地震和降雨耦合作用下黄土边坡动力响应的振动台试验研究
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摘要
2013年岷漳Ms6.6级地震诱发的永光村泥流状滑坡表明,单一因素下稳定的黄土边坡在地震和降雨耦合作用下会诱发严重的岩土灾害。因此,基于防御与减轻地震灾害的现实需求,开展了地震和降雨耦合作用下黄土边坡振动台模型试验,通过加载卓越频率差异较大的原始波和压缩波,研究了地震和降雨耦合作用下黄土边坡的动力响应特征。试验结果表明:边坡动力作用过程,土体微结构不断损伤演化,土体动力参数——共振频率与阻尼比随动载强度增大不断调整变化,从而引起边坡不同部位加速度响应特征(频谱、幅度)的变化。PGA放大效应取决于边坡自振频率与荷载主频接近程度,当二者愈接近,放大效应越明显,反之放大效应越弱甚至响应衰减(放大系数小于1)。根据边坡模型宏观变形以及相关物理量的变化特征,地震和降雨耦合作用下的边坡失稳破坏过程可划分为:弹性动变形阶段、残余变形快速增加阶段、液化滑移阶段,不同阶段边坡动力响应各具特点。
The muddy loess landslide in Yongguang village induced by the Minxian-Zhangxian Ms 6.6 earthquake shows that the loess slope being stable under the action of single factor will induce severe disaster under the coupling effects of earthquakes and rainfalls. Therefore, based on the realistic demand of defense and mitigation of earthquake disasters, the shake table model tests on loess slopes under the coupling effects of earthquakes and rainfalls are carried out to study their dynamic response characteristics. The test results show that the dynamic process of slopes is the process of continuous damage of loess microstructure, and the natural frequency and the damping ratio of soil mass continuously change with the increase of load intensity so as to cause the changes of the acceleration response characteristics(spectrum and amplitude) of different parts of the slopes. The PGA amplification effect of loess slopes depends on the close extent of natural frequency of slopes and load frequency. When the two are closer, the amplification effect is more obvious. On the contrary, the amplification effect is weakened and even is reduced(The amplification factor is less than 1). According to the macroscopic deformation and related physical changes, the instability failure process of slopes under the coupling effects of earthquakes and rainfalls can be divided into the following stages: elastic dynamic deformation stage, rapidly increasing residual deformation stage and liquefaction sliding stage, and the dynamic response of slopes at different stages has its own characteristics.
The muddy loess landslide in Yongguang village induced by the Minxian-Zhangxian Ms 6.6 earthquake shows that the loess slope being stable under the action of single factor will induce severe disaster under the coupling effects of earthquakes and rainfalls. Therefore, based on the realistic demand of defense and mitigation of earthquake disasters, the shake table model tests on loess slopes under the coupling effects of earthquakes and rainfalls are carried out to study their dynamic response characteristics. The test results show that the dynamic process of slopes is the process of continuous damage of loess microstructure, and the natural frequency and the damping ratio of soil mass continuously change with the increase of load intensity so as to cause the changes of the acceleration response characteristics(spectrum and amplitude) of different parts of the slopes. The PGA amplification effect of loess slopes depends on the close extent of natural frequency of slopes and load frequency. When the two are closer, the amplification effect is more obvious. On the contrary, the amplification effect is weakened and even is reduced(The amplification factor is less than 1). According to the macroscopic deformation and related physical changes, the instability failure process of slopes under the coupling effects of earthquakes and rainfalls can be divided into the following stages: elastic dynamic deformation stage, rapidly increasing residual deformation stage and liquefaction sliding stage, and the dynamic response of slopes at different stages has its own characteristics.
引文
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[9]蒋良潍,姚令侃,吴伟,等.传递函数分析在边坡振动台模型试验的应用探讨[J].岩土力学,2010,31(5):1368–1374.(JIANG Liang-wei,YAO Ling-kan,WU Wei,et al.Application of transfer function analysis on slope shaking table model test[J].Rock and Soil Mechanics,2010,31(5):1368–1374.(in Chinese))
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[11]WANG L M,WU Z J,XIA K.Effects of site conditions on earthquake ground motion and their applications in seismic design in loess region[J].Journal Mountain Science,2017,14(6):1185–1193.
