Laboratory Thermo-Mechanical Coupling Test of Tunnel Lining Concrete

In order to study the relationship among the fire exposure time, the content of coarse aggregate, and the macroscopic damage of tunnel lining concrete, a thermo-mechanical coupling test device of lining concrete was independently improved according to the actual fire exposure characteristics of tunnel lining, and the damage law of concrete test blocks with 20%, 30%, and 40% coarse aggregate was studied under the load ratio constant of 28% and different fire exposure time. The results show that when there is no fire accident, no deterioration appears on the surface of the lining concrete under a small load, and the quality does not change greatly. The residual compressive strength increases. Under the action of thermo-mechanical coupling, as the fire continues, a few micro-cracks form on the surface of the test block after 0.5 h of fire exposure, and wide cracks appear on the surface after 1.0 h of fire exposure, with many small cracks distributed and some cracks crossing each other. After 2.0 h of fire exposure, the bottom surface of the test block is seriously damaged. The time and degree of fire development are crucial to the damage to the lining structure. As the content of coarse aggregate of concrete decreases, the internal temperature conduction velocity of concrete slows down; the temperature value at the same position becomes smaller, and the apparent damage increases significantly. The mass loss rate of concrete with 20% coarse aggregate can reach 8.14%, while that of concrete with 40% coarse aggregate is only 4.10%, which indicates that when the strength is the same, concrete with high-content coarse aggregate has better fire resistance. © 2023 Science Press. All rights reserved.