SHP solution of effect of elevated temperature on tunnel lining

摘要

Smooth hydrodynamic particle solution seems to be a suitable method for solving problems of influence of high temperatures on the FR concrete tunnel lining and surrounding rock. This meshless method suffers from one unpleasant property: it is not easy to describe the inhomogeneous geometrical boundary conditions. In our case, the highly elevated temperature is increasing and decreasing in a time scale on the boundary. After reformulating the problem into a form obeying boundary conditions being suitable for application of the SPH method, the 2D problem can be solved. This restriction to 2D is an impact of assumption that the fire is triggered along the length of the axial direction of tunnel. This follows from the observation at concrete locations where conflagrations inside of the tunnels took part. The most extreme temperature is prevailingly considered at 1200°C to fulfill European standards. As the mechanical and physical properties change nonlinearly a set of experiments in furnaces have been conducted to improve the characteristics of the material of tunnel lining and rock. Coupled modeling is applied to conduct convergence analysis providing results from experiments and numeric method to be in compliance. Simultaneous nonlinear equations are first formulated, involving stress analysis, influence of pore pressure, change of temperature, moisture, and degree of saturation. Nonlinear mechanical properties are based on the change of mechanical parameters, as are available from experimental studies. A couple of examples will follow the theory.