穿越复杂岩溶环境的特长隧洞涌突水危险性评价——以滇中引水工程小扑隧洞为例

Risk assessment of water inrush in an extra-long tunnel through a complex Karst area—A case study of Xiaopu Tunnel in the Central Yunnan Water Diversion Project

在复杂岩溶区,涌突水危险性评价是保障隧洞施工安全的重要工作内容之一。以滇中引水工程玉溪红河段小扑隧洞为例,在分析隧洞地质与水文地质条件的基础上,综合考虑岩石的可溶性、地质构造因素、地表汇水条件、地下水化学特征、隧洞埋深与地下水位的关系5个控制性因素,采用岩溶隧洞涌突水危险性评价系统对隧洞的涌突水危险性进行了预测与验证。结果表明:小扑隧洞北段位于鲁纳寺—牛恋村岩溶子系统的径流区。在丰水期,隧洞岩溶涌突水中危险区、高危险区、极高危险区的长度占比分别为15.8%,55.4%,28.8%。小扑隧洞南段位于西河和祭天山—黄营岩溶子系统的补给、径流区。在丰水期,隧洞涌突水中危险区、高危险区、极高危险区的长度占比分别为7.4%,52.7%,39.9%。施工阶段,小扑隧洞北段主洞揭露暗河管道,发生涌突水事故,2#支洞发生突水涌沙事故,与对应的涌突水高-极高危险性结果吻合。涌突水危险性评价结果有效地支撑了隧洞的涌突水灾害防治与安全施工。

Assessing the risk of water inrush is an important means of ensuring the safe construction of tunnels in complex Karst areas.This study assesses the risk of water inrush in the Xiaopu Tunnel,which is located in the Yuxi-Honghe section of the Central Yunnan Water Diversion Project.We first analyzed the geology and hydrogeological setting of the area.We then considered five key factors—the solubility of rocks,geological tectonic features,characteristics of the catchment of surface water,chemical characteristics of groundwater,and the relationship between the tunnel and groundwater level—to develop a system to assess the risk of water inrush into the Karst tunnels.The results showed that the northern section of the Xiaopu Tunnel was located in the runoff zone of the Lu’nasi-Niuliancun Karst subunit.The ratios of length of medium,high,and extremely high risks of water inrush in this section accounted for 15.8%,55.4%,and 28.8%in the rainy season,respectively.The southern section of the Xiaopu Tunnel was located in the recharge and runoff zone of the Xihe and Jitianshan-Huangying Karst subunits.The ratios of length of medium,high,and extremely high risks of water inrush in this section accounted for 7.4%,52.7%,and 39.9%in the rainy season,respectively.Branches of tunnels 1#and 2#in the northern section exposed the subsurface river,and were subjected to inrushing water during construction,where this is consistent with the results of prediction of high to extremely high risk of water inrush in this section.The results of assessment of the risk of water inrush can support measures for the prevention and control of inrushing water to ensure the safe construction of tunnels.