The prediction of a tunnel seismic instability threshold is a key challenge in seismic design and disaster reduction. Current methods have shortcomings in effectively integrating the synergistic effects of surrounding rock and tunnel linings. To this end, a new prediction framework based on the loading/unloading response ratio (LURR) theory is proposed. First, three core components of the LURR model are introduced to control the dynamic response of tunnels. Subsequently, the evolution of LURR under different seism…