哈尔滨季节性冻土场地特征参数研究
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摘要
为研究季节性冻土场地冻结期和非冻结期的动力学特征参数及地震动差异,通过哈尔滨场地地脉动单点三分量观测,对比分析不同季节的地脉动特征,采用地脉动单点H/V谱比法研究冻结土层对场地卓越频率、放大因子、等效剪切波速以及场地类别的影响,提出一种冻土层厚度的估算方法。结果表明:冻结土层使地脉动水平分量卓越频率增大,对竖向分量卓越频率的影响不明显;冻结期场地卓越频率增大的幅度除了与覆盖层厚度呈负相关外,还与场地表层刚度有关;冻结土层使场地放大因子减小,减小幅度与覆盖层厚度不相关,与场地表层刚度有关;通过场地剪切波速资料、地脉动H/V谱比卓越频率变化值,便可估算出冻土层厚度;冻结土层使观测场地的等效剪切波速vs_(20)平均增加13%,vs_(30)平均增加11%;vs_(20)的增加未引起Ⅱ类场地类别发生变化,使vs_(20)接近250m/s的Ⅲ类场地变成Ⅱ类场地;vs_(30)的增加没有引起D类场地类别发生变化。
To study the difference of site dynamic parameters and seismic response between unfrozen and frozen seasons,the characteristics of microtremors in frozen and unfrozen seasons were analyzed by 3-component observation in Harbin sites. The effect of frozen soil on site predominant frequency,site amplification factor,equivalent shear wave velocity and site classification were studied by microtremors H/V method. A method for estimating the thickness of the frozen soil was proposed. The results show that the frequency of the horizontal component of microtremors increases because of the frozen soil but the increase of the vertical component is not obvious,and that the increases of the predominant frequency are different among sites even if in the same area.The increase of the site predominant frequency is correlated with both the thickness of the frozen soil and the stiffness of site surface soil. The amplification factor of the site decreases due to the frozen soil,and the decease of the amplification factor is correlated to the stiffness of site surface soil rather than the thickness of the frozen soil.The thickness of the frozen soil can be estimated according to the shear wave velocity of the site and the predominant frequency of the H/V spectra ratio. Due to the frozen soil,the equivalent shear wave velocities,vs_(20) and vs_(30),increase by 13% and 11% on average in six sites respectively. The increase of vs_(20) does not affect the site classification of class Ⅱ,but can change the site of class Ⅲ into class Ⅱ with vs_(20) of nearly 250 m/s. The increase of vs_(30) during the frozen season does not affect the site classification of class D.
To study the difference of site dynamic parameters and seismic response between unfrozen and frozen seasons,the characteristics of microtremors in frozen and unfrozen seasons were analyzed by 3-component observation in Harbin sites. The effect of frozen soil on site predominant frequency,site amplification factor,equivalent shear wave velocity and site classification were studied by microtremors H/V method. A method for estimating the thickness of the frozen soil was proposed. The results show that the frequency of the horizontal component of microtremors increases because of the frozen soil but the increase of the vertical component is not obvious,and that the increases of the predominant frequency are different among sites even if in the same area.The increase of the site predominant frequency is correlated with both the thickness of the frozen soil and the stiffness of site surface soil. The amplification factor of the site decreases due to the frozen soil,and the decease of the amplification factor is correlated to the stiffness of site surface soil rather than the thickness of the frozen soil.The thickness of the frozen soil can be estimated according to the shear wave velocity of the site and the predominant frequency of the H/V spectra ratio. Due to the frozen soil,the equivalent shear wave velocities,vs_(20) and vs_(30),increase by 13% and 11% on average in six sites respectively. The increase of vs_(20) does not affect the site classification of class Ⅱ,but can change the site of class Ⅲ into class Ⅱ with vs_(20) of nearly 250 m/s. The increase of vs_(30) during the frozen season does not affect the site classification of class D.
引文
[1]陈卓识,孟上九,袁晓铭.中等强度地震下季冻区场地响应影响研究[J].土木工程学报,2013,46(增1):166-171.(CHEN Zhuoshi,MENG Shangjiu,YUAN Xiaoming.The impact of parameters inseasonal frozen area response under moderate intensity earthquake[J].China Civil Engineering Journal,2013,46(Supp.1):166-171.(in Chinese))
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[6]COX B R,WOOD C M,HAZIRBABA K.Frozen and unfrozen shear wave velocity seismic site classification of Fairbanks,Alaska[J].Journal of Cold Regions Engineering,2015,26(3):118-145.
