The influence of tunnel floor heave induced by high water pressure on the mechanical response of ballastless track

Tunnels in complex geological and high water pressure environments are prone to diseases such as tunnel floor heave (TFH), which seriously affects the operation and safety of high-speed railways. Water is a key contributing factor to TFH. By applying radial loads and constraint conditions to the tunnel base, the confining pressure effect caused by high water pressure and water-induced mudstone swelling on the tunnel base is simulated, and a tunnel base structure-load model is established. Furthermore, a refined finite element simulation analysis model considering the cohesive zone model and concrete damage plastic is developed to study the influences of different confining pressures, confining pressure ranges, and inverted arch thicknesses on the deformation, interlayer bonding, and interlayer gap of the track structure. The calculation results indicate that the maximum vertical deformation of the rail is positively correlated with the confining pressure and negatively correlated with the inverted arch thickness. The deformation range is closely related to the confining pressure range. The deformation reaches a maximum of 57.8 mm when the confining pressure is 2.0 MPa, the confining pressure range is 30 m, and the inverted arch thickness is 0.4 m. Bonding damage between the track slab and the backfill layer occurs at the boundary between the confining pressure zone and the non-confining pressure zone. The significant influence of insufficient inverted arch thickness on bond damage is not linear, the maximum bonding damage area increases from 45.5 m² at a thickness of 0.78 m to 75.8 m² at 0.5 m. The gaps between the backfill layer and the inverted arch are unevenly distributed laterally along the track, with the interlayer gaps curve transitioning from a “trapezoidal” shape on the outer rail side to an “M” shape on the inner rail side. The research results play an important role in the design and maintenance of ballastless tracks in tunnels under the action of TFH.