With the rapid advancement of rail transit, shield tunnels have been extensively constructed worldwide. However, leakage at the shield tail can lead to severe consequences, including shield machine subsidence, structural damage to the tunnel, or even catastrophic tunnel collapse. Research on tunnel collapse induced by shield tail leakage remains in its infancy. The mechanisms underlying such accidents are not yet fully understood by researchers and engineers, and effective preventive measures have yet to be developed. In this study, a reducedscale model test was conducted to investigate the processes and mechanisms of tunnel collapse induced by shield tail leakage. The findings reveal that tunnel collapse is primarily triggered by the impact loads generated from the destabilized soil cave. The soil cave, formed due to erosion caused by leakage, propagates upward in a cycle of destabilization and regeneration until the ground surface collapses, resulting in load redistribution around the tunnel. Additionally, the study compares tunnel collapses induced by shield tail leakage and connecting passage leakage, highlighting that while both share similar collapse mechanisms, their boundary conditions differ. The coupling effect between the tunnel structure and surrounding soil is more pronounced in shield tail leakage, leading to more intense load fluctuations and greater structural damage to the tunnel.