Laboratory and Numerical Simulation of the Evolution of a River's Talik
Résumé
Experiments simulating the evolution of a river talik were performed in a cold room where a small channel carried flowing water through frozen saturated porous soil in a hydraulic flume. The sensitivity of thaw propagation to water temperature and velocity was determined to indicate the relative importance of these controlling parameters. Two types of soils were investigated (sand and silty clay), corresponding to contrasting hydrological, thermal and mechanical behaviours. The experimental results show that the sensitivity to water temperature was much higher than that to water velocity for the ranges considered. The experiments were compared with results from one-dimensional numerical simulations to identify the thermal boundary conditions of the riverbed and to evaluate the capacity of the numerical code to represent the propagation of heat at depth. The results showed that the proper boundary conditions are of the Neumann type, where flux is expressed as a coefficient multiplied by the temperature difference between water and the soil surface. The value of this coefficient is evaluated as a function of flow velocity based on these experiments. As a first-order approximation, this coefficient is assumed to be constant when considering seasonal flow variations.
