摘要
采用MIDAS有限元软件,模拟两隧道间距为 2.76、4.76、6.76 m时,新建铁路隧道上穿既有隧道的施工过程,对比分析既有隧道的位移和应力变化情况,并与现场监测数据对比验证.结果表明,3种不同间距下,随着新建隧道开挖,既有隧道竖向位移向上隆起,水平位移在两隧道交叉点前向左偏移,两隧道交叉点后向右偏移,既有隧道横断面竖向位移大于水平位移,既有隧道应力变化趋势以两隧道交叉点为界,先波动增长后波动递减,且最大拉应力位于既有隧道左边墙处;既有隧道位移与应力变化和两隧道间距呈反比,以两隧道间距 2.76 m为基准,间距每增加 2m,既有隧道最大竖向位移依次降低了 21%、36%,最大水平位移依次降低了 57%、53%,最大拉应力依次降低了 11%、21%;基于既有隧道位移结果,总结了不同间距下既有隧道关键部位的位移预测公式,且间距为 2.76 m时,既有隧道位移及围岩应力数值模拟结果均接近现场实测数据.
Abstract
The MIDAS finite element software was used to simulate the construction process of the new railway tunnel passing through the existing tunnel above when the spacing between the two tunnels was 2.76,4.76 and 6.76 m.The displacement and stress changes of the existing tunnel were compared and analyzed,and verified with the on-site monitoring data.Results show that under three different spacings,with the excavation of the new tunnel,the vertical displacement of the existing tunnel rises upward;the horizontal displacement is offset to the left in front of the intersection of the two tunnels,and to the right after the intersection of the two tun-nels;the vertical displacement of the cross-section of the existing tunnel is greater than the horizontal one;the stress change trend of the existing tunnel is bounded by the intersection of the two tunnels,with the fluctuation increasing first and then decreasing,and the maximum tensile stress is located at the left wall of the existing tunnel.The displacement and stress changes of the existing tunnels were inversely proportional to the spacing between the two tunnels:taking the spacing between the two tunnels as the benchmark,for each 2 m increase in the spacing,the maximum vertical displacement of the existing tunnels decreased by 21%and 36%,the maximum horizontal displacement decreased by 57%and 53%,and the maximum tensile stress decreased by 11%and 21%in turn.Based on the displacement results of existing tunnels,the displacement prediction for-mula of key parts of existing tunnels at different spacings was summarized,and the numerical simulation results of existing tunnel displacement and surrounding rock stress at a spacing of 2.76 m were close to the measured data on site.
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万方数据