Cooling effect of ripped-stone embankments on Qing-Tibet railway under climatic warming

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 convec-tion for incompressible fluids porous media, the finite ele-ment formulae for heat convection in porous media are de-rived by using Galerkin抯 method. The temperature fields of the traditional ballast embankment and the ripped-stone mass embankment, constructed on July 15, have been ana-lyzed and compared under the case that the air temperature in Qinghai-Tibetan Plateau will be warmed up by 2.0℃ 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℃ or the yearly-average temperature at the native surface is larger than -1℃. The embankment will cause large thawing settlement. The rail-way embankment will be damaged by permafrost degrada-tion. 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.

高温冻土区U型块石路基长期降温效果及变形特征研究

U型块石路基作为块石护坡与块石基底两种结构路基的组合,同时也作为青藏铁路的一种主要补强措施,其在高温冻土区的长期降温效果备受关注。基于长期的现场监测资料,对青藏铁路楚玛尔河高温冻土区一处U型块石路基的长期降温过程、降温机制以及变形特征进行了研究。结果表明:U型块石路基表现出持续稳定的降温效果,路基下部多年冻土上限附近降温明显,上限抬升迅速,且进入稳定状态。基底块石层底、顶板温差存在明显冷暖季差异。阴坡侧块石层每年1月至3月初为相对强烈自然对流期,阳坡侧相对缩短半个月时间。受工程热扰动影响,深层的多年冻土在经历2~3年升温过程后,呈现显著的降温过程。路基变形整体表现为较小的沉降量,变形主要来源于早期路基下部高温冻土层的压缩变形。总之,U型块石路基在高温冻土区表现出长期有效的降温效果,变形量有限且已趋于稳定,路基整体稳定性可以得到保证。

昆明地区臭氧总量变化和气候关系的初步分析

利用 196 3～ 1992年期间昆明地区平流层臭氧、温度以及降水量等观测资料 ,分析及计算了该地区的臭氧演变趋势、冷暖和旱涝指数 .研究结果显示 :臭氧总量的变化包含着气候异常的信号 。

高海拔多年冻土区高速公路分离式通风管路基的降温效果研究

考虑到宽幅路基的“聚热效应”和复杂的多年冻土环境,拟建青藏高速公路建设所面临的关键问题是如何保证路基的长期热稳定性。基于现场监测数据和传热传质理论,建立分离式通风管路基三维数值模型,分析与预测未来50年通风管在青藏高速公路分离式路基中的工程效果。结果表明:分离式通风管路基具有较好的降温效果,能够保证路基及其下部多年冻土的长期热稳定性。但是,当隔离带宽度小于10m时,后幅路基管道内部风流变化特征受到隔离带宽度的显著影响,导致其对下部多年冻土的降温效果弱于前幅路基。此外,在隔离带较窄情况下,两幅路基之间隔离带区域存在局地增温效应,将对路基及其下部多年冻土产生严重的热扰动,不仅引起多年冻土上限下降、温度升高,而且增加了路基两侧下部土体温度场的不对称性。尝试将两幅路基通风管连通来弱化局地增温效应,但连通后路基及隔离带区域下部土体的热状况反而更差,说明这种方法未能有效解决局地增温效应的热影响。