The determination of the support pressure is critical to the excavation face stability of deeply buried shield tunnels in soft-over-hard ground conditions. Based on the limit equilibrium method, a calculation model for the limit support pressure was established, in which the variation in slip surface inclinations was considered, and a friction arch zone, a load-bearing arch zone, and a multi-layer wedge slip zone were composed. The effectiveness of the model in predicting the limit support pressure was verified through a case study and numerical simulations. The results indicate that soil displacement increases as the support pressure decreases, with more significant deformation observed in the upper soft soil. Moreover, a non-linear decrease in the limit support stress ratio is observed with increasing buried depth ratio. A linear decrease in the limit support stress ratio is observed with increasing cohesion and internal friction angle of the upper soft soil, whereas a near-linear increase is found with increasing proportion of the soft soil layer. This research provides a valuable reference for predicting the limit support pressure for tunnel excavation faces in similar geological conditions.