云南鲁甸MS6.5地震红石岩滑坡稳定性的数值模拟

doi:10.3969/j.issn.0253-4967.2015.22

摘要/Abstract

摘要：

2014年8月3日鲁甸M_S6.5地震触发了大量的滑坡崩塌, 其中, 位于鲁甸县李家山村和巧家县红石岩村交界处的牛栏江干流北岸的红石岩滑坡规模巨大, 与此处位于左岸的红石岩古滑坡体的前缘部分一起堵塞了牛栏江而形成高达120m、体积达1 200×10⁴m³的大型堰塞体。通过震后开展的野外实地调查, 获得了红石岩滑坡发生处的地形地貌、地质构造、岩体结构及物质组成等资料。以这些第一手资料为基础, 构建了红石岩滑坡的边坡模型, 并应用边坡稳定性分析软件GeoStudio中Slope/W模块分别计算了红石岩滑坡体震前坡体安全系数和地震作用下的坡体安全系数。结果表明, 红石岩滑坡体发生处的坡体安全系数在地震前为1.450, 处于相对稳定状态, 而鲁甸地震的地震动作用则使坡体的安全系数降低至0.962, 直接导致红石岩坡体的失稳。文中进一步讨论了坡体滑动面的存在与否对坡体稳定性的影响: 安全系数计算的结果表明, 在中强地震作用下, 先存滑动面的存在是导致大型滑坡形成的重要条件;对于高陡岩质边坡, 如果没有先存滑动面, 只可能形成浅表性滑坡。

关键词: 鲁甸M_S6.5地震, 红石岩滑坡, 滑动面, 安全系数, 数值模拟

Abstract:

Although the landslides triggered during earthquake events are common phenomena in the southwest China, the occurrence of the Hongshiyan landslide triggered by the M_S6.5 Ludian earthquake in 2014 is attractive for its giant volume which exceeds ten million cubic meters. The Hongshiyan landslide formed a quake lake and inundated a village. Based on the geological and geomophological data obtained through the immediate field investigation after the earthquake, we build the Hongshiyan slope model and at the same time, we apply numerical simulation to study the landslide formation. Result indicates that the Hongshiyan slope was at safe conditions with the Factor of safety (Fs) value greater than 1, but the ground seismic motion during the Ludian earthquake lowered its Fs to a value smaller than 1, which resulted in the occurrence of the landslide. Moreover, this study shows that an existing slip surface is important for generating a giant landslide, and steep slopes without existing slip surfaces are likely to generate shallow landslides with normal volumes.

Key words: the M_S6.5 Ludian earthquake, the Hongshiyan landslide, slip surface, Factor of safety(Fs), numerical simulation

中图分类号:

P315.9

陈晓利, 常祖峰, 王昆. 云南鲁甸M_S6.5地震红石岩滑坡稳定性的数值模拟[J]. 地震地质, 2015, 37(1): 279-290.

CHEN Xiao-li, CHANG Zu-feng, WANG Kun. NUMERICAL SIMULATION STUDY OF HONGSHIYAN LANDSLIDE TRIGGERED BY THE M_S6.5 LUDIAN EARTHQUAKE[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(1): 279-290.

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