MODELING SOIL RESPONSE TO INTENSE HEATING FROM TUNNEL FIRES

This study investigates the response of saturated soils to intense heating from tunnel fires by numerical simulation. A general purpose commercial CFD code, FLUENT and a special porous media code, TOUGH2, are used. The conservation equations for porous media in each program are discussed and the numerical models are established. Two-dimensional simulations for the saturated coarse sand and the saturated fine sand are conducted and the results are compared with experimental data. It was found that models for capillary effects and relative permeability are required to describe the experimentally observed behavior. Without considering them, FLUENT predicts an inconsistent dry-out vapor zone in the soil column. TOUGH2 which includes these models gives the same two-zone structure observed in experiments, namely a liquid zone on the top and a two-phase zone at the bottom. The TOUGH2 results provide insight into the experimentally observed transient phenomena and agree well with experimentally observed trends