针对厦门地铁1号线莲坂站~莲花路口站盾构区间隧道工程,通过现场监测和数值模拟,研究在上软下硬地层中过渡区盾构法隧道施工对地表沉降变形规律的影响.研究结果表明:上软下硬地层地表横向沉降受硬层比的影响比较明显,基本上表现为随硬层比增大,地表沉降量整体减小且沉降槽变浅的趋势.其中隧道轴线正上方以及轴线附近监测点的沉降量受硬层比的影响相对于远离隧道轴线的监测点要大;上软下硬地层地表纵向沉降受硬层比的影响主要表现在地表纵向沉降量及开始和结束的位置变化上,随着硬层比的变大,盾构施工对地表纵向沉降量及其影响范围都在缩小;通过研究隧道轴线正上方监测点地表最终沉降值与硬层比的关系,建议将硬层比15%~85%视为开展上软下硬地层地表变形研究的阈值.%In view of the shield tunnel project of the Xiamen metro line 1 from Lianban Station to Lianhua Road station, the surface subsidence caused by shield construction in the upper-soft and lower-hard ground was investigated, through the statistical analysis of field monitoring data during the process of construction and the numerical simulation using finite difference method. Research shows that: the transverse surface settlement pattern of upper-soft and lower-hard ground is under substantial influence of the hard layer ratio, and the general trend is that with a higher ratio the overall surface settlement becomes less and the settlement trough becomes shallower. In particular, the settlement of the observations points directly above or close to the tunnel axis are more influenced by this ratio than those far away from the axis. The influence of the hard layer ratio on longitudinal surface settlement pattern of upper-soft and lower-hard ground is mostly reflected by the start and end locations of longitudinal surface settlement, and as this ratio grows the shielding work has an influence on surface settlement over a smaller area. A study of the final settlement--hard layer ratio relationship involving observation points directly above the tunnel axis suggests that hard layer ratio of 15%~85% be adopted as the threshold values in upper-soft and lower-hard ground surface deformation research.
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