岷县漳县6.6级地震永光村滑坡致灾机制分析

2013年7月22日甘肃省定西市岷县漳县MS6.6级地震,诱发了大量黄土滑坡和崩塌灾害。基于对岷县梅川镇永光村西侧泥流状黄土滑坡的现场勘察、探井取样和高密度面波勘探,得到了该滑坡的地形条件和土层分布特点。通过对滑坡体土样进行室内动三轴液化试验,验证了该滑坡土体在地震作用下发生液化的可能。结合动力有限元法和强度折减法,分析了该滑坡在地震作用下的动力响应特征和动力稳定性的影响因素。结果表明:震前的持续强降雨,导致滑坡体表层黄土含水率升高,抗剪强度降低,在强地震荷载作用下,黄土层之间存在拉应力效应,表层土体发生液化,造成该斜坡失稳瞬间发生,发生长距离滑移。

Disaster-causing mechanism of Yongguang landslide under Minxian-Zhangxian Ms6.6 Earthquake

The Minxian-Zhangxian MS6.6 earthquake induced a large number of loess landslides and collapses on July 22, 2013. Based on the field borehole survey, soil sampling and surface wave investigation, the topography and distribution of soil layers of the west Yongguang loess landslide are identified. Moreover, the liquefaction probability of the landslide loess is proven through dynamic triaxial liquefaction tests. The dynamic response characteristics and stability influence factors of the landslide under strong earthquake effect are analyzed combining the dynamic finite element method and the strength reduction method. The results show that the water content increases and shear strength decreases at the loess on the slope surface because of heavy rain before the earthquake, and tensile stress and liquefaction occur in the surface of loess slope, which causes the collapse instantaneously and long sliding distance.