Cooling effect of ripped-stone embankments on Qing-Tibet railway under climatic warming
Tóm tắt
The heat convection in ballast mass and ripped-stone mass in railway embankments is the problem of heat convection in porous media. In order to calculate the temperature distribution of Qing-Tibet railway embankment, from the governing equations used to study forced convection for incompressible fluids porous media, the finite element formulae for heat convection in porous media are derived by using Galerkin’s method. The temperature fields of the traditional ballast embankment and the ripped-stone mass embankment, constructed on July 15, have been analyzed and compared under the case that the air temperature in Qinghai-Tibetan Plateau will be warmed up by 2.0 °C in the future 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 larger than -3.5 °C or the yearly-average temperature at the native surface is larger than -1°C. The embankment will cause large thawing settlement. The railway embankment will be damaged by permafrost degradation. The ripped-stone mass embankment can not only resist the effect of climatic warm up on it but also provide cool energy for the permafrost under it. It can assure permafrost stability and not subjected to thawing. Therefore, it is highly recommended that the ripped-stone mass embankment be taken as the Qing-Tibet railway embankment structure in high-temperature permafrost regions so that permafrost embankment can be protected as possible as we could.
Tài liệu tham khảo
Trevisan, O. V., Bejan, A., Natural convection with combined heat and mass transfer buoyancy effects in a porous medium, Int. J. Heat Mass Transfer, 1985, 28(8): 1597–1611.
Poulikakos, D., Bejan, A., Natural convection in vertically and horizontally layered porous media heated from the side, Int. J. Heat Mass Transfer, 1983, 26(12): 1805–1814.
Royer, J. J., Flores, L., Two-dimensional natural convection in an anisotropic and heterogeneous porous medium with internal heat generation, Int. J. Heat Mass Transfer, 1994, 37(9): 1387–1399.
Amiri, A., Vafai, K., Analysis of dispersion effects and nonthermal equilibrium, non-Darcian, variable porosity incompressible flow through porous media, Int. J. Heat Mass Transfer, 1994, 37(6): 939–954.
Lee, K. B., Howell, J. R., Theoretical and experimental heat and mass transfer in highly porous media, Int. J. Heat Mass Transfer, 1991, 34(8): 2123–2132.
Sahraoui, M., Kaviany, M., Slip and no-slip temperature boundary conditions at the interface of porous, plain media convection, Int. J. Heat Mass Transfer, 1994, 37(6): 1029–1044.
Lai, F. C., Kulacki, F. A., Coulped heat and mass transfer by natural convection from vertical surfaces in porous media, Int. J. Heat Mass Transfer, 1991, 34(4): 1189–1194.
Nield, D. A., Estimation of the stagnant thermal conductivity of saturated porous media, Int. J. Heat Mass Transfer, 1991, 34(6): 1575–1576.
Hsu, C. T., Cheng, P., Wong, K. W., Modified Zehner-Schlunder models for stagnant thermal conductivity of porous media, Int. J. Heat Mass Transfer, 1994, 37(17): 2751–2759.
Bauer, T. H., A general analytical approach toward the thermal conductivity of porous media, Int. J. Heat Mass Transfer, 1993, 36(17): 4181–4191.
Qin, D. H., The Comprehensive Evaluating Report on the Environment Evolvement in West China, Beijing: Science Press, 2002, 57–58.