Research Of Impermeability And Anti-cracking Properties Of Tunnel Secondary Lining Fiber Concrete

Cracking and leakage are the most serious damage of tunnel secondary lining concrete around the world. Cracking and leakage often lead to erosion damage and freeze-thaw damage, increase the humidity, decrease the work efficiency of fans and lamps, lower the reliability of tunnel lining structure.Based on the problems, by incorporating steel fiber (SF), carbon fiber (CF), the paper made a research of the workability, basic mechanical properties, constitutive relation, anti-impact properties and impermeability of tunnel secondary lining concrete.1. Finite element modeling analysis was conducted, the effect of surrounding rock stress and temperature on tunnel secondary lining was researched; the controlling measures of cracking and leakage were also summarized; and made the point that fiber concrete was one way to slove the problem of cracking and leakage.2. SF or CF could improve the cube compressive strength, flexural strength, axial compressive strength and splitting strength, and as the volume of fiber increased, values of all kinds of strength gradually increased; there was a synergistic effect between SF and CF; three dimensional linear relationship was established among strength index and types of fiber and the volume of fiber by the approach of matlab.3. As the volume of SF increased, the elasticity modulus increased correspondingly, and there was litter effect of the CF on the elasticity modulus; as the volume of SF or CF increased, the peak strain gradually increased, and bigger when SF and CF were hybrid, there was a linear relationship among the strain and and types of fiber and the volume of fiber; SF or CF alone could improve the compressive toughness significantly, when hybrid the toughness was bigger; the improvement of toughness mainly reflected in the toughness after the peak strength; the stress-strain curve was established based on Guo Zhen-hai model and CEB-FIP model.4. The anti-impact properties of fiber concrete were evaluated by the use of ACI model, test results shown that SF or CF could improve the impact toughness significantly; fiber bybritiation made the impact toughness much better; the improvement effect of impact toughness mainly reflected on the toughness after the cracking; by the introduction of hybrid effect index, there was a positive effect of the hybridity; the fracture mechanism of concrete was also analyzed by mechanics of fracture and so as to the mechanism of hybrid effect. There was a good coherence between compressive toughness and impact toughness.5. The impermeability of concrete was evaluated by the concrete water pressure test and concrete electric flux test, conclusion could be made that:SF or CF could improve the impermeability; the anti-permeability performance was better by the hybridity of SF and CF.