Karst hydrogeology and risk assessment of the Huali tunnel

The Huali tunnel on the Wengan-Kaiyang railway is a key engineering site, which is complicated by sinkholes, shafts, karst springs，and underground rivers. In this work, the lithologic combination of aquifers, distribution of soluble rock mass and karst water of this karst tunnel are studied by geological investigation, borehole drilling, field measurement, laboratory tests of physical and mechanical parameters and electrical geophysical prospecting. Results show that， (1) The karst groundwater system in the tunnel area can be divided into two hydrogeological units， a non-soluble rock system composed of argillaceous siltstone and a soluble rock system composed of limestone．(2) The normal tunnel water inflow is predicted to be 32，126.4 m3· d-1，and the maximum gushing water amount in the rainy season should be designed as 2 to 6 times of that in the normal condition．(3) The overall risk of karst water gushing is moderate, while the section with extremely high risk accounts for 16% of the total length.