[12]栾茂田,李顺群,杨庆.非饱和土的基质吸力和张力吸力[J].岩土工程学报,2006,28(7):863–868.(LUAN Mao-tian,LI Shun-qun,YANG Qing.Study on matrix suction and tension suction of unsaturated soils[J].Journal of Geotechnical Engineering,2006,28(7):863–868.(in Chinese))
[2]徐舜华,吴志坚,孙军杰,等.岷县漳县6.6级地震典型滑坡特征及其诱发机制[J].地震工程学报,2013,35(3):471–476.(XU Shun-hua,WU Zhi-jian,SUN Jun-jie,et al.Typical landslide characteristics and induced mechanism of the Ms6.6 earthquake in Zhang County,Minxian County[J].Earthquake Engineering,2013,35(3):471–476.(in Chinese))
[3]吴志坚,王兰民,陈拓,等.汶川地震远场黄土场地地震动场地放大效应机制研究[J].岩土力学,2012,33(12):3736–3740.(WU Zhi-jian,WANG Lan-min,CHEN Tuo,et al.Study on the magnifying mechanism of earthquake ground in the far field loess site of Wenchuan Earthquake[J].Rock and Soil Mechanics,2012,33(12):3736–3740.(in Chinese))
[4]言志信,曹小红,张刘平,等.地震作用下黄土边坡动力响应数值分析[J].岩土力学,2011,32(增刊2):610–614.(YAN Zhi-xing,CAO Xiao-hong,LIU Ping,et al.Numerical analysis of dynamic response of loess slope under earthquake[J].Rock and Soil Mechanics,2011,32(S2):610–614.(in Chinese))
[5]谢定义,冯志焱.对非饱和土有效应力研究中若干基本观点的思辨[J].岩土工程学,2006,28(2):170–173.(XIE Ding-yi,FENG Zhi-yan.Some basic ideas on the study of effective stress in unsaturated soils[J].Geotechnical Engineering,2006,28(2):170–173.(in Chinese))
[6]吴志坚,雷天,陈豫津,等.黄土斜坡变形失稳破坏特征的振动台模型试验[J].上海交通大学学报,2015(7):940–945.(WU Zhi-jian,CHEN Yu-jin,WANG Ping,et al.Study on the instability characteristics of loess slope based on shaking table model test[J].Shanghai Jiao Tong University Journal,2015(7):940–945.(in Chinese))
[7]邵生俊,周飞飞,龙吉勇.原状黄土结构性及其定量化参数研究[J].岩土工程学报,2004,26(4):531–536.(SHAO Sheng-jun,ZHOU Fei-fei,LONG Ji-yong.Structural and Quantitative Parameters of Undisturbed Loess[J].Journal of Geotechnical Engineering,2004,26(4):531–536.(in Chinese))
[8]林皋,朱彤,林蓓.结构动力模型试验的相似技巧[J].大连理工大学学报,2000(1):1–8.(LIN Gao,ZHU Tong,LIN Bei.Similar techniques for structural dynamic model test[J].Journal of Dalian University of Technology,2000(1):1–8.(in Chinese))
[9]蒋良潍,姚令侃,吴伟,等.传递函数分析在边坡振动台模型试验的应用探讨[J].岩土力学,2010,31(5):1368–1374.(JIANG Liang-wei,YAO Ling-kan,WU Wei,et al.Application of transfer function analysis on slope shaking table model test[J].Rock and Soil Mechanics,2010,31(5):1368–1374.(in Chinese))
[10]WANG L M,WU Z J.Influence of site condition on seismic amplification effects during the Wenchuan earthquake[J].Journal of Civil,Architectural&Environmental Engineering,2010,32(S2):175–178.
[11]WANG L M,WU Z J,XIA K.Effects of site conditions on earthquake ground motion and their applications in seismic design in loess region[J].Journal Mountain Science,2017,14(6):1185–1193.
[12]栾茂田,李顺群,杨庆.非饱和土的基质吸力和张力吸力[J].岩土工程学报,2006,28(7):863–868.(LUAN Mao-tian,LI Shun-qun,YANG Qing.Study on matrix suction and tension suction of unsaturated soils[J].Journal of Geotechnical Engineering,2006,28(7):863–868.(in Chinese))