近年来市政隧道工程蓬勃发展，许多城市公路隧道受建筑、管线等因素的限制，并为节约用地、缩短工期等，大多被设计成小净距隧道。小净距隧道在施工过程中与分离式隧道最显著的区别是中隔岩柱受力状态复杂、稳定性难以控制。通过理论推导对浅埋超小净距隧道土质中隔岩柱的失稳机理进行系统研究，基于小净距隧道中隔岩柱承载模型确定中隔岩柱上覆应力，结合土体极限应力公式对中隔岩柱在不同施工条件下的失稳破坏特征进行分析。研究结果表明，增大土体的黏聚力、内摩擦角及支护反力均能提高土体的极限应力，且增加支护反力效果更显著。

Municipal tunnel engineering has developed vigorously in recent years, but many urban highway tunnels’ development are limited by construction, pipeline and other factors. In order to save land and construction period, most of them are designed as neighborhood tunnels. The most significant difference between neighborhood tunnel and separated tunnel during the construction process is that the stress state of the mid-adjacent rock is complex and the it’s stability is difficult to control. By the theoretical derivation, the instability mechanism of the soil mid-adjacent rock in shallow neighborhood tunnel is studied. Based on the bearing model of the neighborhood tunnel’s mid-adjacent rock the overburden pressure of mid-adjacent is ascertained. Combining the ultimate stress formula of the soil, the instability and failure characteristics of mid-adjacent road under different construction conditions are analyzed. Increasing the cohesion, internal friction angle and support reaction force can increase the ultimate stress of the soil, what’s more, the effect of increasing the support reaction force is more significant. Provide theoretical support for the role of supporting structure.

TU457;U456.3