文家沟抛射型高速滑坡全程运动机理研究

STUDY ON THE MOVEMENT MECHANISM OF WENJIAGOU HIGH SPEED EJECTION LANDSLIDE

5·12汶川大地震期间,绵竹市清平乡文家沟发生了大型高速滑坡。本文在系统分析文家沟滑坡区的地质条件和滑体运动特征的基础上,提出了文家沟滑坡是受地震力和滑坡地面震动力共同作用的失稳启动模式,并将滑坡全程运动划分为启程震动抛射、飞行铲刮、撞击转向堆积和停积4个阶段。分析和计算表明:文家沟滑坡体在失稳启程阶段所受的地震力和滑坡地面震动力的合力方向大致为285°,这与滑体启程抛射的运动方向基本一致;同时,计算得出滑坡体在4个阶段的运动速度分别为115.64 m·s-1、69.38 m·s-1、41.6 m·s-1和20.8 m·s-1,对应的运动时间为11.8 s、8.6 s、24.0 s、48.1 s。据此得出,文家沟滑坡全程运动的持续时间约为92.5 s,这与当地幸存者估计的1分多钟的运动时间比较接近。研究表明,文家沟滑坡的启程抛射和高速飞行的运动特征,可以将滑体的高位势能充分转化成动能,是促使滑体高速运动的关键。

A huge high-speed landslide occurred in Wenjiagou of Qingping township,Mianzhu city,during the 5.12 Wenchuan earthquake.By systematical analysis of the geologic conditions and the landslide movement characteristics,the initiation breaking and instability occurring model is proposed regarding the effects of earthquake and landslide ground vibration.Then,the processes of rock mass movement is classified as four stages which include ejecting,flying and scraping,collision and direction altering,stopping and accumulating stages.Considering the earthquake and landslide ground shaking forces,the total force direction is 285°and approximately equals to the landslide initiation direction.Furthermore,the average velocity and time corresponding with the movement mass in each stage are calculated.The average velocity is 115.64 m·s-1,69.38 m·s-1,41.6 m·s-1,20.8 m·s-1 and the respective sub-total time is 11.8 s,8.6 s,24.0 s,48.1 s for the ejecting to stopping and accumulating stages,respectively.The total time of the landslide movement is 92.5 s,almost same as more than 1 minute estimated by the survival inhabitants.The results show that the main reason that cause Wenjiagou landslide to move with high speed is the effect of ejecting and flying,which transfer the gravitational potential energy to kinetic energy completely.