Numerical investigation on tunnel floor failures under high water pressure considering the effects of construction joints

Abstract Failures caused by groundwater on tunnel floors, such as floor heave, leakage, and cracking, have presented significant challenges for the safe operation of high‐speed railway (HSR) tunnels. One major but overlooked cause of these water‐related problems is concealed damage in the concrete construction joints of tunnel floors. This study conducts a refined numerical investigation based on a case of water‐related failures in an HSR tunnel floor. The study's innovation lies in its comprehensive consideration of the cracking and seepage process of the construction joints using the cohesive zone model and the fracture flow model specially developed to address this issue. The obtained results predict that the tunnel's original drainage system is ineffective in reducing the high external water pressure at the bottom of the tunnel, leading to floor heave. The damage at the construction joint interface primarily occurs as a result of floor heave and is mainly distributed at the invert arch‐invert fill interface and the invert fill‐leveling layer interface. This damage weakens the stiffness of the tunnel floor, making it easier for the track deformation to reach the operation warning value compared to the model that does not consider the interface effect. Pressurized groundwater can seep into the construction joints through areas with poor waterproofing, resulting in interlayer water pressure that uplifts the track structure before damage occurs at the entire invert arch–arch fill interface. Lastly, a new drainage system that combines an external bottom channel and interlayer drainage pipe was proposed according to the characteristics of the water‐induced failures, which can effectively prevent floor heave and joint leakage.