Stability Analysis and Evaluation of a Tunnel Entrance Slope Under Complex Disaster-Prone Environments
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摘要:
高地震烈度、高地应力、高陡、高寒等复杂孕灾环境下的隧道洞口斜坡，在降雨、强震或人类强烈工程活动影响下，极易发生崩塌、滑坡、泥石流等地质灾害. 为探究复杂孕灾环境下隧道进口斜坡在不同工况条件下的稳定性，以我国西南某加日山隧道为依托，通过无人机摄影、槽探、室内实验及洞探原位测试等“天空地”一体化勘察技术，实现斜坡工程地质信息精细获取，系统揭示斜坡典型破坏特征，讨论斜坡2种破坏成因与演化模式，在此基础上，利用极限平衡法与三维数值模拟方法，量化分析不同工况下的斜坡稳定性. 研究结果表明：加日山隧道进口斜坡在自然工况、暴雨工况、地震工况3种工况下稳定性系数均大于1.15，斜坡整体处于稳定状态，仅后缘表部存在局部变形失稳的可能，成果可为类似隧道的选线规划以及建设运营安全提供理论指导和技术支撑.
Abstract:Influenced by rainfall, strong earthquakes, and intensive engineering activities, the slope at the tunnel entrance may experience collapses, landslides, debris flows, and other geological disasters, especially under the complex conditions of violent earthquakes, high geostress, abrupt slopes, and extremely cold environments. To explore the stability of tunnel entrance slopes under different working conditions in complex disaster-prone environments, the Jiarishan tunnel in southwest China was taken as an example, and a “space-air-ground” integrated investigation technology combining unmanned aerial vehicle (UAV) photography, surface trenching, laboratory experiments, field tests, and cave surveys was employed to obtain accurate engineering geological information. Typical failure characteristics of the studied slope were systematically revealed, and the two failure causes and evolution models of the slope were discussed. In addition, the slope stability under different working conditions was qualitatively analyzed using the limit equilibrium method and three-dimensional numerical simulation. The results indicate that the stability factor of the slope at the Jiarishan tunnel entrance is always greater than 1.15 under natural, rainstorm, and earthquake working conditions. Overall, the slope is stable except for the local deformation and instability of the shallow horizon of the posterior margin. This research can provide theoretical guidance and technical support for similar tunnels in terms of siting, construction, and operation safety.
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Key words:
- disaster-prone environment /
- slope deformation /
- evolution mode /
- stability analysis
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图 1 石林、石墙、石丛地貌及石墙走向
Figure 1. Morphologies of stone forest, stone wall, stone cluster, and direction of stone wall
图 3 多手段获取的斜坡岩体卸荷特征
Figure 3. Unloading characteristics of slope obtained using various methods
图 4 坡面小型溶洞沿构造线分布示意
Figure 4. Distribution of small caves of slope along structural lines
图 7 某隧道进口斜坡推测潜在失稳模式
Figure 7. Potential instability patterns of slope at tunnel entrance
表 1 斜坡岩体力学参数建议值
Table 1. Suggested mechanical parameters of slope rock masses
岩体质量等级 干密度 ρd/（g·cm−3） 变形模量 E0/GPa 泊松比 μ 抗剪断强度 摩擦系数 黏聚力/MPa Ⅱ 类 2.52～2.58 (10, 20] [0.25, 0.29] (1.20, 1.40] (1.50～2.00] Ⅲ 类 2.30～2.50 (5, 10] (0.29, 0.33] (0.80, 1.20] (0.70～1.50] Ⅳ 类 2.10～2.40 [2, 5) (0.33, 0.37] [0.55, 0.80] [0.30～0.70] 
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表 2 结构面强度试验成果
Table 2. Test results of structural surface strength
试验编号 试验位置/m 抗剪断强度 抗剪强度 地质特征 摩擦系数 黏聚力/MPa 摩擦系数 黏聚力/MPa 1-1 PDG01 洞 0+150 m 1.09 1.33 0.87 0.20 主要为压碎带弱风化大理岩，但剪切主要沿压碎带及其影响带剪断 1-2 PDG01 洞 0+71 m 0.81 1.34 0.70 0.51 弱风化大理岩，碎裂结构，岩级为 Ⅳ 岩体
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