Mud Inrush Hazard in Tunnel Excavation and its Prediction

Water and mud inrush will cause severe security risk and great economic loss to tunnel construction, it will also cause unrecoverable damage to relevant environment. However, the prediction and prevention still remain as a very difficult problem. In contrast, mud inrush is more harmful, but on which research work is far from adequate. According to geological survey, Lingjiao tunnel is judged to be safe from danger of large-scale water and mud inrush. Unfortunately, a large mud outburst accident happened with bursting mud of more than 40,000 m3, leaving a huge collapse pit on the upper surface of the crossed mountain. Moreover, another mud inrush took place right in the paralleling tunnel nearby one year after the first accident, which triggered another follow-up collapse in the same site as the first time, though it has been reinforced with concrete cover. Facts above show that the two-track tunnel crossed the same mud-filled structure, which was not well-understood. In this study, the mud-inrush process, causes and treatment measures are expatiated. Through case study, we hope to provide reference for prediction and prevention of mud-inrush disaster during tunnel construction in the future.