水蚀影响下大跨钙积黄土隧道开挖稳定性分析

钙积黄土隧道施工过程力学响应复杂,以周山隧道为例,通过对场址周围地质特征分析,明确隧道灾害机制,并提出考虑水蚀软化影响的围岩压力计算方法,进一步通过数值模拟探究不同开挖方式对钙积黄土隧道稳定性影响规律。研究结果表明:(1)钙积黄土水蚀软化作用明显,隧道开挖需格外重视水对隧道稳定性的影响;(2)考虑钙积黄土浸水软化的围岩压力计算简化模型,计算参数选取简便,可用于隧道开挖稳定性的理论计算;(3)在钙积黄土发育地段,建议根据地质和水文条件对CRD与CD等工法进行比选,当地层含水率ω>25%时,宜采用CRD法施工。

Excavation Stability Analysis of Long Span Calcareous Cemented Loess Tunnel under Water Erosion

The mechanical characteristics of calcium loess tunnel construction process is complex. Taking Zhoushan tunnel as an example, through the analysis of the geological characteristics around the site, the tunnel disaster mechanism is clarified, and the surrounding rock pressure calculation method considering the influence of water erosion softening is proposed, and the influence law of different excavation methods on the stability of calcareous loess tunnel is further explored through numerical simulation. The results show that: (1) The calcareous nodule loess is obviously softened by water erosion, so the influence of water on tunnel stability should be paid more attention to in tunnel excavation. (2) The simplified calculation model of surrounding rock pressure considering the water immersion softening of calcareous cemented loess is easy to select, which can be used for theoretical calculation of tunnel excavation stability. (3) In the section where calcareous nodule loess is developed, it is suggested to compare and select CRD and CD construction methods according to geological and hydrological conditions. When the water content of local stratum is more than 25%, CRD method should be used.