Knowledge Resource Center for Ecological Environment in Arid Area
| 青藏高原风沙堆积对冻土环境影响的实验研究 | |
| 其他题名 | Experimental study on influences of aeolian sand accumulation on frozen soil environment in the Qinghai-Tibet Plateau |
| 贺志霖 | |
| 出版年 | 2015 |
| 学位类型 | 硕士 |
| 导师 | 俎瑞平 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 青藏高原是中低纬度高原冻土的主要分布区，也是全球气候变化的敏感区。冻土是地-气系统相互作用和平衡的产物，对外界环境较为敏感，除受纬度、海拔和地质构造影响外，还受积雪、积沙、水体、植被等局地因素的影响。由于青藏高原独特的自然地理环境以及气候变化和人类活动的影响，高原沙漠化问题加剧。作为影响冻土环境的一种局地因素，沙漠化引起的地表风沙堆积通过改变地表辐射和能量平衡以及地表传热特性对冻土环境造成影响。目前，风沙堆积对冻土环境的影响过程及机理仍不明确。而且随着青藏铁路的全线开通，沿线部分路段风沙灾害严重，风沙堆积不仅压埋铁道设施，还会填埋碎石路基和通风管道，对路基的降温效果造成影响。本研究通过野外定位监测和室内模型实验，探讨风沙堆积对冻土环境的影响以及碎石路基积沙对其“主动冷却”降温效果的影响。研究结果如下： (1) 由于两个观测场地位置邻近，所以两个场地的地表辐射各分量总体上具有一致的变化规律，但在具体数值上具有一些差异。从一年的情况来看，积沙地表的净辐射值大于天然地表。积沙地表和天然地表土壤热通量的年总量值分别为103.87 MJ?m-2和104.10 MJ?m-2，这表明二者都是向地下传递热量，天然地表向地下传递的热量稍多于积沙地表。 2)青藏高原红梁河实验场6个积沙对比场（0、20、50、100、150、200cm积沙）一年的钻孔地温监测数据表明，积沙地表与天然地表（荒漠草地）下伏的季节冻土地温变化存在明显差异，中上层地温在冬半年（11～3月）和夏半年（5～9月）以及过渡月份（10月和4月）表现出不同的变化规律，而下层地温变化小且无明显变化规律：(a) 10月，各场地冻土均已融化，积沙地表表层（1 m以上深度）地温高于天然地表。(b) 冬半年，各场地地温降低，季节冻土从上向下单向冻结，各实验场冻结深度最深均达4.5 m；在冻结深度内，积沙地表地温高于天然地表，且沙层越厚温度越高；在这5个月内，与天然地表相比，积沙地表近地面（0.05 m深度处）地温比天然地表最大高7.68、10.67、9.28、5.53和0.80℃。 (c) 4月，积沙地表的中上层地温低于天然地表，天然地表的表层冻土开始融化。(d) 夏半年，各场地地温升高，积沙地表的中上层地温低于天然地表，且沙层越厚温度越低；在这5个月内，与天然地表相比，积沙地表的近地面（0.05 m深度处）地温比天然地表最大低9.38、11.37、13.01、8.42和3.78℃；期间，积沙地表下冻结深度达6 m，天然地表下冻结深度只有5 m；到9月，天然地表下冻土已完全融化，而积沙地表在2 m～6 m深度间仍有冻土分布。 (3)积沙对冻土温度影响模型实验得出相似结果：当试验箱气温为负温时期，积沙冻土的中上层温度比无积沙冻土高，且沙层越厚温度越高；当试验箱气温为正温时期，积沙冻土的中上层温度比无积沙冻土低，且沙层越厚温度越低，而正温时期正是冻土融化时期，积沙的降温作用可以延迟冻土融化。 (4) 碎石路基积沙模型实验表明，碎石层无积沙的冻土周期均温明显低于积沙填埋碎石层的冻土均温，碎石层上积沙越厚，冻土温度越高，这表明没有积沙的碎石层具有较好的降温效果，而积沙填埋碎石层会导致碎石路基“主动冷却”降温效果减弱。 |
| 英文摘要 | Qinghai-Tibet Plateau is the main distribution area of low latitude frozen soil. Frozen soil is the product of land- atmosphere system interaction and balance, which is sensitive to exterior environment. Not only latitude, altitude, geologic structure, but also snow accumulation, sand accumulation, water and vegetation have influences on frozen soil. Because the unique geographical environment, climate change and human activities, sandy desertification is more serious in Qinghai-Tibet Plateau. As a local influencing factor, aeolian sand accumulation alters land surface radiation and energy balance and surface heat transfer, influencing frozen soil environment. Now, the process and mechanism of influences on frozen soil is still not clear. In addition, as the Qinghai-Tibet Railway was opened, the sandy desertification problem emerges and intensifies. Aeolian sand accumulation not only buries railway facilities, but also buries crushed-rock embankment and ventilating pipe, influencing the proactive cooling effect of embankment. In this study, we explore the influences of aeolian sand accumulation on frozen soil environment and the cooling effect of crushed-rock embankment which buried by sand accumulation through field monitoring experiment and laboratory model experiment. The results showed that: (1) Because the two observation sites of radiation are proximity, all surface radiation components have a consistent variation, but have some difference in the specific value. From one year observation data, the net radiation of sand accumulation surface was more than that of natural surface. Annual total soil heat flux values of sand accumulation surface and natural surface were respectively 103.87 and 104.10 MJ?m-2, which indicated that the two underlying surfaces transfer heat to the ground, and the natural surface transferred a little more heat to the ground. (2) Based on one year data of six field monitoring sites of different sand thickness (0, 20, 50, 100, 150, 200 cm), we found that the temperature variation of frozen soil underlying sand accumulation surface and