Effect of temperature on deep lined circular tunnels in isotropic and transversely anisotropic elastic ground
Abstract
A tunnel is a passageway constructed through soil or rock. It is one of the most important underground structures and has been widely used in transportation. Much research has been done on tunnel performance and on the interaction between ground, excavation, liner installation and support. The work has provided a better understanding of the interplay that exists between deformations and stresses transferred from the ground to the support. Significant insight into the problem has been provided by closed-form analytical solutions. A number of analytical formulations have been obtained for underground openings and lined tunnels under different scenarios, namely shallow or deep tunnels in the dry ground under geostatic loading, for static and seismic loading, plastic, poro-elastic, and poro-plastic conditions. However, considerably less attention has been given to thermal stresses in a tunnel. Temperature changes due to e.g. fire can cause cracking and damage to the liner and surrounding ground. In fact, a number of tunnels have suffered serious damage due to thermal loading. The French Channel Tunnel fire in 1996 and the Italian Mont Blanc tunnel fire in 1999 are well-known examples. The goals of this study are: (1) develop a general formulation for a deep circular lined tunnel in isotropic ground for thermal loading; (2) derive analytical solutions for stresses and displacements caused by thermal load for a lined circular tunnel under a transversely anisotropic ground where the ground anisotropy axis coincides with the stacking direction; (3) evaluate stresses and displacements for a lined deep tunnel in a transversely anisotropic medium also under thermal loading, with the ground anisotropy axis perpendicular to the stacking direction. Comparisons between the analytical solution obtained and the results obtained from ABAQUS for a number of select cases provide confidence in the formulations obtained. A parametric study has been performed to investigate the effects of Young’s modulus, Poisson’s ratio, thermal conductivity and the coefficient of thermal expansion on the behavior of the liner and ground, for a tunnel in a transversely anisotropic ground with the axis of the tunnel along one of the axis of elastic symmetry. The results of the study show that the Young’s modulus and the coefficient of thermal expansion are the most important parameters that determine the stresses and displacements of the liner and ground. The analysis also shows that the thermal conductivity has a significant effect on the temperature distribution in the ground.
Degree
M.S.C.E.
Advisors
Bobet, Purdue University.
Subject Area
Geotechnology|Civil engineering
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