地震动参数对斜坡加速度动力响应规律的影响
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摘要
2008年‘5.12’汶川大地震诱发斜坡地质灾害在空间分布上表现出了明显的高程效应和岩性效应。本文采用上硬下软和上软下硬两种典型岩性组合斜坡模型,完成了1:100比尺的振动台试验。文中重点分析了地震波类型(频谱)、激振方向和地震动三参数对斜坡模型水平向加速度动力响应规律的影响。分析结果表明:(1)水平单向激振时,15Hz正弦波和汶川地震波作用下的高程放大效应主要体现在斜坡模型中上段,两者在上软下硬组合斜坡模型中产生了近乎相同的水平向加速度动力响应规律,原因主要在于两者的卓越频率接近。(2)模型对合成向汶川地震波的放大作用依次超过单向水平向和竖直向汶川波的作用,且合成向与水平单向汶川地震波的作用规律基本相同。(3)随着振动强度增加,模型对低频波的放大作用增强。(4)在合成向汶川地震动作用下,随着振动强度增加,模型各高程处的水平向加速度峰值(PGA)逐渐增加,其相应的放大系数在模型中上段逐渐降低至2.0以下,最终趋于平缓,表明模型沿高程向的放大效应逐渐减弱。此外,各参数对模型的水平向加速度响应因模型自身的岩性组合结构而异,随着振动强度增加,上硬下软斜坡模型中上部的水平向速度响应值基本保持在1.0～2.7倍于上软下硬斜坡模型中上部的水平向加速度响应值这一水平。
Evident topographic effect and lithological effect were observed in spatial distribution of secondary geo-hazards caused by 'May 12' Wenchuan earthquake in 2008.Two model slopes composed of different lithology combinations with high strength materials overlying low strength materials and low strength materials overlying high strength materials,are designed to conduct a shaking table test with the geometric scale of 1:100.The effect of seismic parameters on horizontal acceleration responses of two model slopes has been analyzed in detail.Results show that:(1) when in horizontal input motion only,the topographic amplification effects under sine waves of 15 Hz vibration frequency and real waves only occur in the middle to the top part of models.Moreover,the response rules resemble each other in the model with low strength materials overlying high strength materials due to the similar dominant frequencies.(2) Under real waves,the effects under complex direction excitation are basically stronger than those in horizontal motion only and vertical motion only in sequence,and response rules under the first two conditions are similar in curve shape.(3) as input intensity increases,the amplification effects are strengthened in the lower frequencies.(4) under the complex direction excitation of real waves,the peak horizontal accelerations at each elevation demonstrate increase tendency,while their corresponding amplification factors decrease gradually in the upper part of models until the values keep stable bellow 2.0,indicating the decay of the topographic effect.In addition,effects of seismic parameters on horizontal acceleration responses of model slopes vary with the lithology combination,and as input intensity increases,the effects on the model with high strength materials overlying low strength materials are 1.0～2.7 times stronger than those on the model with low strength materials overlying high strength materials in the middle to the top part.
Evident topographic effect and lithological effect were observed in spatial distribution of secondary geo-hazards caused by 'May 12' Wenchuan earthquake in 2008.Two model slopes composed of different lithology combinations with high strength materials overlying low strength materials and low strength materials overlying high strength materials,are designed to conduct a shaking table test with the geometric scale of 1:100.The effect of seismic parameters on horizontal acceleration responses of two model slopes has been analyzed in detail.Results show that:(1) when in horizontal input motion only,the topographic amplification effects under sine waves of 15 Hz vibration frequency and real waves only occur in the middle to the top part of models.Moreover,the response rules resemble each other in the model with low strength materials overlying high strength materials due to the similar dominant frequencies.(2) Under real waves,the effects under complex direction excitation are basically stronger than those in horizontal motion only and vertical motion only in sequence,and response rules under the first two conditions are similar in curve shape.(3) as input intensity increases,the amplification effects are strengthened in the lower frequencies.(4) under the complex direction excitation of real waves,the peak horizontal accelerations at each elevation demonstrate increase tendency,while their corresponding amplification factors decrease gradually in the upper part of models until the values keep stable bellow 2.0,indicating the decay of the topographic effect.In addition,effects of seismic parameters on horizontal acceleration responses of model slopes vary with the lithology combination,and as input intensity increases,the effects on the model with high strength materials overlying low strength materials are 1.0～2.7 times stronger than those on the model with low strength materials overlying high strength materials in the middle to the top part.
