Abstract: In order to study the damage degree and performance characteristics of the tunnel lining structure after the fire, the compressive strength test and ultrasonic inspection of the tunnel lining concrete after the fire were carried out, and the residual resistance and the law of pressure intensity and speed of ultrasonic sound of the tunnel lining concrete under different fire time (2,3,4 h) was analyzed. The results show that: in the range of 200~800 ℃, under different fire time, the fire temperature and residual compressive strength, ultrasonic sound velocity and residual compressive strength have a good linear relationship, and with the increase of fire time, the ultrasonic sound velocity and compressive strength gradually decrease; Scanning electron microscopy-SEM shows that there is a good correlation between fire temperature, residual compressive strength and ultrasonic sound velocity. In addition, three calculation models of tunnel lining concrete compressive strength, fire temperature, and ultrasonic sound velocity in the range of 200~800 ℃ under different fire time have been established.

Key words: tunnel fire; lining concrete; compressive strength; ultrasonic testing; damage assessment