation face is prior to the radial deformation of the surrounding rock in the same section and occurs before the excavation reaches the target section. Therefore, the deformation of the excavation face should be regarded as the primary sensitive monitoring index during the actual tunnel excavation. The research results can provide some theoretical guidance for the stability of the tunnel excavation face and the selection of pre-reinforcement timing under the unfavorable geological conditions.

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张红军,张太平,王奎峰,许艳,王薇,王强,张龚.上覆富水砂层地铁隧道掌子面变形特征数值试验研究[J].防灾减灾工程学报,2023,43(6):1454-1462

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  • 收稿日期:2022-10-09
  • 最后修改日期:2023-04-12
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  • 在线发布日期:2024-01-11
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