Abstract: To solve the problems of mud and water gushing and tunnel collapse caused by unfavorable geologies such as karst cave, karst pipeline, and underground river during tunnel construction, and ensure the safety of tunnel construction and operation, comprehensive countermeasures of beam plate crossing, sealing out of tunnel and drainage in tunnel, and support strengthening are adopted on the basis of kast cave conditions revealed and geological evaluation results. The box beam structure is adopted to cross karst cave, and drainage facilities are introduced by taking the karst treatment of Xiaosanxia tunnel of ZhengzhouWanzhou highspeed railway as an example. The field practical results show the following. (1) The beam span structure is feasible in karst fissure and karst cave damage section, which can provide a solid foundation. (2) The surface river paving measures and the drainage channel laid in the karst cave area of the tunnel can effectively reduce the surface water infiltration. (3) The drainage channel is designed to drain the highpressure water in tunnel bottom, thus reducing the rail uplift risk of tunnel.

Key words: karst tunnel, karst cave, beam plate crossing, river pavement, drainage channel, comprehensive treatment