汶川地震后四川省安县黄洞子沟泥石流特征

CHARACTERISTIC OF DEBRIS FLOW IN HUANGDONGZI GULLY OF SICHUAN PROVINCE AFTER THE WENCHUAN EARTHQUAKE

2008年5月12日汶川地震诱发了黄洞子沟流域规模巨大的大光包滑坡,部分滑体前冲堆积于沟道内,直接为后期泥石流的形成提供了丰富的松散固体物质,改变了黄洞子沟泥石流形成条件,使黄洞子沟从一条非泥石流沟演变成了一条高频泥石流沟。震后黄洞子沟几乎每年雨季都会暴发不同规模的泥石流,其中以2013年"7·09"泥石流灾害规模和危害最大。本文着重分析了黄洞子沟泥石流形成特征,并从地形、降水和地质三个方面将黄洞子沟和文家沟进行对比,得出了物源堆积体颗粒粒径与泥石流形成的关系。

The 2008 Wenchuan Earthquake induced a huge scale landslide in Huangdongzi gully, part of the sliding mass accumulation in the channel, provided abundant loose materials to the later formation of debris flow, changed the debris flow formation conditions of Huangdongzi gully, and made it from a non-debris flow gully to a high frequency of debris flow gully. Gaochuan village is near the fault, and the seismic esthesia is strong. After earthquake, in every rainy season Huangdongzi gully had different scale of debris flow. On September 24, 2008, July 17, 2009, August 13, 2010, August 17,2012, July 9, 2013, debris flow happened, and the ＂7.09＂ debris flow had the largest scale and damage. This paper focused on the analysis of the debris flow formation characteristics of Huangdongzi gully, and compared Huangdongzi gully with Wenjia gully from terrain, rainfall and geological, and finally obtained the relation of the particle diameter and the formation of debris flow. The impact of earthquake on the terrain conditions mainly included two aspects： the destruction of the slope vegetation and blocking channel to change longitudinal ratio. Huangdongzi gully and Wenjia gully are similar in terms of terrain, and are conducive to the formation of debris flow. Both Qingping town of Mianzhu City and Gaochuan village of An county are in heavy rain area, and rainfall scale in Huangdongzi gully is greater than that in Wenjia gully. The water source and water dynamic condition of Huangdongzi gully are more favorable for the formation of the large scale debris flow disaster. The landslide accumulation in Huangdongzi gully is mainly based on the large grain size, and Wenjia gully is mainly based on the small grain size. Thus, debris flow development level and scale in Huangdongzi gully is smaller than that in Wenjia gully. The results showed that particle size played an important role in the formation of debris flow, more content of coarse particle（24cm） was not conducive to the formation of debris flow, but more fine particle（5cm） was benefit to the formation of debris flow. Huangdongzi gully still had a lot of landslide clastic accumulation which could develop to debris flow, thus we should be vigilant in heavy rain season.