Road Tunnel Fire Lining Concrete Specimens Injury Pilot Study

With the increase of length, traffic density of highway tunnels, the potential threat of fire has also increased. In addition to enormous social influence and economic losses, considerable damage to the tunnel lining are caused when a fire breaks out in a tunnel, resulting in the reduction of carrying capacity and usage security of tunnel lining structure as well as threat to the safety operation in the future or even the collapse of tunnel structure. Therefore, there is important theoretical value and practical significance to study the mechanical properties'injury law of tunnel lining concrete material subjected to high temperature.Through fire ablation experiment and theoretical analysis, the residual strength, injury and weak links of tunnel lining concrete test blocks subjected to high temperature, which have different water contents, are studied in this dissertation.The main fingings read as follows.(1) The changing conditions in apparent morphological and organizational structure of concrete test blocks under different temperature and water content situations are compared and analyzed;(2) In addition to the establishment of function relationship between residual strength and temperature, the law of temperature's influence on the residual strength of lining concrete test blocks is obtained.The results show that when the temperature exceeds 400℃, the compressive strength of concrete test blocks decreases significantly and the splitting tensile strength decreases faster than the compressive strength under high temperature;(3) The law of water content's influence on the residual strength of lining concrete test blocks is obtained. The results show that the deterioration of fire resistance of concrete at high temperature is exacerbated by the water in the concrete; the higher the water content is, the more seriously the concrete hurts;(4) Through tracking of experiment process and record, the initial burst time, critical temperature, and water content range of C25 concrete are obtained when burst occurs at high temperature.The experimental data and results analysis of this dissertation may provide reference for fire protection design and technical support for damage identification, reinforcement and repair of post-fire tunnel lining structure.