Seismic performance of steel strip reinforcement measure on double-arch tunnel with thin and straight mid-partition wall

The Ningqiao Tunnel project was taken as the research object, and a three-dimensional dynamic time-history numerical calculation model was established in FLAC3D based on seismic vulnerability analysis method. The full-process automation calculation of the incremental dynamic analysis method in seismic vulnerability analysis was achieved through secondary development by Python. The vulnerability curves of the double-arch tunnel structure with thin and straight mid partition wall under the eight different combinations of factors were given, including the measures with and without steel strip reinforcement, two directions of seismic wave incidences (horizontal and vertical directions), and two types of surrounding rock grades (IV and V grades). According to the vulnerability curves, the damage probabilities of the structure at the tunnel site under seismic fortification intensity were obtained. The seismic performance and the pattern of steel strip reinforcement measures were evaluated by comparing the damage probabilities. The actual effect of steel strip reinforcement measures was verified by comparing the failure patterns and damage degrees of similar model structures with and without seismic measures based on a large-scale shaking table test. Research results show that regardless of the factor combination, the steel strip reinforcement measures can effectively reduce the damage probabilities of the structure in different damage states. The effectiveness is significantly influenced by the surrounding rock grade but less by the direction of seismic wave incidence. Under the V grade surrounding rock condition, the probabilities of slight, moderate, and severe damages reduce by 51.94%, 41.29%, and 29.63%, respectively when the seismic waves arc incident in the horizontal direction, and reduce by 55. 68%, 48. 32%, and 35. 29%, respectively when the seismic waves are incident in the vertical direction. Under the IV grade surrounding rock condition, the probabilities of slight, moderate, and severe damages reduce by 16.45%, 11.19%, and 7.11%, respectively when the seismic waves arc incident in the horizontal direction, and reduce by 12. 23%, 9. 45%, and 7. 49%, respectively when the seismic waves arc incident in the vertical direction. In the shaking table test, the damage degree of the similar model structure with steel strip reinforcement measures under the most unfavorable factor combination is significantly lower than the structure without seismic measure. The steel strip reinforcement measures can effectively reduce the number of diseases, lower the degree of structural damage, and enhance the seismic performance of the structure by improving the overall load-bearing capacity of the structure. 6 tabs, 17 figs, 42 refs. © 2024 Chang'an University. All rights reserved.