Water Hazard Characteristics of Dabaoshan Atypical Karst Tunnel

To study the water hazard characteristics of DaBaoshan atypical karst tunnel. Engineering geological and hydrogeological mapping and survey, water connection test, tunnel water hazard investigation, theoretical calculation and analysis are used. The results show that the lithology of the DaBaoshan tunnel is argillaceous limestone, limestone, carbonaceous shale limestone, limestone and inferior coal seam, which is an atypical karst tunnel. There are three karst collapses, but there are not perennial water bodies on the surface of tunnel hill. In the rainy season, there are gushing water and mud in the tunnel, the water source of tunnel water hazard is rainfall, and the gushing water channels are surface collapse, dissolved crack and fissure. The calculation results show the rainfall intensity are 7.84mm/h, 8.44 mm/h, 9.18mm/h, 10.17 mm/h respectively, the rainfall time that lead to the gushing water exceeds the drainage capacity of the gutters are 2.5h, 2.2h, 2.0h, 1.8h respectively. And when the rainfall intensity is 33.3mm/h, the rainfall time is only 35min. The tunnel gushing water causes a lot of water, mud and sands flows on the road which endangers traffic safety, even causing traffic accidents.