隐覆溶洞对地铁盾构隧道稳定性影响的数值分析

为研究岩溶区隐覆溶洞对盾构地铁隧道区间稳定性的影响，依托位于高原岩溶发育区昆明轨道交通4号线联大街站—吴家营站区间盾构地铁隧道工程，应用物探钻孔法和电磁波CT法勘探盾构地铁隧道区间的溶洞分布； 采用三维有限元数值分析方法，分别研究盾构隧道不同埋深时隧道下侧溶洞对隧道稳定性的影响，以及隧道周边溶洞半径、溶洞填充状态、溶洞位置、溶洞隧道间距对盾构隧道开挖稳定性的影响，分析岩溶发育区盾构法地铁隧道施工过程中隧道结构的稳定性。研究结果表明： 1）综合应用钻孔法和电磁波CT法，可较好地判断岩溶强发育区内的溶洞分布； 2）当隧道周边溶洞尺寸和位置不变时，盾构隧道围岩塑性区和变形量随溶洞埋深的增大而增大； 3）当隧道周边溶洞半径增大时，溶洞与隧道围岩间的应力集中区域变得分散，盾构隧道围岩变形量减小； 4）隧道周边溶洞内填充物及数量对盾构隧道围岩的变形量基本没有影响； 5）隧道周边溶洞位置对盾构隧道围岩变形的影响程度分别为盾构隧道围岩左、右侧的溶洞大于盾构隧道围岩下侧的溶洞，盾构隧道围岩下侧的溶洞大于盾构隧道围岩上侧的溶洞； 6）隧道周边溶洞仅在距隧道一定范围内才对盾构隧道施工稳定性有较大影响。

Numerical Analysis on Influence of Concealed KarstCaverns upon Stability of Metro Shield Tunnel

To study the influence of concealed karst caverns on the stability of metro shield tunnel, the karst caverns distribution of a metro shield tunnel on Lianda Street Station Wujiaying Station of Kunming Rail Transit Line 4 located in the plateau karst Development area are explored using borehole geophysical prospecting and electromagnetic CT methods. The three dimensional finite element numerical simulation method is adopted to study the influence of lower karst caverns on stability of shield tunnel with different burial depths and that of karst cavern radius, state of karst cavern filling, position of karst cavern and spacing between karst cavern and tunnel on the stability of shield tunnel. Then the stability of tunnel structure in karst development area during construction process is analyzed as well. The results show following. (1) The karst caverns distribution can be well explored using borehole geophysical prospecting and electromagnetic CT methods. (2) When the size and position of the karst cavern remain unchanged, the plastic zone and deformation of the surrounding rock of the shield tunnel increase with the increasing burial depth of karst cavern. (3) With the increase of karst cavern radius, the stress concentrated area between tunnel and karst cavern becomes dispersed, and the deformation of tunnel surrounding rock decreases. (4) The materials and amount of filler in the karst cavern has no effect on the deformation of surrounding rock of tunnel. (5) The influence degree of karst cavern at the both sides of tunnel on the deformation of tunnel surrounding rock is greater than that of karst cavern below tunnel, and that of karst cavern below tunnel is greater than that of karst cavern above tunnel. (6) The karst cavern would affect the tunnel construction within a certain spacing between tunnel and karst cavern.