Research conclusions: Properly different treatments shall be adopted according to different conditions because the development of karst is complicated and changeable. When the depth of filling material is unknown, expanding the excavation area to provide enough space and freedom degrees for the detection and structural disposal is appropriate. When the tunnel passes through groundwater circulation zones and the draining base-level is deeper (many deep ravines in the section), the impact of groundwater shall be ignored. The karst cave shall be treated as dry one, but the drainage channels should be reserved for avoiding the groundwater flooding the cave. More security coefficient should be remained for the impact force and other uncertain factors affecting the structural foundation with dynamic and static framework by train passing through.