Structure Strengthening Method for Enhancing Seismic Behavior of Soft Tunnel Portal Section

Tunnel portal sections always suffer serious damage under strong earthquakes. This paper aims to study the seismic performance of lining strengthening method in soft rock section by employing model test. Firstly, shaking table test considering cases, modified input motions, boundary condition, and monitoring equipment are conducted simulate response tunnel section. Then, increasing concrete grade is applied structure aseismic section, effects linings with different grades compared analyzed. The result shows that proportion total surrounding key factor affecting section; larger rock, more vulnerable earthquake damage; hard remarkable while limited stiffness strength than those rock; could hardly be improved only method. It suggested adopt both isolation design