Prediction and prevention of sudden water gushing in the Hongtuzhang tunnel

Prediction of hydrogeological conditions in front of the palm face in the construction of deep-buried tunnels under complex geological conditions is extremely critical to ensuring the construction safety. Previous works in the study site revealed that the traditional investigation methods cannot describe the geological and hydrogeological characteristics very well and have big deviation from the realities, causing unpredicted tunnel water inrush during the construction. To better predict the geological and hydrogeologic situation in the deep-buried tunnel and determine the possible flood water inrush area, we applied the controllable source audio magnetotelluric method in the Hongtuzhang tunnel construction in Gongdong province. The results show that this new method can better determine the true geological and hydrogeologic condition in the deep-buried tunnel, and match the actual excavation results. Especially this method predicted a potential gushing water inrush point, which was proved to have a maximum gushing water amount of 2 300 m³/h. Based on this detailed founding, we used the advance curtain grouting method to effectively seal the corresponding fault, which limits the water outflow and makes the excavation process in safe. Application of this method is a good test example for the prediction of tunnel water gushing, and can provide a better technology backup for the prevention of related geologic hazard.