引文
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[12]许强,刘汉香,邹威,等.斜坡加速度动力响应特性的大型振动台试验研究[J].岩石力学与工程学报,2010,29(12)2420-2429.XU Qiang,LIU Hanxiang,ZOU Wei,et al.Study on slope dynamic responses of accelerations by large-scale shaking table test[J].ChineseJournal of Rock Mechanics and Engineering,2010,29(12):2420-2429.(in Chinese)
[13]刘汉香,许强,徐鸿彪,等.斜坡动力变形破坏特征的振动台模型试验研究[J].岩土力学,32(增2):334-339.LIU Hanxiang,XU Qiang,XU Hongbiao,et al.Shaking table model test on slope dynamic deformation and failure[J].Soil and Rock Mechan-ics,32(supplement 2):334-339.(in Chinese)
[14]邹威,许强,刘汉香,等.强震作用下层状岩质斜坡破坏的大型振动台试验研究[J].地震工程与工程振动,2011,31(3):143-149.ZOU Wei,XU Qiang,LIU Hanxiang,et al.Large-scale shaking table model test study on failure of layered rocky slope under strong ground mo-tion[J].Journal of Earthquake and Engineering Vibration,2011,31(3):143-149.(in Chinese)
[2]刘红帅,薄景山,刘德东.岩土边坡地震稳定性评价方法研究进展[J].防灾科技学院学报,2007,9(3):20-27.LIU Hongshuai,BO Jingshan,LIU Dedong.Development on study of seismic stability evaluation methods of rock-soil slopes[J].Journal of Insti-tute of Disaster-Prevention Science and Technology,2007,9(3):20-27.(in Chinese)
[3]Strasser F O,Bommer J J.Large-amplitude ground-motion recordings and their interpretations[J].Soil Dynamics and Earthquake Engineering,2009,29:1305-1329.
[4]Yang J,Yan X R.Factors affecting site response to multi-directional earthquake loading[J].Engineering Geology,2009,107:77-87.
[5]Shoji Y,Tanii K,Kamiyama M..A study on the duration and amplitude characteristics of earthquake ground motions[J].Soil Dynamics andEarthquake Engineering,2005,25:505-512.
[6]梁庆国,韩文峰,马润勇,等.强地震动作用下层状岩体破坏的物理模拟研究[J].岩土力学,2005,26(8):1307-1311.LIANG Qingguo,HAN Wenfeng,MA Runyong,et al.Physical simulation study on dynamic failures of layered rock masses under strong groundmotion[J].Rock and Soil Mechanics,2005,26(8):1307-1311.(in Chinese)
[7]祁生文,伍法权.边坡动力响应规律研究[J].中国科学E辑技术科学,2003,33(增刊):28-40.QI Shengwen,WU Faquan.Study on dynamic responses of slope[J].Science in China Ser.E Technological Sciences,2003,33(Supplyment):28-40.(in Chinese)
[8]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):0918-0923.XU Guangxing,YAO Lingkan,LI Zhaohong,et al.Dynamic response of slopes under earthquakes and influence of ground motion parameters[J].Chinese Journal of Geotechnical Engineering,2008,30(6):0918-0923.(in Chinese)
[9]许强,黄润秋.5.12汶川大地震诱发大型崩滑灾害动力特征初探[J].工程地质学报,2008,16(6):721-729.XU Qiang,HUANG Runqiu.Kinetics charateristics of large landslides triggered by May 12th Wenchuan earthquake[J].Journal of EngineeringGeology,2008,16(6):721-729.(in Chinese)
[10]Tang H M,Jia H B,Hu X L,et al.Characteristics of landslides induced by the great Wenchuan earthquake[J].Journal of Earth Science,2010,21(1):104–11.
[11]王秀英,聂高众,王登伟.汶川地震诱发滑坡与地震动峰值加速度对应关系研究[J].岩石力学与工程学报,2010,29(1):82-89.WANG Xiuying,NIE Gaozhong,WANG Dengwei.Research on relationship between landslides and peak ground accelerations induced by Wen-chuan earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(1):82-89.(in Chinese)
[12]许强,刘汉香,邹威,等.斜坡加速度动力响应特性的大型振动台试验研究[J].岩石力学与工程学报,2010,29(12)2420-2429.XU Qiang,LIU Hanxiang,ZOU Wei,et al.Study on slope dynamic responses of accelerations by large-scale shaking table test[J].ChineseJournal of Rock Mechanics and Engineering,2010,29(12):2420-2429.(in Chinese)
[13]刘汉香,许强,徐鸿彪,等.斜坡动力变形破坏特征的振动台模型试验研究[J].岩土力学,32(增2):334-339.LIU Hanxiang,XU Qiang,XU Hongbiao,et al.Shaking table model test on slope dynamic deformation and failure[J].Soil and Rock Mechan-ics,32(supplement 2):334-339.(in Chinese)
[14]邹威,许强,刘汉香,等.强震作用下层状岩质斜坡破坏的大型振动台试验研究[J].地震工程与工程振动,2011,31(3):143-149.ZOU Wei,XU Qiang,LIU Hanxiang,et al.Large-scale shaking table model test study on failure of layered rocky slope under strong ground mo-tion[J].Journal of Earthquake and Engineering Vibration,2011,31(3):143-149.(in Chinese)
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