中文摘要：

1920年海原大地震触发了多处典型高速远程地震黄土滑坡,本文在对西吉党家岔滑坡进行野外调研的基础上,采集了具有代表性的滑带土作为试验样品,以1940年5月18日美国帝国谷强震记录作为波动输入,利用DPRI环剪试验机,对该滑坡的发生机制进行了一系列环剪试验研究。结果表明,地震发生时,坡体潜在滑面的滑带土在强震作用下发生的＂滑动面液化＂（Sliding surface liquefaction）现象是导致高速远程滑坡形成的一个重要因素。伴随着＂滑动面液化＂过程,滑体产生了逐渐增大的剪切位移及孔隙水压力（地震力作用结束瞬间已分别达到2.03m及104kPa）,并获得了较大的速度,为高速远程滑坡的发生提供了条件。

英文摘要：

The 1920 Haiyuan Earthquake caused a great number of loess landslides, and resulted in more than 100,000 deaths. This paper investigates the Dangjiaeha landslide, a typical rapid and long run -out landslide loca- ted in Xiji County triggered by Haiyuan earthquake. Representative soils on sliding surface were collected for soil tests. By using the advanced DPRI ring shear apparatus, a series of ring shear tests were carried out to study the in- itiation mechanism of Dangjiaeha landslide under the seismic wave loading of EL - Centro Earthquake. This Earthquake occurred on May 18, 1940 in United States. The ring shear test results show that when the earthquake hap- pened, the ＂sliding surface liquefaction＂ occurred on potential sliding surface of landslide. It was an important rea- son for taking place of rapid and long run - out landslide. Meanwhile, a large shear displacement { 2.03 m } and a high pore water pressure { 104 kPa } could be generated and a high velocity could be got for the sliding mass, which supplied a necessary condition for the generation of rapid and long run - out landslide.