泾阳南塬黄土滑坡冲击阶地易侵蚀层过程模拟

Impacting pocess simulation of loess landslides on the easily-eroded terrace layers at south Jingyang plateau

为探讨泾阳南塬地区黄土滑坡的高速远程的运动特征以及在运动过程中对阶地易侵蚀基层破坏迹象的产生机理。以泾阳南塬西庙店滑坡为研究对象,通过野外调查、勘探查明其运动特征,运用颗粒流离散元法模拟滑坡运动过程、机理。结果表明:滑坡运动过程中,滑体对阶地易侵蚀基层的冲击刮铲作用显著,宏观上表现为滑坡前缘地层隆起与逆冲剪断。滑坡滑动产生的振动作用使阶地粉土发生液化,液化后的粉土在超孔隙水压力作用下沿上覆土体导水通道涌出,形成显著的“涌砂”现象。滑坡运动全过程历时84 s,滑体颗粒最大运动速度36.2 m/s,最大运动距离253.2 m,具有典型的“高速”、“远程”特征。分析得到2点结论:①泾阳南塬典型高速远程黄土滑坡运动过程可分为3个阶段,即,冲击置换的加速阶段(0~2.9 s)、滑覆铲刮的减速阶段(2.9~5.7s)与堆积推覆的慢速波动阶段(5.7~84 s);②滑体速度场变化特征明显,也可划分为3个阶段,即,加速阶段(0~2.9 s)、减速阶段(2.9~5.7 s)以及慢速波动阶段(5.7~84 s)。

In order to explore the characteristics of high-speed and long-runout motion and the mechanism of the obvious signs of damage to the easily-eroded terrace layers in the course of movement in south Jingyang plateau,this paper,taking Ximiaodian landslide in south Jingyang plateau as the research object,examines its motion characteristics through the investigation and exploration in the field,and simulates the process of landslide motion by means of particle flow code(PFC).The results show that:in the sliding process,the impact and shovel scraping action of the sliding body on the easily-eroded terrace layers is significant,and the macroscopic manifestation is the uplift of the formation at the leading edge of landslide and the thrust shear.The vibration caused by landslide sliding makes the silty soil in the terrace liquefied.And the liquefied silty soil gushes out along the water channel of the overlying soil under the action of excess pore water pressure,forming a significant phenomenon of“sand gushing”.The whole process of Ximiaodian landslide lasts for 84 s,and the maximum movement speed of the sliding particles is 36.2 m/s,and the maximum movement distance is 253.2 m,which is typical of“high speed”and“long distance”.Finally,two conclusions are drawn:the typical high-speed and long-runout loess landslide movement process in south Jingyang plateau can be divided into three stages,namely,the acceleration stage of impact and replacement(0~2.9 s),the deceleration stage of sliding cover and shovel scraping(2.9~5.7 s)as well as the slow fluctuation stage of accumulation and nappe(5.7~84 s).According to the speed field characteristics of the sliding body,the sliding process can be divided into the acceleration stage(0~2.9 s),the deceleration stage(2.9~5.7 s)and the slow fluctuation stage(5.7~84 s).