汶川地震区绵远河流域泥石流形成区的崩塌滑坡特征

The Characteristic of Collapse and Landslide by Wenchuan Earthquake in Debris Flow for Mative Region along the Mianyuan River Basin,China

2008年汶川地震以后,四川省绵竹市清平乡表面覆盖了大量松散堆积物,这些物源在震后的几年中易受到暴雨激发,导致大量浅层崩塌、滑坡的形成,尤其在泥石流形成区。研究泥石流形成区崩塌、滑坡特征,有助于分析滑坡向泥石流转化的特点。2010-08-13绵远河流域发生强降雨致使数十条沟暴发泥石流,在统计了研究区内20条沟泥石流形成区内的386个崩塌、滑坡后,利用野外调查及高精度遥感影像,将386个崩塌、滑坡全部解译,并利用GIS分析统计出崩塌、滑坡在坡度、坡向、高程、沟道纵坡降、地层岩性、沟壑密度因子上的分布特征,得出在海拔1 700～2 400 m范围内崩塌、滑坡密度最大;坡度是影响崩塌、滑坡分布的重要因素,随着坡度的增加密度也越来越大,>70°时极易失稳;滑坡的方向垂直于发震断层明显多于平行于发震断层;纵坡降在500‰～600‰的区间内崩塌、滑坡大量分布;石炭系灰岩出露的地层容易产生大量崩塌、滑坡,尤其在下硬上软的岩层上面;在微度水土流失的区域,崩塌、滑坡分布集中,因此要加强该区域的监测预警。

After the 2008 Wenchuan earthquake, an abundance of loose co-seismic material sources were present in the Qingping town Mianzhu city of Sichuan province, where in later years served as source material for rainfall-in- duced shallow landslides, especially in forming region of debris flow. The characteristic of collapse and landslide in forming region of debris flow can help to analyze landslide transform to debris flow. A heavy rain occurred on Au- gust 13th along Mianyuan River,where a number of debris flow occurred. A spatial datal^ase,which included 386 landslides in forming region of 20 debris flows, was developed and analyzed using high precision image and field survey within the Mianyuan River basin. We also used GIS to census the rule of distribution of landslides in gradi- ent, slope direction, elevation, and channel gradient, the lithology of stratum and drainage density factors. After analysis of the statistics in six evaluation factors, we find that the largest landslide density in the 1 700 - 2 400 m, the slope is the important factor of landslide distribution, with the increase of slope , the will increase. scope of density When landslide slope 〉 70°, it can is instabiliy. The aspect of perpendicular of the landslide significantly more than parallel to the seism genie fauhs;a lot of collapse landslides highly concentrated in the 500‰ -600‰ slope cially rosion of gully;the carboniferous strata of limestone can easily produce the large amount of collapse landslide, espe- in the soft soil above the hard bedrock zone. The landslide concentrating distribute in micro degrees of soil e- area, so we should strengthen the monitoring and warning system in this area.