甘肃岷县永光1^(#)流滑型黄土滑坡的远程滑动特征

Long-runout characteristics of the Yongguang 1#loess flowslide in Minxian County,Gansu Province

流滑型黄土滑坡是黄土地区沿沟道或斜坡远程滑动和堆积的长条状特殊类型滑坡,常造成难以预料的严重灾害。2013年7月22日7时45分,甘肃岷县漳县Ms6.6级地震诱发的岷县永光1^(#)滑坡体积约23×10^(4)m^(3),造成12人遇难。滑坡前后缘高差175 m,总长度1030 m,高长比值为0.17,属远程滑坡。通过现场调查和对滑动过程观察资料的综合分析,探讨了其滑动过程特征、不同部位的滑速及变化情况,分析了滑动机理。受地震作用促发和地形条件等影响,永光1^(#)滑坡经历了2次加速—减速的复杂滑动过程,滑坡首先在前部平台区整体滑动50~130 m,前缘约6×10^(4)m^(3)滑体再沿前部沟道滑动740 m,最大滑距达870 m,滑动总历时约7 h,最大滑速约10.6 m/s,平均滑速0.034 m/s。永光1^(#)滑坡由地震和前期降水耦合作用形成,地震前大量降水的入渗和软化,滑动过程中高含水率滑带土产生高孔隙水压力,甚至导致液化发生,圈闭的沟道地形和滑带土的低渗透性,使孔隙水压力消散非常缓慢,在全滑程中滑带土摩阻力大幅降低,持速效应明显,是永光1^(#)滑坡远程滑动的主要原因。

Flowslide in loessic regions,characterized by their elongated shape and tendency to slide and accumulate along channels or gentle hillslopes,frequently lead to devastating and unpredictable disasters.The Yongguang 1^(#)flowslide in Minxian County,Gansu Province,caused by the Minxian-Zhangxian Ms6.6 earthquake at 7:45AM on July 22,2013,claimed twelve lives and had a volume of approximately 23×10^(4)m^(3).The landslide had a vertical difference of 175m between its front and rear edges,a total length of 1030 m,and a ratio of 0.17,classifying it as a long-runout landslide.This paper explored the characteristics of the sliding process and the sliding velocities of different portions of the flowslide through field survey and a comprehensive analysis of the observation data of the sliding process,while also analyzing the sliding mechanism.Triggered by earthquake,the runout process of the flowslide has been affected by local terrain.The flowslide experienced two complex sliding stages of acceleration and deceleration.Initially,the landslide slid as a whole in the front platform area for 50 to 130 m,and then the front sliding body with an volume of about 6×10^(4)m^(3)continued to slide along the front channel for 740 m,resulting in a maximum runout distance of 870 m.The entire sliding process lasted about 7 hours,with a maximum sliding speed of approximately 10.6 m/s,and an average sliding speed of 0.034 m/s.The formation of the Yongguang 1^(#)landslide was influenced by the coupled effects of seismic activity and early-precipitation.The earthquake,preceded by heavy rainfall,led to infiltration and softening of the soil.During the sliding process,the high water content in the sliding zone generated high pore water pressure,and in some cases,liquefaction occurred.The channel-shaped topography and low permeability of the sliding zone soil caused a very slow dissipation of pore water pressure,resulting in a significant reduction in frictional resistance in the sliding zone soil throughout the entire sliding process,with a noticeable velocity-sustaining effect.These factors are the primary reasons for the long-runout of the Yongguang 1^(#)landslide.