【摘要】 自2008年汶川地震以来,四川省绵竹市清平乡雍家沟已暴发过多场泥石流,造成了严重的堵断公路和堵塞河流事件,其中,2012年"8·18"暴发的泥石流规模最大,造成绵远河全部堵塞。通过分析2010年"8·13"与2012年"8·18"两场泥石流的降雨过程发现,雍家沟暴发泥石流的前期累积雨量在增加,激发雨强在降低。2008年汶川地震导致雍家沟的主沟和支沟内堆积了大量的松散固体物质。野外调查发现,雍家沟多次暴发泥石流的活动路径并不一致,其中,2012年"8·18"泥石流主要沿1号支沟活动,沟道的侵蚀宽度随着与主沟沟口距离的增加而变窄,沟道内剩余堆积体厚度随着距离的增加呈现先增后减的规律,且沟道内的物质粒径分布具有随机性。对雍家沟在不同暴雨频率下暴发泥石流可能引起的堵江情况进行了分析,结果表明,在暴雨频率大于20%的情况下暴发泥石流便可造成堵江事件,甚至可将主河全部堵塞。更多还原

【Abstract】 After the 2008 Wenchuan earthquake,debris flow events constantly occurred in the Yongjia gully,which caused serious incidents of road blocked and river damming.The largest scale event was on August 18,2012 which simultaneously caused the Mianyuan River totally blocked.After analysis and comparison of the rainfall processes for two debris flow events on August 13,2010 and August 18,2012,It is concluded that the accumulated precipitation triggered the debris flows increased but the critical rainfall decreased.After the 2008 Wenchuan earthquake,an abundance of loose co-seismic material sources were present in the main channel and branch channel of Yongjia gully.According to detailed site investigations,the active paths of different debris flows were not consistent.The debris flow on August 18,2012 was mainly occurred in the No.1 branch,which shows that erosion width of the channel is getting narrower and the accumulation thickness is first increased and then decreased with the increase of distance from the main channel outlet.Moreover,the particle size distribution of the debris is random in the channel.In addition,this paper also analyzed the river-blocked probability of Yongjiagou debris flows under the different rainfall frequency.The results indicate that Yongjiagou debris flow event could cause river damming when rainfall frequency greater than 20% of it’s return period,even cause the river completely blocked.更多还原