考虑隧道掘进过程的新建隧道下穿既有隧道力学响应研究

Mechanical Responses of New Tunnel Down-crossing Existing Tunnel Considering Tunnelling Process

为有效评估新建隧道下穿施工对既有隧道的影响,确保既有隧道运营安全,将既有隧道简化为放置在Pasternak地基模型上的Euler-Bernoulli梁,基于两阶段分析法提出新建隧道下穿施工引起既有隧道力学响应的计算方法。通过与现场监测和既有方法的结果进行对比,验证了本文方法的准确性。研究结果表明:当新建隧道开挖面位于既有隧道中点时,既有隧道差异沉降达到最大值,转角曲线关于既有隧道中心线对称;在新建隧道掘进过程中,既有隧道的最大正弯矩和最大负弯矩分别出现在既有隧道长度的2/5和3/5位置附近,最大负剪力出现在既有隧道中点处;当新建隧道开挖面到达既有隧道长度的1/4和3/4位置时既有隧道产生最大正剪力;随着隧道轴线夹角和相对弯曲刚度增大,既有隧道的内力显著增大;增大隧道竖向净距有利于控制既有隧道的力学响应。本文方法考虑了新建隧道掘进过程和新建隧道与既有隧道的不同相对位置,可为类似穿越工程风险防控提供理论依据。

To effectively assess the influences of new tunnel down-crossing the existing tunnel and ensure the operation safety of the existing tunnel,the existing tunnel is simplified as a Euler-Bernoulli beam resting on the Pasternak model.A calculation method is presented to predict the mechanical responses of the existing tunnel induced by the new tunnel based on the two-stage analysis method.The accuracy of the proposed method is verified through comparisons of the results from field monitoring and existing methods.The results indicate that when the new tunnel face is located at the middle of the existing tunnel,the differential settlement of the existing tunnel reaches the maximum,and the rotation angle curve is symmetric with respect to the existing tunnel centerline.The maximum positive and negative bending moments occur at about 2/5 and 3/5 of the length of the existing tunnel respectively,while the maximum negative shear force occurs at the middle of the existing tunnel during new tunnel excavation.The maximum positive shear forces are produced when the new tunnel face arrives at 1/4 and 3/4 of the length of the existing tunnel.With the increases of the alignment angle and the relative bending stiffness,the internal forces of the existing tunnel significantly increase.Increasing the vertical clearance is conducive to controlling the mechanical responses of the existing tunnel.The proposed method takes into account of the tunnelling process and the different relative positions between the new tunnel and the existing tunnel,which can provide a theoretical basis for the risk prevention and control of similar crossing projects.