Effect of climatic warming on the temperature fields of embankments in cold regions and a countermeasure

摘要

The heat convection in ballast mass and broken rock mass in railway embankments is the problem of heat convection in porous media. In order to calculate the temperature distribution of the Qing-Tibet railway embankment, from the governing equations used to study forced convection for incompressible fluids porous media, the finite-element formulas for heat convection in porous media are derived by using Galerkin's method. The temperature fields of the traditional ballast embankment and the broken rock mass embankment, constructed on July 15, have been analyzed and compared under the case that the air temperature on the Qing-Tibet plateau will warm up by 2.0degreesC in the next 50 years. The calculated results indicate that the permafrost 5 m below the traditional ballast embankment will be thawed in the regions in which the air yearly average temperature is higher than -3.5degreesC or the yearly average temperature at the native surface is higher than -1degreesC. The embankment will undergo large thawing settlement and even liquidize. The railway embankment will be damaged by permafrost degradation. The broken rock mass embankment not only can resist the effect of climatic warming up on it but also can provide cool energy for the permafrost under it. It can assure permafrost stability and not be subject to thawing. Therefore, it is highly recommended that the broken rock mass embankment be used for Qing-Tibet railway embankment structure in high-temperature permafrost regions so that permafrost embankment can be protected as well as possible.