黄土丘陵河谷场地地震动特征研究
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摘要
研究黄土丘陵河谷场地在地震作用下强地面运动特征的变化情况,可以揭示强震对该类场地上震害的触发机理。结合黄土高原的地貌特征,建立具有代表性的动力数值分析模型,通过输入不同幅值、频谱特性和持续时间的地震波,对起伏地形和覆盖黄土层共同影响下的黄土河谷场地进行地震反应分析。结果表明:黄土层和地形耦合作用控制了地表的PGA变化,使其趋于复杂,在同一输入波不同振幅作用下,与基岩河谷各测点相比,黄土覆盖河谷场地的地震动频谱幅值均有所增加,并且频谱主峰均向高频移动。在不同地震波输入下,场地不同部位的固有频率受地形高程和土层影响;而地震动大小和频谱幅值不仅与场地的基本频谱和地形起伏有关,也与输入地震波的频谱成分相关。输入波PGA与地震频谱特征都不变时,同一场地输出的地震频谱形状具有相似的特征,随着地震持时增长,能量向场地基本频率附近集中,从而可能导致场地上相应频率建筑物震动幅值增加,造成累积破坏。
The trigger for seismic damage may be determined by researching the characteristics of strong ground motion in loess hill valleys under earthquake action.In this paper,considering the geomorphic characteristics of the Loess Plateau,typical models of dynamic numerical analysis are established.In a valley site influenced by rugged terrain and a loess covering layer,the seismic response was analyzed by inputting seismic waves with different amplitudes,frequency spectrum characteristics,and duration.The results show that the coupling action of the soil layer and terrain controls the PGAchange on the ground surface and that the change trend is complex.Under the input of the same wave with a different amplitude and compared with monitoring points in the bedrock valley,the spectrum amplitude of the ground motion at the loess-covered valley points increased,and the peak moved to a high frequency.Under the input of different seismic waves,the natural frequencies of different parts of the site were influenced by the terrain and the soil layers;the size and amplitude of the ground motion frequency spectrum was not only related to the natural frequency spectrum of the site and topographic change,but also to the spectral components of the input seismic wave.At the same site,with the same PGA and seismic spectrum characteristics of the input wave,the output seismic spectrum shape showed similar characteristics.As the seismic duration increased,the earthquake energy was concentrated in the field near the natural frequency,which may lead to an increase in the vibration amplitude of buildings with a corresponding frequency.
The trigger for seismic damage may be determined by researching the characteristics of strong ground motion in loess hill valleys under earthquake action.In this paper,considering the geomorphic characteristics of the Loess Plateau,typical models of dynamic numerical analysis are established.In a valley site influenced by rugged terrain and a loess covering layer,the seismic response was analyzed by inputting seismic waves with different amplitudes,frequency spectrum characteristics,and duration.The results show that the coupling action of the soil layer and terrain controls the PGAchange on the ground surface and that the change trend is complex.Under the input of the same wave with a different amplitude and compared with monitoring points in the bedrock valley,the spectrum amplitude of the ground motion at the loess-covered valley points increased,and the peak moved to a high frequency.Under the input of different seismic waves,the natural frequencies of different parts of the site were influenced by the terrain and the soil layers;the size and amplitude of the ground motion frequency spectrum was not only related to the natural frequency spectrum of the site and topographic change,but also to the spectral components of the input seismic wave.At the same site,with the same PGA and seismic spectrum characteristics of the input wave,the output seismic spectrum shape showed similar characteristics.As the seismic duration increased,the earthquake energy was concentrated in the field near the natural frequency,which may lead to an increase in the vibration amplitude of buildings with a corresponding frequency.
引文
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[12]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 of Mechanism of Site Amplification Effects on Ground Motion in Far Field Loess during Wenchuan MS8.0 Earthquake[J].Rock and Soil Mechanics,2012,33(12):3736-3740.(in Chinese)
[13]Louis Geli,Pierre-Yves Bard,Beatrice Jullien.The Effect of Topography on Earthquake Ground Motion:A Review and New Results[J].Bulletin of the Seismological Society of America,1988,78(1):42-63.
