Seismic performance of double-layer tunnel linings: a multi-performance-level framework

This study presents a comprehensive investigation into the seismic behavior of a double-layer tunnel lining system, focusing on damage progression, failure mechanisms, and load transfer under varying seismic intensities. Using finite element modeling and theoretical formulations, the response of both primary and secondary linings was analyzed in terms of stiffness degradation, plastic hinge formation, crack propagation, dominant frequency shifts, and interface slip behavior. The findings reveal a progression of failure beginning with localized cracking and bending in the primary lining, followed by stiffness degradation and load redistribution to the secondary lining. Three performance levels including Primary Performance Level, Second Performance Level, and Critical Performance Limit, were identified. Interface slip conditions fully bonded, partially bonded, and fully debonded, were shown to significantly affect load transfer efficiency and structural integrity. Full-slip conditions reduce internal forces but increase displacement demands, while rigid connections concentrate stress but enhance structural capacity.