西藏东南部泥石流堵塞坝的形成机理

Formation of Dam from Debris Flow in the Southeast Tibet

西藏东南部山高谷深,冰川发育,冰碛等松散堆积物厚度大,经常发生大型或特大型泥石流堵断主河,形成堵塞坝。针对西藏东南部4条典型泥石流沟所发生的7次大型或特大型泥石流中,有5次形成堵塞坝,来剖析泥石流堵塞坝形成的机理和主要因素。提出由于冰雪崩、冰湖溃决或大规模滑坡活动,所激发的首阵或前几阵大流量、高速度、多巨砾,并与主河正交的粘性泥石流,最容易形成堵塞坝。

Glaciers with their deposits abound in the high mountains of the Southeast Tibet. Large-scale debris flow occurs frequently from these deposits and forms dams that block mainstreams. In this paper, seven events of large-scale debris flows occurred in four gullies, from which five blocking dams resulted, are discussed in details, focusing on the major factors impacting the dam formation. Result shows that the first surge group caused by snow and ice avalanches, ice-lake break, and large-scaled landslides, with peak discharge and high speed, and in abundance with boulders, are most likely to form blocking dams.