<p>With the continuous advancement of rail transit construction in China, the shield tunneling method has become the mainstream technique for tunnel engineering. When a shield machine traverses karst strata, karst features such as karst caves and dissolution zones result in an uneven excavation face. The contact state between the disc cutters and the rock mass during cutting undergoes dynamic changes, leading to abnormal wear or even failure of the cutters. This results in poor rock fragmentation efficiency and reduced shield driving performance. Based on explicit dynamic analysis and the Drucker-Prager plasticity criterion, this study employs Abaqus to investigate the mechanical responses of disc cutters and the cutterhead during cutting karst cave boundaries. In contrast to previous investigations that primarily address surrounding rock stability, lining mechanical behavior in karst formations, or cutter performance in homogeneous ground, this study focuses on the mechanical behavior of disc cutters and the cutterhead under uneven excavation surfaces caused by karst caves. It investigates the variation patterns of the peak and mean vertical forces during the process of cutting at the karst cave boundary under different cutting parameters. The deformation of the cutterhead corresponding to different numbers of suspended disc cutters under the condition of containing caves was studied. Numerical simulations were performed for scenarios with and without karst caves. Asymmetric loading and overturning moments are significantly more pronounced under karst cave conditions than in intact rock. The influence of cutterhead rotational speed and advance rate on the specific energy and overturning moment is explored.</p>