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Stability analysis of a fire‐loaded shallow tunnel by means of a thermo‐hydro‐chemo‐mechanical model and discontinuity layout optimization
Author(s) -
Sun Zizheng,
Zhang Yiming,
Yuan Yong,
Mang Herbert A.
Publication year - 2019
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/nag.2991
Subject(s) - spall , discontinuity (linguistics) , structural engineering , geotechnical engineering , thermal , materials science , computer simulation , stress (linguistics) , mechanics , engineering , simulation , mathematical analysis , mathematics , linguistics , philosophy , physics , meteorology
Summary When subjected to fire loading, shallow tunnels may experience loss of stability. This may result in large deformations and ultimately in local collapse of such structures. High temperature has a great negative influence on tunnels, not only because of thermal‐induced mechanical degradation of the heated lining but also because of thermal spalling in consequence of the build‐up of pore pressure. Thermal spalling causes quick loss of lining sections. Mechanical degradation sole can be simulated by thermo‐mechanical models, while consideration of mechanical degradation and spalling requires thermo‐hydro‐chemo‐mechanical (THCM) models and a spalling criterion. After simulation of both processes, the stability of a tunnel structure can be assessed by means of limit analysis. In this work, at first, a fully coupled THCM model is developed. Then, by using a “stress vs strength” criterion and a boundary shifting strategy, the coupled mechanical degradation and thermal spalling processes are captured, providing time‐dependent and space‐dependent information of the heated lining. Finally, a novel numerical approach, termed discontinuity layout optimization (DLO), is applied to quantify the stability of the tunnel structure with the help of a factor of safety. The proposed numerical procedure is used to conduct numerical studies with, as well as without, consideration of spalling. The results show that spalling has a great impact on the stability of the tunnel. It reduces the thickness of the lining section and accelerates the heating process of the inner concrete.