Hydro-mechanical Coupling Response Behaviors in Tunnel Subjected to a Water-Filled Karst Cave

Tunnel construction usually suffers some water-filled karst caves, which can change the stress and flow fields and bring about unpredictable engineering disasters. A typical form of water inrush disaster caused by combination of steep karst fissures and concealed karst cave is proposed in this paper. The mechanism of this water inrush disaster is studied from aspects of geology and hydro-mechanical coupling response behaviors of surrounding rock. Geological conditions including lithology, attitude of rock formation, supply and runoff conditions, climatic characteristics, etc. of Qiyueshan (QYS) tunnel are analyzed to figure out causes of this disaster. A geological conceptual model is established to describe the causes from geological aspect. Then a numerical model is built through simplifying the geological conceptual model to simulate and study hydro-mechanical coupling response behaviors of tunnel surrounding rock on the platform of PANDAS software. In addition, effects of position and size of the karst cave, and distance between the tunnel and the karst cave on principal stress and displacement of surrounding rock are discussed, which can be used to predict position, size and distance of karst caves in actual engineering.