A Study On The Tunnel Lining Structure Damage Under High Temperature Impact Loading And Thermal Insulation Using Geoplymer

As the result of the rapid development of industrialization,more and more dangerous chemicals need to be transported to all parts of the country by highway in China.The highway tunnels as an indispensable part in this process need to be researched.Due to the unique type of highway tunnel,once the combustion and explosion occur in the tunnel,the tunnel lining structure will inevitably face the high temperature combustion and explosion impact damage.In this paper,to research the damage of arch tunnel lining structure caused by high temperature impact,the damage experiment and the simulation were used.The research contents and achievements shown as follow:1)Based on the Fluid-Solid Coupling,a full-scale combustion model of chemicals transport vehicle was established.The temperature time history curve at different positions is monitored.The burning experiment with RABT curve was carried out on a high-temperature open hearth furnace covered with full-scale tunnel lining segments.When the vehicle burns on the left of the tunnel,the plume effect of the flame will cause higher temperature areas at the arch waist and arch shoulder compare burns in the middle of the tunnel,the damaged area also transfered.2)Research on impact damage to lining structure.The impact damage of tunnel lining structure is studied under non-contact explosive conditions with the considering of the confining pressure and the equivalent TNT model.The impact elevation and quality of the test stand are calibrated according to the peak overpressure at different locations of the tunnel lining.After cut the burnt tunnel lining segments we carry out the impact tests according to the different locations.Damage images of lining structures at different locations were obtained by highresolution non-destructive CT scanning.3)Research on micro-fracture of lining structure under coupling action of high temperature and pressure.Different parameters of particle parallel-bond model at different temperatures were calibrated by the stress-strain curves.The boundary conditions of temperature and impact are introduced to calculate high temperature damage and impact damage of meso-scale concrete model under real aggregate distribution.Finally,the simulated damage images at different locations of tunnel lining structure were obtained.4)The fractal theory was used for the quantitative analysis of the simulated damage images and the experimental CT scanning images.The safety factors of the feet,arch shoulder and ceiling of the arch were calculated according to the tension and compression conditions at different locations of the tunnel.The high temperature of the vehicle combustion makes the safety factor of the arch ceiling decreased from 10.1 to 0.2 and the safety factor of the arch shoulder decreased from 8.3 to 3.2 under the same impact pressure.Based on this analysis,it is concluded that high temperature is the major factor to reduce the tunnel safety factor.5)Increase the thermal insulation capacity of tunnel lining structure.The interface between concrete and geopolymer was designed and improved.The energy release rate of interface cracks was increased from 0.3 J/m2 to 2.5 J/m2 after the grooving.The interface strength was increased by 10 times.Finally,the improved interface strength was explained and analyzed from the perspective of the stress intensity factors at the front of mixed mode fractures.The damage and interface strengthening of tunnel lining structure under high temperature and explosion conditions were studied in this dissertation.Through the numerical simulation of different scales and corresponding experimental exploration,a good outcome in theoretical analysis and engineering application has been achieved.