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
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.
Central Yunnan Water Diversion Projectextra-long tunnelKarstwater inrushrisk assessment
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