Relationship between the diameter variation rate of prefabricated segmental tunnels and performance targets

The seismic performance design of prefabricated segmental tunnels plays a crucial role in contemporary underground structure design. To address the inadequacies in the current definition and description of seismic performance for prefabricated segmental tunnels, this study focuses on the division of structural performance levels for shield tunnel structures and determines the deformation limit values for their seismic and waterproof performance objectives. The performance objectives of the prefabricated segmental tunnels were divided into five levels: basic intact, operational, repairable, medium-repairable, and severely damaged. To obtain quantifiable performance indicators for prefabricated segmental tunnels that correspond to these performance objectives, this study investigated two adjacent ring segments of 19 sealed roof blocks at different positions based on four classic sites. Finite element models with refined details were utilized for the pushover analysis to obtain the capacity curves for the segment structures. Based on the relationship between the capacity curves and the performance objectives, the limit values of the diameter change rates for each case were determined using geometric plotting methods. The limit values of the diameter change rates for the prefabricated segmental tunnels corresponding to the five performance levels were determined to be 1/1850, 1/320, 1/180, 1/160, and 1/130. Finally, an index system was established for the seismic performance of prefabricated segmental tunnels. The proposed angle limits provide foundational guidance for the seismic design of prefabricated segmental tunnels.