<p>To investigate the deformation and damage mechanisms of tunnel floor heave in horizontally stratified rock masses under complex geostress conditions, a large-scale physical model test was conducted. The experiment innovatively combined 3D printing technology with the cast-in-place process to produce a high-precision tunnel model capable of being loaded to failure. Meanwhile, a stratified rock mass fabrication method, involving layer-by-layer pouring with gypsum-based materials, was innovatively proposed and implemented. The model test results reveal a significant influence of horizontal geostress on the floor heave of railway tunnels in horizontally stratified strata. Notably, when the lateral pressure coefficient exceeds a certain threshold, the internal forces within the tunnel structure undergo significant changes, leading to a substantial increase in the floor heave. Tunnels experiencing floor heave issues are predominantly situated at low burial depths with high tectonic stress, and the root cause is attributed to the heave damage of stratified-interbedded rock below the tunnel bottom. This research reveals the deformation and failure mechanisms of tunnel floor heave, and proposes deformation control measures to reinforce the inverted arch structure and the surrounding rock at the tunnel bottom.</p>