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Study on the Tunnel Lining Cracking Patterns and Failure Ranges under Fire Scenarios
(1 School of Highway, Chang′an University, Xi′an 710064; 2 Engineering Research Center for Large Highway Structure Safety of Ministry of Education, Chang'an University, Xi′an 710064)
Abstract Tunnel fires pose a threat to human life and have an impact on the structural safety of tunnels. First, this paper establishes a 3D temperature field of the fire smoke according to the actual fire conditions in a metro running tunnel. Then, the basic equations and solutions to the lining temperature field during the fire are derived by taking into consideration the thermal convection, heat conduction between the tunnel wall and heating smoke, the nonlinearity of heat transfer properties of the lining materials as well as the concrete spalling, The accuracy of the proposed method is verified by comparing with the test results. Furthermore, combined with the 3D temperature field obtained from the solution, the stress in the lining during the fire is solved by the finite element method under considering the lining material's thermodynamic properties as the non-linear functions to the temperature. Finally, the lining failure patterns and ranges are analyzed according to the elastic failure criterion and the triaxial stress conditions. The study results show that the lining failure is mainly caused by the compressive crushing of the inner concrete; after 2h of the fire, the compressive stress of the lining exceeds the compressive strength within the range of 16 m along the driving direction, 12 cm thickness of concrete and 112° from the vault to the sidewall; at the depth of main reinforcements of the lining segment, the concrete stress is less than the strength within 30 min; the failure pattern of the segment is mainly flake splitting; and the bolts have insufficient shear strength in the late stage of the fire, within the range of 37° at both sides of the vault.
Abstract：
Tunnel fires pose a threat to human life and have an impact on the structural safety of tunnels. First, this paper establishes a 3D temperature field of the fire smoke according to the actual fire conditions in a metro running tunnel. Then, the basic equations and solutions to the lining temperature field during the fire are derived by taking into consideration the thermal convection, heat conduction between the tunnel wall and heating smoke, the nonlinearity of heat transfer properties of the lining materials as well as the concrete spalling, The accuracy of the proposed method is verified by comparing with the test results. Furthermore, combined with the 3D temperature field obtained from the solution, the stress in the lining during the fire is solved by the finite element method under considering the lining material's thermodynamic properties as the non-linear functions to the temperature. Finally, the lining failure patterns and ranges are analyzed according to the elastic failure criterion and the triaxial stress conditions. The study results show that the lining failure is mainly caused by the compressive crushing of the inner concrete; after 2h of the fire, the compressive stress of the lining exceeds the compressive strength within the range of 16 m along the driving direction, 12 cm thickness of concrete and 112° from the vault to the sidewall; at the depth of main reinforcements of the lining segment, the concrete stress is less than the strength within 30 min; the failure pattern of the segment is mainly flake splitting; and the bolts have insufficient shear strength in the late stage of the fire, within the range of 37° at both sides of the vault.
HAN Xingbo1,
2 ZHAO Weifeng1
.Study on the Tunnel Lining Cracking Patterns and Failure Ranges under Fire Scenarios[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(3): 33-42
2021, Vol. 58 