Selection of Wall Rock Thickness for Thermal Stress Analysis of Circular Tunnel Concrete Lining

Abstract

When the thermal stress in the concrete lining of a spillway tunnel is computed using the finite-element method, the wall rock in the numerical model is generally taken to be a finite size. The selection of the thickness of the wall rock has a significant impact on the computational results for the thermal deformation and thermal stress in the concrete lining. The current study investigated the effect of the wall rock thickness on the thermal deformation and thermal stress in the concrete lining. A formula was derived for calculating the thermal displacement in an infinitely long, thick-walled cylinder, with the displacement being used as the outer boundary condition and the stress as the inner boundary condition. A formula was also derived for calculating the thermal displacement at the interface between the concrete lining and the wall rock of the circular tunnel. To reduce the influence of the wall rock thickness on the calculation accuracy, a method was developed for selecting the outer radius