Study of Formation Mechanism and Blocking in Giant Debris Flow at Hongchun Gully Yingxiu Town Wenchuan County

From Aug. 12th to 14th 2009, the catastrophic giant debris flow occurred in Hongchun gully Yingxiu town Wenchuan County, Du-Wen higyway in the period of heavy storm. It has cut off the Du-wen highway traffic totally and weir of Ming River became the damming body, which diverted the river plug body and rushed into Yingxiu doxens of new houses. The overflow river isolated Yingxiu towm serious and threat the post-disaster reconstruction triumph.It have important significance that to study the basic features，the deformation and failure mechanism ，the types and countermeasures to prevent and control the scale, the prevention and cure of high seismic intensity of debris flow in Hongchun gully. Base on the researches of geo-hazards background, conditions and basic features with the example of Hongchun gully debris flow, the author Analyzed the formation mechanism of debris flow and specific reason of blocking river and breaking highway, forecasted that causes of development of debris flow, also analyzed the stability of material sources in Hongchun gully’s debris flow. Then the author put forward that the formation of debris flow in Hongchun gully and blocking of Minjiang River are related closely to rich loose material sources induced by Wenchuan earthquake, the heavy rainfall, and its unique landform. Researches show that the giant debris flow in Hongchun gully started from Ganxipu lateral ditch in the upstream, the materials collected and dam-broke, It collected the material sources of the main ditch, crushed into Minjiang River, joined with the material sources of Shaofan gully debris flow in the river-upstream, blocked river and became dam lake. In a word,it is necessary to strengthen the control of the debris flow because that it is very rich material sources in Hongchun gully, and prevent hazard of the debris flow burst again.