natural surface (alpine desert grassland) was obvious different. The middle-upper layer temperature of frozen soil showed different variation in the winter half year (November to March), summer half year (May to September) and the transition month (October and April), while the difference of the bottom temperature of frozen soil was small and no significant variation. (a) In October, the frozen soil of six field monitoring sites has been melted, and the upper layer (above 1 m depth) ground temperature of sand accumulation surface was higher than that of natural surface. (b) In the winter half year, frozen soil of six field monitoring sites began freezing from top to bottom, and the deepest depth reached 4.5 m. In the freezing depth, the temperature of frozen soil underlying sand accumulation surface was higher than that of natural surface, and the thicker the sand layer was, the higher the temperature was. Comparing with the natural surface, the near-surface (0.05 m depth) maximum increasing temperature of sand accumulation surface was respectively 7.68、10.67、9.28、5.53 and 0.80℃ in the five months. (c) In April, the middle-upper layer temperature of frozen soil underlying sand accumulation surface was lower than that of natural surface. What was more, the frozen soil underlying natural surface began to melt. (d) In the summer half year, the temperature of frozen soil of six field monitoring sites gradually increased. The middle-upper layer temperature of frozen soil underlying sand accumulation surface was lower than that of natural surface, and the thicker the sand layer was, the lower the temperature was. Comparing with the natural surface, the near-surface (0.05 m depth) maximum decreasing temperature of sand accumulation surface was respectively 9.38, 11.37, 13.01, 8.42 and 3.78℃ in the five months. During the period, the freezing depth of sand accumulation surface reached 6 m, and the freezing depth of natural surface reached only 5 m. In September, the frozen soil underlying natural surface has been completely melted, but there was still frozen soil distribution from 2 to 6 m depth under sand accumulation surface. (3) Laboratory model experiment of the influence of aeolian sand accumulation on frozen soil temperature showed the similar results. When the air temperature was negative (winter half year), the frozen soil temperature at middle-upper layer covered by sand layer was higher than that of no sand cover. The thicker the sand layer was, the higher the frozen soil temperature was. When the air temperature was positive (summer half year), the frozen soil temperature at middle-upper layer covered with sand layer was lower than that of no sand cover. The thicker the sand layer was, the lower the temperature was. It was the melting period during the summer half year, and the cooling effect of sand layer can delay the melting of frozen soil. (4) Model experiment of crushed-rock embankment buried by sand layer showed that the periods mean temperature of frozen soil covered with crushed-rock layer with no sand layer was lower than that crushed-rock layer buried by aeolian sand. The thicker the sand layer was, the higher the temperature was. It showed that crushed-rock layer had an effective cooling effect, but the cooling effect decreased when crushed-rock buried by aeolian sand accumulation. Aeolian sand accumulation weakens the proactive cooling effect of the crushed-rock embankment. |
| 中文关键词 | 风沙堆积 ; 冻土 ; 碎石路基 ; 地温 ; 青藏高原 |
| 英文关键词 | Aeolian sand accumulation Frozen soil Crushed-rock embankment Ground temperature Qinghai-Tibet Plateau |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287532 |
| 推荐引用方式 GB/T 7714 | 贺志霖. 青藏高原风沙堆积对冻土环境影响的实验研究[D]. 中国科学院大学,2015. |
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