青藏铁路抛石护坡和保温材料复合路基温度场特征非线性分析

采用多孔介质中流体的连续性方程、动量方程及能量方程,针对青藏铁路的气温和地质条件,对抛石护坡路基(无保温材料)及其在靠近路基顶部增设保温材料后的温度场特征进行了分析和比较.结果表明:在年平均气温为-4.0℃的青藏高原多年冻土区,考虑未来50 a气温上升2.6℃条件下,抛石护坡路基对其下部多年冻土可起到一定的保护作用;但由于气温升高的影响,路基中心处出现终年融化夹层;计算中发现当抛石护坡达到一定厚度时,单纯依靠增加抛石护坡厚度并不能明显增加其对路基中心处的降温效果;而增设保温材料后的抛石护坡路基可有效减小路基中出现的融化夹层,确保冻土路基的稳定.因此,建议在高温多年冻土区使用抛石护坡路基结构时,应考虑使用保温材料作为一种对抛石护坡路基进行保温补强的措施.

Nonlinear Analysis of the Temperature Field of the Embankment with Crushed-Rock Revetment and Insulation along the Qinghai-Tibetan Railway

The embankment with crushed-rock revetment has been widely used in the construction of Qinghai-Tibetan railway.In order to sufficiently protect the underlying permafrost,based on the temperature and geology conditions of the Qinghai-Tibetan railway,a numerical representation of the unsteady two-dimensional continuity,momentum and energy equations of thermal convection for incompressible fluid in porous media is used to analyze and compare temperature characteristics of the embankments with crushed-rock revetment,with and without insulation.The calculated results indicate that in the area where the mean annual air temperature is-4.0℃ and under the assumption that the air temperature will rise by 2.6℃ in the future 50 years,the embankment with crushed-rock revetment and without insulation can protect the underlying permafrost to a certain extent.However,because of the influence of global warming,a residual thawed layer will occur in the middle of roadbed.Furthermore,when the revetment thickness reaches a certain value,the cooling effect of the crushed-rock revetment on the middle part of roadbed can not effectively increase by adding its thickness only.But the embankment with crushed-rock revetment and insulation can effectively reduce the residual thawed layer in roadbed and ensure the stability of permafrost roadbed.Therefore,it is proposed that in warmer permafrost regions,the insulation should be used to increase the cooling effect of embankment with crushed-rock revetment.