Study On The Basic Characteristic Sand Disaster Chain Of Typical Glacial Lake Out Burst Debris Flow In Tibetan Southeast Of Linzhi Prefecture

Tibetan southeast of Linzhi prefecture as one of the most serious regions ofdebris flow disaster in China. Especially in recent years, affected by global climatechange, glacier melting speed, debris flow disasters occurred frequently, whichbrought great harm to Linzhi prefecture. Linzhi prefecture is located in the southeastof Tibet,China. The area of glaciers and perennial snow cover6728.2squarekilometers, which occupy5.7%of the land area. The south of Linzhi prefecture lies toIndian Ocean, it belongs to the oceanic monsoon climate, so the climate generally haslittle differences, with abundant water vapor. In order to make a survey of debris flowdisaster chain, We did the experiment of debris flow gully bed propose starting testand Moraine Lake dam-break to obtain the debris flow gully propose startingcondition and failure condition. At the same time according to the characteristics ofthe previous research of glacial lake outburst debris flow disaster chain, summed upthe following conclusions:(1) According to the field survey of4debris flow gullys of Linzhi prefecture,wefound that the loose solid material are abundant in the channel and both coasts.Derived from the channel upstream of the new and old moraine and channel of thelandslides, The granules are in the poor roundness, which are mainly rubbles. Aftersampling screening the solid particle median diameter range of D50to4-9mm,non-uniform coefficient Cu in the range of20-62, for non-uniform gravel.(2) Laboratory physical simulation experiment of Glacial lake outburst debrisflow gully propose starting was carried out in9groups, respectively from the startingdischarge per unit width, water depth, averageflow velocity, the surface starting flumeslope, packing analysis layer thickness, to get the starting discharge per unit width, depth and flume slope was negatively related to the linear relationship, startingdischarge per unit width, depth and linear positive relationship between accumulationlayer thickness; average flow velocity and flume slope, accumulation related linearlayer thickness is directly proportional. In the verification of the experiment, theobtained experimental results according to the similarity ratio accord with the realsituation.(3) In the application of the results, with differential method, we reached aconclusion that the starting flow under the relatively slope and starting depthrelationship, calculated to obtain the starting flow and starting depth of Xiajuepu gully,Pailong gully, Tianmo gully Which were used to predict the critical value of this kindof debris flow conditions.(4) Laboratory physical simulation experiment of lake outburst was carried out in9groups, obtained the Negative correlation by analyzing the relationship betweenSurge flow, water depth and flume slope; and positive linear relationship by analyzingthe relationship between Breaking depth and height of dam body.(5) The debris flow disaster chain depends largely on the formation of landslide,the terminal moraine levee ice, ice lake the size of Moraine-Dammed lake outbursteffect, along the loose material supply status and channel characteristics. According tothe factors affecting outburst flood evolution, summarized three major disaster chaintypes namely the outburst flood and subaerial debris flow, outburst flood-viscousdebris flow, outburst flood-subaerial debris flow-landslide(collapse)-viscousdebris flow-blocking river-flood.