[7]齐吉琳,李海鹏,赖远明,等.季节冻土场地上的地脉动特征[J].冰川冻土,2004,26(4):449-453.(QI Jilin,LI Haipeng,LAI Yuanming,et al.Characteristics of microtremor in seasonally frozen ground[J],Journal of Glaciology and Geocryology,2004,26(4):449-453.(in Chinese))
[8]JUNG H O,KIM H J,JO B G,et al.The microtremor HVSRs in the SW Korean Peninsula I:characteristics of the HVSR peak frequency and amplification[J].Science,2010,327(327):94-97.
[9]刘宇实,师黎静.基于地脉动谱比法的场地特征参数快速测定[J].振动与冲击,2018,37(13):235-242.(LIU Yushi,SHI Lijing.Site characteristic parameters quick measurement based on micro-tremor?s H/V spectra[J].Journal of Vibration and shock,2018,37(13):235-242.(in Chinese))
[10]NAKAMURA Y.A modified estimation method for amplification factor of ground and structures using the H/V spectral ratio[J/OL].http://www.sdr.co.jp,2012-03-01.
[11]中华人民共和国国家标准编写组.GB50011-2010建筑抗震设计规范[S].北京:中国建筑工业出版社,2010.(The National Standards Compilation Group of the People?s Republic of China.GB50011-2010 Code for seismic design of building[S].Beijing:China Architecture and Building Press,2010.(in Chinese))
[12]Building Seismic Safety Council(BSSC).NEHRP recommended provisions for seismic regulations for new buildings and other structures[S].Washington,D C:Federal Emergency Management Agency,2003.
[2]王大雁,朱元林,马巍,等.冻土超声波波速与冻土物理力学性质试验研究[J].岩石力学与工程学报,2003,22(11):1 837-1 840.(WANG Dayan,ZHU Yuanlin,MA Wei,et al.Testing study on relationship between ultrasonic wave velocities and physicomechanical property of frozen soils[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(11):1 837-1 840.(in Chinese))
[3]LEBLANC A M,FORTIER R,ALLARD M,et al.Seismic cone penetration test and seismic tomography in permafrost[J].Revue Canadienne De Géotechnique,2004,41(5):796-813.
[4]QI J,MA W,SUN C,et al.Ground motion analysis in seasonally frozen regions[J].Cold Regions Science and Technology,2006,44(2):111-120.
[5]高峰,陈兴冲,严松宏.季节性冻土和多年冻土对场地地震反应的影响[J].岩石力学与工程学报,2006,25(8):1 639-1 644.(GAOFeng,CHEN Xingchong,YAN Songhong.Influence of permafrost and seasonally frozen soil in seismic responses of sites[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(8):1 639-1 644.(in Chinese))
[6]COX B R,WOOD C M,HAZIRBABA K.Frozen and unfrozen shear wave velocity seismic site classification of Fairbanks,Alaska[J].Journal of Cold Regions Engineering,2015,26(3):118-145.
[7]齐吉琳,李海鹏,赖远明,等.季节冻土场地上的地脉动特征[J].冰川冻土,2004,26(4):449-453.(QI Jilin,LI Haipeng,LAI Yuanming,et al.Characteristics of microtremor in seasonally frozen ground[J],Journal of Glaciology and Geocryology,2004,26(4):449-453.(in Chinese))
[8]JUNG H O,KIM H J,JO B G,et al.The microtremor HVSRs in the SW Korean Peninsula I:characteristics of the HVSR peak frequency and amplification[J].Science,2010,327(327):94-97.
[9]刘宇实,师黎静.基于地脉动谱比法的场地特征参数快速测定[J].振动与冲击,2018,37(13):235-242.(LIU Yushi,SHI Lijing.Site characteristic parameters quick measurement based on micro-tremor?s H/V spectra[J].Journal of Vibration and shock,2018,37(13):235-242.(in Chinese))
[10]NAKAMURA Y.A modified estimation method for amplification factor of ground and structures using the H/V spectral ratio[J/OL].http://www.sdr.co.jp,2012-03-01.
[11]中华人民共和国国家标准编写组.GB50011-2010建筑抗震设计规范[S].北京:中国建筑工业出版社,2010.(The National Standards Compilation Group of the People?s Republic of China.GB50011-2010 Code for seismic design of building[S].Beijing:China Architecture and Building Press,2010.(in Chinese))
[12]Building Seismic Safety Council(BSSC).NEHRP recommended provisions for seismic regulations for new buildings and other structures[S].Washington,D C:Federal Emergency Management Agency,2003.
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