ISSN 1000-3665 CN 11-2202/P

    运营地铁盾构隧道基底沉降的影响因素分析

    Analysis on settlement factors of shield tunnel foundation for operating metro

    • 摘要: 隧道基底沉降不仅影响地铁列车的正常运行和乘客的舒适性,严重时会造成隧道结构病害,目前的研究主要集中在长期沉降预测和单因素影响分析,非常有必要开展隧道基底沉降的多影响因素分析。以郑州地铁1号线某盾构隧道区间为工程实例,构建三维有限元数值模型,采用人工激振力模拟地铁列车竖向荷载,提取数值模拟结果的动应力和静偏应力数据,引入循环荷载作用下累积塑性应变计算公式,采用分层总和法计算得到隧道基底沉降,研究了隧道周围土层性质、道床脱空深度和地铁列车运行速度等因素对隧道基底沉降的影响,研究结果表明:数值模拟的隧道基底沉降和发展规律与现场实测结果具有较高的吻合度,验证了有限元模拟的准确性;隧道基底沉降随着周围土层砂粒含量的提高而减小;道床脱空尺寸会加剧隧道和道床板中应力集中和振动放大现象,增大隧道下卧土层的动偏应力和基底沉降;提高车速会增大基底沉降的横向影响范围;采用正交试验法、极差分析法和方差分析法得到了隧道沉降对各因素的敏感性,从大到小依次为:土层性质、车速和道床脱空,其中,土层性质为高度显著水平、车速为显著水平。研究成果对运营地铁盾构隧道的变形监测、安全评估和加固处理具有一定的参考价值。

       

      Abstract: The metro tunnel settlement would directly affect the normal train operation and the comfort of passengers; severe uneven settlement can easily cause tunnel structural diseases. The relevant studies mainly focused on long-term settlement prediction and single factor impact analysis; it is necessary to analyze the multiple factors that influence the tunnel foundation settlement. A three-dimensional finite element numerical model of one shield tunnel section of Zhengzhou metro 1st line was constructed and the vertical load of metro train was simulated as artificial excitation force to extract the dynamic stress and static deviator stress data. Introducing the cumulative plastic strain calculation formula under cyclic load, the layered summation method was used to calculate the tunnel foundation settlement. The influences of factors, such as the properties of soil where the tunnel is buried, the depth of track bed void, and metro operation velocity, on the tunnel foundation settlement were further analyzed. The results show that the numerical simulated foundation settlement and development law are consistent with on-site measured results, which verifies the accuracy of finite element simulation. The tunnel foundation settlement decreases with the increase of sand content in the surrounding soil layer; the size of the track bed void would exacerbate the stress concentration and vibration amplification in the tunnel and track bed slab, and then increase the dynamic deviatoric stress of soil layer under the tunnel and foundation settlement. Increasing the metro train velocity would increase the lateral influence range of foundation settlement. The sensitivity of tunnel settlement to various factors is obtained with orthogonal experimental method, range analysis method, and variance analysis method. The descending order of sensitivity is soil layer properties, train velocity, and track bed void, in which, soil layer property has a highly significant level and vehicle speed a has significant level. This study can provide basic information for the deformation monitoring, safety assessment, and reinforcement treatment of operating metro tunnels.

       

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