Analysis to gushing in Wuchiba tunnel and features of karstification

There are six types of karst physiognomy in Wuchiba and two karst water systems （with three underground rivers） relate to the tunnel. The Baiyanba subterranean stream is controlled by the types of carbonate rocks with simple conduit structure and featured hydrogeologically by being of lateral recharge and longitudinal discharge. The Longtang and Maotian subterranean streams are controlled by geologic structure and featured with multilevel conduit branch and discharge way. The Wuchiba highway tunnel is divided into three parts and five sections of karst zone by the author. Method of infiltration coefficient of precipitation, modulus method of groundwater runoff and analogy method of hydrogeology are adopted to calculate and forecast the rate of gushing water in each subsection. Then, the influence of karstification features in each subsection on gushing water is analyzed and concludes that the maximum rate of the tunnel attains to 31.3× 10^4m^3/d between ZK256＋300 to ZK257＋000 section.