重载列车荷载作用下穿越不同地层位置的隧道动力响应分析

Dynamic Response Analysis of Tunnels through Different Stratum Positions under Heavy-duty Train Load

当隧道穿越不同地层位置时,岩土体的性质对隧道结构稳定性的影响不能忽略。以某既有隧道为研究背景,通过激振力函数得到重载列车激振荷载,运用有限差分软件建立三维模型进行数值模拟,选取Ⅲ级围岩、Ⅳ级围岩、Ⅴ级围岩这三种典型工况,研究重载列车隧道的动力响应。发现随着围岩条件的恶化,隧道底部加速度、拱顶竖直位移以及仰拱衬砌处的最大、最小主应力峰值均随之增大。在同一工况下,加速度响应的总体趋势不尽相同,均为隧道底部加速度>拱脚加速度>拱腰加速度>拱顶加速度;竖直位移响应总体趋势为下部大于上部,即隧底竖直位移>拱脚竖直位移>拱腰竖直位移>拱顶竖直位移;仰拱衬砌处的最大、最小主应力响应规律基本一致。总之,重载列车穿越不同地层位置时,最不利位置主要发生在隧底和拱顶处,因而越是恶劣的围岩条件,越是应该将不利位置作为维修加固的重点予以关注。

When the tunnel traverses different stratum positions,the influence of the nature of rock and soil on the stability of the tunnel structure cannot be ignored.Taking an existing tunnel as the research background,this paper obtains the excitation load of the heavy-duty train through the excitation force function,uses finite difference software to establish a three-dimensional model for numerical simulation,and selects grade III surrounding rock,grade IV surrounding rock,and grade V surrounding rock.Three typical working conditions are used to study the dynamic response of heavy-duty train tunnels.It is found that as the surrounding rock conditions deteriorate,the acceleration at the bottom of the tunnel,the vertical displacement of the vault,and the maximum and minimum principal stress peaks at the invert lining all increase accordingly.Under the same working conditions,the overall trend of acceleration response is different,all are tunnel bottom acceleration>arch toe acceleration>arch waist acceleration>vault acceleration;the overall trend of vertical displacement response is that the lower part is larger than the upper part,that is,the vertical displacement of the tunnel bottom>vertical displacement of arch foot>vertical displacement of arch waist>vertical displacement of vault;the maximum and minimum principal stress response law of the invert lining is basically the same.In short,when heavy-duty trains pass through different stratum positions,the most unfavorable positions mainly occur at the bottom of the tunnel and the vault.Therefore,the worse the surrounding rock conditions are,the more disadvantaged positions should be paid attention to as the focus of maintenance and reinforcement.