Abstract
Temperature differences between the surrounding ground and the tunnel lining will cause a variation of the tunnel lining forces. The hyperstatic reaction method (HRM) could be efficiently and simply used to investigate the impact of thermal load on tunnel linings. First, the steady state numerical solution is derived for a shallow circular tunnel to estimate the internal forces and displacements of tunnel lining caused by thermal load. The effective strain coefficient βTl is deduced to calculate the thermal stresses in tunnel lining. Secondly, the influence of the temperature difference on the internal forces of tunnel lining is investigated using the HRM method considering different lining elastic modulus, lining thickness and ground coefficient of thermal expansion. Lastly, the impact of fires which will be able to modify the elastic modulus of tunnel lining is investigated, which makes it possible to predict the damage of tunnel lining caused by fires.
Highlights
Tunnels have been extensively used for transportation, such as rail traffic, road and water; less attention is focused on the thermal stresses of tunnel lining caused by temperature differences
As temperature change is taken into consideration, the external loads consist of two parts in the analysis: (1) the additional thermal loads caused by temperature change; (2) the earth active loads applied by the ground
It is given that the ground-structure contact is rigid and the ground is perfectly restrained by the tunnel lining, so that the potential soil strains caused by temperature change could be totally converted to additional thermal stresses. σTs could be expressed as follows: σTs = ES·εths in which εths is the radial restrained thermal strain of ground caused by temperature change, which is given as follows: εths = αTS·∆T
Summary
Tunnels have been extensively used for transportation, such as rail traffic, road and water; less attention is focused on the thermal stresses of tunnel lining caused by temperature differences. Temperature change has an impact on the internal forces of tunnel lining; a few research works could be found that investigated the stresses and displacements of tunnels caused by a thermal loading. This paper starts with an introduction to the HRM method, including the groundstructure interaction and the loads applied to the tunnel lining An improvement of this method is presented to show how to estimate the thermal stresses caused by temperature change. A parametric analysis is presented to study the effect of temperature change on the internal forces of circular tunnel lining using the present method The following factors, such as the lining thickness, elastic modulus, and ground coefficient of thermal expansion, are considered. The proposed simplified method could be able to give a design reference for the tunnel facing the thermal impact
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