| 摘要: |
| 近年来，许多学者利用现场地震监测或数值试验来研究斜坡的地震响应，然而不同斜坡往往存在不同类型的地貌单元，其动力响应机制往往也存在很大差异。本文依托海原大地震区域，基于室内试验、现场波速测试等方法，运用有限元数值模拟技术对海原大地震影响范围内不同地貌单元的斜坡的动力响应进行了研究。结果表明：黄土塬具有高程放大效应，在同一高程水平面上，且距坡面一定范围内时越趋近坡面斜坡动力放大系数（peak ground acceleration amplification coefficient，PGA放大系数）越大；对比不同类型的地貌单元，地层结构相同的斜坡其响应规律一致，但在古土壤层其PGA放大效应会减弱。模型分析较好地揭示了人工合成地震波作用下黄土高原斜坡的动力放大效应，可为不同地貌单元地震诱发的地质灾害的风险评价和防灾减灾提供有益的借鉴与参考。 |
| 关键词: 不同地貌 地震动 有限元 数值模拟 放大效应 |
| DOI：10.7515/JEE212032 |
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| 基金项目:国家重点研发计划项目（2018YFC1504700） |
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| Dynamic response of loess slopes in different geomorphic units in Haiyuan Seismic Zone |
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WU Meng, GU Tianfeng, GU Qi, SONG Zhijie, ZONG Hua
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State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
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| Abstract: |
| Background, aim, and scope The Haiyuan earthquake in 1920 triggered various geological disasters, among which, landslides are most destructive, which pose threat to hundreds of thousands of people’s lives. While the earthquake force is the final cause of the damages. Therefore, the dynamic response mechanism is of great research significance to the exploration of the ground motion mechanism of landslides. In recent years, field seismic monitoring or numerical experiments are applied to investigate the seismic response mechanisms of specific slopes. However, these mechanisms haven’t been fully clarified due to the high diversity of geomorphic units in the Haiyuan earthquake area. Hence, this paper aims to further explore the amplification effect of ground vibration parameters of different geomorphic units in loess areas by establishing numerical models of several slopes. Materials and methods In this study, the finite element numerical simulation technology was applied based on laboratory test, artificial seismic waves, loess wave velocity test, GDS test and so on to investigate the slope dynamic response of different geomorphic units within the influence range of the Haiyuan earthquake. Results The results show that the soil sample was light yellow, with large pore space, loose structure and vertical joints, and it contained a small amount of calcareous nodules, showing strong collapsibility. The monitoring points at the bottom of the slope were consistent with the waveform of the input seismic wave; the acceleration time history curve of each monitoring point was obtained, and thus the dynamic amplification factor of each monitoring point was calculated. Discussion According to the dynamic amplification coefficient curves of slope b and slope c, the amplification coefficients law of slopes of different geomorphic units were discussed. According to the dynamic amplification coefficient curves of slope a, the dynamic response laws of slopes under different stratigraphic conditions were discussed. The dynamic amplification curves of slopes of three different geomorphic units were compared to identify the laws of their prograde amplification effects. Conclusions The results show that the elevation amplification effect of the loess tableland was obvious, and the PGA amplification coefficient increased with the approach to the slope in a certain range of the same elevation level. Compared with different types of geomorphic units, the response of slopes with the same stratigraphic structure was consistent, but the PGA amplification effect was weakened in the paleosol. Recommendations and perspectives The model analysis has revealed the dynamic amplification effect of artificial seismic waves on the slopes of the Loess Plateau, expecting to provide reference for the risk assessment, as well as prevention and mitigation of geological disasters in different geomorphic units. |
| Key words: different geomorphology ground motion finite element numerical simulation amplification effect |
