都江堰市龙池镇“8·13”蜂桶岩泥石流灾害特征

Features of Fengtongyan debris flow hazard on August 13,2010 in Longchi town of Dujiangyan,Sichuan,China

蜂桶岩泥石流是汶川地震灾区都江堰市龙池镇2010年"8.13"泥石流灾害中的新增灾害点之一。以野外调查资料和室内实验数据为基础,分析了蜂桶岩泥石流的成灾条件、过程及特征。蜂桶岩沟流域内地震产生的部分松散固体物质在降水带动下向沟下游流动,侵蚀地表形成洪水沟。在8月13日的强降雨作用下,大量坡体上的松散固体物质随水流汇集到洪水沟,与沟道内的松散堆积物质一起迅速向下流动形成泥石流。激发蜂桶岩泥石流的1h降雨量为53.8mm,8月13日全天总降雨量为209.8mm,降雨频率约为十年一遇。"8.13"蜂桶岩泥石流容重为2.0g/cm3,泥石流屈服应力为4999Pa,洪峰流量为104m3/s,冲出物总体积为7.4×104 m3。蜂桶岩沟在发生"8.13"泥石流后沟道深切,流域内还存有松散固体物源,具备再次发生泥石流的条件,沟口区域不再适宜作为居民建设用地。

The Fengtongyan debris flow is one of the new hazards occurred on August 13, 2010 in Longchi of Dujiangyan city in the Wenchuan earthquake area in Sichuan of China. Based on the site investigation and experiment data, the authors analyze the formation conditions, disaster processes and characteristics of the Fengtongyan debris flow in this paper. Driven by the precipitation, some loose solid materials of the Fengtongyan valley flowed downstream, eroding the surface to form a flood ditch. The ＂8 · 13＂ rainstorm induced a large number of loose solid materials on the slope to collect in the flood ditch, and rapidly flowed downstream with the loose solid materials within the flood ditch to form the debris flow. The hour precipitation triggering the debris flow is 53.8 mm and the total precipitation is 209.8 mm on August 13, 2010. This rainfall return period is 10 years. The bulk density is 2.0 g/cm3 , the yield stress is 4999 Pa, the discharge is 104 m3/s, and the debris flow scale is 7.4 × 104 ma. The channel of the Fengtongyan gully is deep after the ＂8 · 13＂ debris flow, and there are still some loose solid materials in the valley. These are conditions to form debris flows again, so the area at the mouth of the Fengtongyan gully is not suitable for residential construction.