浅埋黄土隧道塌方破坏模式及处置技术

以宁夏某浅埋黄土隧道塌方事故为依托，首先讨论分析浅埋黄土隧道的塌方破坏机理及模式，然后根据现场塌方情况，分析案例隧道塌方原因并提出处置方案，最后通过数值模拟和现场监测对其处置效果进行评价。结果表明：黄土自身的易灾性、不良地形地势、浅埋隧道施工扰动以及强降雨入渗共同导致隧道上方围岩形成一定范围的黄土软弱湿陷带，原隧道支护结构无法抵抗劣化后的围岩，围岩变形和结构受力均大幅增加，其中拱顶沉降增大了91.8%,拱肩处初支正弯矩增大了60.7%;黄土地层开挖面失稳破坏可分为掌子面到达软弱湿陷带的失稳破坏和穿越整个软弱湿陷带的失稳破坏两种模式；结合有限元模拟和现场监测验证，“临时支护系统+换拱+超前中管棚注浆加固”的综合防塌方处置技术应用效果显著。

Failure Mode and Treatment Technology of Shallow Buried Loess Tunnel Collapse

Based on the collapse accident of a shallow buried loess tunnel in Ningxia, this paper first discusses and analyzes the collapse failure mechanism and mode of the shallow buried loess tunnel. Then, based on the on-site collapse situation, the causes of the tunnel collapse are analyzed and the disposal plans are proposed. Finally, the disposal effect is evaluated through numerical simulations and on-site monitoring. The results show that the vulnerability of loess itself, adverse terrain, disturbance du-ring shallow tunnel construction, and heavy rainfall infiltration jointly lead to the formation of a certain range of loess soft and collapsible zones in the surrounding rock above the tunnel. The original tunnel support structure cannot resist the degraded surrounding rock, and the deformation and structural stress of the surrounding rock increase significantly. Among them, the settlement of the arch crown increases by 91.8%, and the initial positive bending moment at the arch shoulder increases by 60.7%; The instability and failure of the excavation face in loess strata can be divided into two modes: the instability and failure of the palm face reaching the weak and collapsible zone, and the instability and failure of crossing the entire weak and collapsible zone. Combining the finite element simulation and on-site monitoring verification, the comprehensive anti-collapse treatment technology of "temporary support system plus arch replacement plus advanced pipe shed grouting reinforcement" has shown significant application effects.