[14]王伟.地震动的山体地形效应研究[D].哈尔滨:中国地震局工程力学研究所,2011.WANG Wei.Effect of Hill Topography on the Ground Mote[D].Harbin:Institute of Engineering Mechanics,CEA,2011.(in Chinese)
[15]王海云.土层场地的放大作用随深度的变化规律研究——以金银岛岩土台阵为例[J].地球物理学报,2014,37(3):1498-1509.WANG Hai-yun.Study on Variation of Soil Site Amplification with Depth:A Case at Treasure Island Geotechnical Array,San Franciso Bay[J].Chinese Journal of Geophysics,2014,37(3):1498-1509.(in Chinese)
[2]王兰民,孙军杰.黄土高原城镇建设中的地震安全问题[J].地震工程与工程振动,2014(4):115-122.WANG Lan-min,SUN Jun-jie.Seismic Safety Issues in the Process of Urban Development in Loess Plateau[J].Earthquake Engineering and Engineering Dynamics,2014,34(4):115-122.(in Chinese)
[3]石玉成,卢育霞.汶川8.0级地震甘肃灾区震害特点及恢复重建对策[J].地震工程学报,2009,31(1):1-7.SHI Yu-cheng,LU Yu-xia.The Damage Features of Wenchuan8.0Earthquake in Gansu Disaster Area and Countermeasures of Reconstruction[J].China Earthquake Engineering Journal,2009,31(1):1-7.(in Chinese)
[4]王兰民,吴志坚.岷县漳县6.6级地震震害特征及其启示[J].地震工程学报,2013,35(3):401-412.WANG Lan-min,WU Zhi-jian.Earthquake Damage Characteristics of the Minxian-Zhangxian MS6.6Earthquake and Its Lessons[J].China Earthquake Engineering Journal,2013,35(3):401-402.(in Chinese)
[5]Bouchon M,Barker J S.Seismic Response of a Hill:The Example of Tarzana,California[J].B S S A,1996,86(1A):66-72.
[6]卢育霞,刘琨,姚凯,等.甘肃文县上城台地的地震记录分析[J].西北地震学报,2011,33(增刊):393-397.LU Yu-xia,LIU Kun,YAO Kai,et al.Analysis on Seismic Records Observed on Shangcheng Platform in Wenxian,Gansu Province[J].China Earthquake Engineering Journal,2011,33(Supp):393-397.(in Chinese)
[7]王伟,刘必灯,刘欣,等.基于汶川MS8.0地震强震动记录的山体地形效应分析[J].地震学报,2015(3):452-462.WANG Wei,LIU Bi-deng,LIU Xin,et al.Analysis on the Hill Topography Effect Based on the Strong Ground Motion Records of Wenchuan MS8.0Earthquake[J].Acta Seismologica Sinica,2015,37(3):452-462.(in Chinese)
[8]刘琨.地形条件对地震动参数的影响研究[D].兰州:中国地震局兰州地震研究所,2010.LIU Kun.Effect of Topography on Ground Motion Parameters[D].Lanzhou:Institute of Seismology,CEA,2010.(in Chinese)
[9]张孝波,景立平,肖文海.大型河谷场地地震动特性研究[J].防灾减灾工程学报,2010,30(6):644-649.ZHANG Xiao-bo,JING Li-ping,XIAO Wen-hai.Research on Ground Motion Characteristics of Large-scale Valley[J].Journal of Disaster Prevention and Mitigation Engineering,2010,30(6):644-649.(in Chinese)
[10]盛志强,卢育霞,石玉成,等.河谷地形的地震反应分析[J].地震工程学报,2013,35(1):126-132.SHENG Zhi-qiang,LU Yu-xia,SHI Yu-cheng,et al.Seismic Response Analysis of Valley Topography[J].China Earthquake Engineering Journal,2013,35(1):126-132.(in Chinese)
[11]徐光兴,姚令侃,李朝红,等.边坡地震动力响应规律及地震动参数影响研究[J].岩土工程学报,2008,30(6):918-923.XU Guang-xing,YAO Ling-kan,LI Zhao-hong,et al.Dynamic Response of Slopes under Earthquakes and Influence of Ground Motion Parameters[J].Chinese Journal of Geotechnical Engineering,2008,30(6):918-923.(in Chinese)
[12]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 of Mechanism of Site Amplification Effects on Ground Motion in Far Field Loess during Wenchuan MS8.0 Earthquake[J].Rock and Soil Mechanics,2012,33(12):3736-3740.(in Chinese)
[13]Louis Geli,Pierre-Yves Bard,Beatrice Jullien.The Effect of Topography on Earthquake Ground Motion:A Review and New Results[J].Bulletin of the Seismological Society of America,1988,78(1):42-63.
[14]王伟.地震动的山体地形效应研究[D].哈尔滨:中国地震局工程力学研究所,2011.WANG Wei.Effect of Hill Topography on the Ground Mote[D].Harbin:Institute of Engineering Mechanics,CEA,2011.(in Chinese)
[15]王海云.土层场地的放大作用随深度的变化规律研究——以金银岛岩土台阵为例[J].地球物理学报,2014,37(3):1498-1509.WANG Hai-yun.Study on Variation of Soil Site Amplification with Depth:A Case at Treasure Island Geotechnical Array,San Franciso Bay[J].Chinese Journal of Geophysics,2014,37(3):1498-1509.(in Chinese)