川藏公路波密段九绒沟泥石流形成机制研究
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摘要
川藏公路波密段沿着帕隆藏布展布。帕隆藏布流域是我国海洋性冰川集中分布的地区,也是泥石流等地质灾害的强活动区。因流域内冰川分布范围不一,泥石流发生受气温的影响程度存在较大差异。帕隆藏布下游无冰川流域内的泥石流与气温无关,如帕隆藏布下游的加玛其美沟泥石流,但中游以上的泥石流却与气温有关。该文以帕隆藏布中上游九绒沟2014-2015年内的4次泥石流为例,详细分析了泥石流暴发前的降雨过程,并对降雨和气温在泥石流起动中的作用机制进行了分析。研究发现,3次泥石流仅由暴雨激发,其作用机制与常规暴雨泥石流类似,即由降雨径流侵蚀地表物质产流,为"低温+暴雨"模式;而2014年8月18日泥石流与迅速升高的气温关系密切,为"高温+降雨"模式,其作用机制在于气温升高导致土体内部冰颗粒快速消融从而放大土体活性,降雨径流侵蚀湿润的活动性土体而迅速产生泥石流。二者的差异在于高温迅速放大了冰碛物的活性,增加了表层土体的含水量,从而降低了泥石流产生所需要的降雨阈值。
The Sichuan-Tibet highway stretches along with the Parlung Zangbo river,where the temperate glacier and debris flows are highly concentrated. As the distribution of glacier is uneven is each catchment,debris flows is more or less affected by air temperature which enhance glacier retreat. In the downstream of Parlung Zangbo,the occurrence of debris flows in non-glacier catchment is found to be not correlated with air temperature fluctuation,such as which in Jiama valley; however,debris flows in the middle and upper Parlung Zangbo could be affected by air temperature. In this paper,4 debris flows occurred in 2014 ～ 2015 in Jiurong Valley of the upper Parlung Zangbo are applied to analyze the rainfall process before debris flows and the effect of rainfall and air temperature on debris flow occurrence. The research shows 3 debris flows were generated by rainfall and the mechanism is similar with the normal storm induced debris flows,which is"low air temperature + storm"type. Debris flows occurrence On Aug. 18 th,2014 is highly correlated with the mushrooming air temperature. The effect of "high air temperature + rainfall"lied in soil activity was greatly amplified because the mushrooming air temperature drove internal ice particle ablation and a surface layer with high water content,resulting into less rainfall threshold required to generate surface runoff and the following debris flows.
The Sichuan-Tibet highway stretches along with the Parlung Zangbo river,where the temperate glacier and debris flows are highly concentrated. As the distribution of glacier is uneven is each catchment,debris flows is more or less affected by air temperature which enhance glacier retreat. In the downstream of Parlung Zangbo,the occurrence of debris flows in non-glacier catchment is found to be not correlated with air temperature fluctuation,such as which in Jiama valley; however,debris flows in the middle and upper Parlung Zangbo could be affected by air temperature. In this paper,4 debris flows occurred in 2014 ～ 2015 in Jiurong Valley of the upper Parlung Zangbo are applied to analyze the rainfall process before debris flows and the effect of rainfall and air temperature on debris flow occurrence. The research shows 3 debris flows were generated by rainfall and the mechanism is similar with the normal storm induced debris flows,which is"low air temperature + storm"type. Debris flows occurrence On Aug. 18 th,2014 is highly correlated with the mushrooming air temperature. The effect of "high air temperature + rainfall"lied in soil activity was greatly amplified because the mushrooming air temperature drove internal ice particle ablation and a surface layer with high water content,resulting into less rainfall threshold required to generate surface runoff and the following debris flows.
引文
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[2]中国科学院水利部成都山地灾害与环境研究所,西藏自治区交通厅科学研究所.西藏泥石流与环境[M].成都:成都科技大学出版社,1999b.
[3]李德基,游勇.西藏波密米堆冰湖溃决浅议[J].山地学报,1992,10(4):219-224.
[4]朱平一,程尊兰,游勇.川藏公路培龙沟泥石流输砂堵江成因探讨[J].自然灾害学报,2000,9(1):80-83.
[5]刘建康,程尊兰.西藏古乡沟泥石流与气象条件的关系[J].科学技术与工程,2015,15(9):45-49.
[6] DENG M,CHEN N,LIU M. Meteorological factors driving glacial till variation and the associated periglacial debris flows in Tianmo Valley,south-eastern Tibetan Plateau[J]. Natural Hazards&Earth Systemences,2017,17(3):345-356.
[7] Iverson R M.,Reid M E,La Husen R. G. Debris flows mobilization from landslides[J]. Annual Review of Earth and Planetary Science,1997,25:85-138.
[8] Tognacca C,Bezzola G R and Minor H E. Threshold criterion for debris-flow initiation due to channel bed failure[C]//Proceedings Second International Conference on Debris Flow Hazards Mitigation,Prediction and Assessment,edited by:Wieczoreck,G. F.,Taipei,2000:89-97.
[9]高登义.雅鲁藏布江水汽通道考察研究[J].自然杂志,2008,30(5):301-303.
[10]刘洋.基于RS的西藏帕隆藏布流域典型泥石流灾害链分析[D].成都:成都理工大学,2013.
[11]罗德富,毛济周,朱平一,等.川藏公路南线(西藏境内)山地灾害及防治对策[J]. 1996.
[12]王洋.沟床物质起动形成泥石流的临界条件[D].北京:中国科学院大学,2016.
[13]庄建琦,崔鹏,葛永刚,等.降雨特征与泥石流总量的关系分析[J].北京林业大学学报,2009,31(4):77-83.
[14]郭晓军,李泳,崔鹏.降雨对泥石流源地土体活动的指数式放大效应[J].山地学报,2013,31(4):406-412.
[15]李巧媛,谢自楚.高原区气温垂直递减率的分布及其特点分析———以青藏高原及其周边地区为例[J].石河子大学学报(自科版),2006,24(6):719-723.
[16] Davies M C R,Hamza O and Harris C. The effect of rise in mean annual temperature on the stability of rock slopes containing icefilled discontinuities[J] Permafrost Periglac.,2001,12:137-144.
[17] Bommer C,Fitze P and Schneider H. Thaw-consolidation effects on the stability of Alpine talus slopes in permafrost[J] Permafrost Periglac.,2012,23:267-276.