“5·12”地震重灾区茂县竹包头沟泥石流特征及其防治对策

The Feature and Prevention Methods of the Zhubaotou Gully Debris Flows of Maoxian in Severe Earthquake Disaster Area of "5·12" Earthquake

"5.12"汶川地震不仅直接造成了巨大的人员和财产损失,同时还诱发了大量的崩塌、滑坡、泥石流等次生山地灾害。崩塌、滑坡直接为泥石流活动提供了丰富的松散固体物质,再加上在地震荷载的多次往复作用下,山体的整体性遭到破坏,大量坡体失稳,岩体破坏,使这些泥石流沟在今后较长一段时间内处于活跃期。2008年6月18日,位于重震区的茂县东兴乡竹包头沟暴发泥石流,将主河湔江堵断随后溃决,对临近的"302"省道造成了较为严重的危害。该沟上游段沟床比降大,岸坡较陡,流域内出露的岩石以千枚岩为主,易风化破碎,在地震中形成许多崩塌和滑坡,加之流域降水集且多局地性暴雨,有利于泥石流的发育。在调查访问的基础上,估算该次泥石流的容重为2.0 g/cm3,为高容重粘性泥石流。计算出其流速在10 m/s以上,流量约300 m3/s,总规模为1×105m3。竹包头沟泥石流固体物质的主要来源为地震引发的崩塌和滑坡堆积物,根据遥感资料测算,总方量达3×1010m3以上,再次暴发泥石流的可能性很大。为减弱泥石流活动,减轻泥石流造成的损失,提出以下应对措施:以生物防治措施为主,减少泥石流物源;加强监测,及时警报,减轻泥石流危害;普及泥石流知识,提高防灾减灾能力。

The Wenchuan May 12th Earthquake has caused heavy casualties and property losses immediately,and induced a mass of secondary mountainous disasters such as collapse,landslide and debris flow.Collapse and landslide provide abundant incompact solid matter for movement of debris flow directly,plus under action of reciprocating movement of earthquake load time after time,so integrity of mountains is demolished,a great deal of slope possess instability,and rock mass is destroyed,which makes the debris flow ravines be active in a long period in the future.Debris flow broke out in Zhubaotou Ravine in Dongxing Township,Maoxian County on June 18th,2008,plugged up the main stream Jianjiang River and burst later,which brought serious harm to the provincial highway Line 302 nearby.Gradient of this gully bed of the upper reaches is large,and bank slope is relatively steep.Exposed rock in the drainage basin is mostly phyllite,prone to airslake and break up,which gives birth to much collapse and landslide in the earthquake.Additionally,precipitation is centralized in the drainage basin and much of them is rainstorm,so it is propitious to development of debris flow.On basis of investigation and visitation,it is estimated bulk volume of this debris flow is 2.0 g/cm3,belong to glutinous,high-bulk volume debris flow.It is calculated its velocity of flow is above 10 m/s,flux is about 300 m3/s,and total volume is 1×105 m3.Primary source of solid matter of the debris flow in Zhubaotou Ravine is deposit of collapse and landslide provoked by the earthquake.It is measured by RS data that total volume is above 3×1010 m3,so it has much possibility to break out debris flow again.In order to weaken activity of debris flow,and alleviate the damage caused by it,the following solutions are put forward that biological control is the chief measure,to reduce matter source of debris flow;monitoring should be strengthened,and alarm in time,to mitigate the damage;knowledge of debris flow be popularized,and improve capability of disaster prevention and mitigation.