Analysis on characteristics of karst water gushing under tunnel spatial distribution in ejective fold structure area of southeast Sichuan

Currently the study of tunnel water bursting in ejective fold structure area is confined to a specific tunnel engineering and corresponding karst water system. It is lack of systematic study of water gushing problem under tunnel spatial distribution. In this paper, the characteristics of karst water runoff under tunnel spatial distribution is summarized and divided into seven categories according to the difference in horizontal and vertical zoning of karst water. The spatial characteristics of karst water bearing media, differences in karst development and the features of karst water flow in the region have been analyzed. Accordingly, the types and features of karst water gushing were comparatively discussed. This paper also presents typical examples (Tongluoshan and Mingyueshan tunnels of proposed Chongqing-Wanzhou Passenger Line), which analyses the characteristic of the tunnel karst water and associated result show that Tongluoshan tunnel is identified as type one and Mingyueshan tunnel as type four. Combining with the differences in karst development, encountering water inrush is analysed by qualitative evaluation and calculation. Therefore, Tongluoshan tunnel will have a small amount of water gushing occurring only during rainy season, which will be controlled by rainfall intensity, whereas Mingyueshan tunnel will have a larger amount of gushing water.