地震动输入界面的选取对地震动参数的影响
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摘要
地震反应分析中的输入界面是一种规定的假想基岩面,其选取具有很大的不确定性,对确定地震动参数的影响很大。本文以北京地区存在剪切波速较高的卵石硬夹层场地为研究对象,探讨实际工程场地中能否将硬夹层选作地震动输入界面的问题。利用一维等效线性化波动方法,对390个含有剪切波速高于500m/s的卵石层场地模型进行地震反应分析计算,讨论卵石层的上覆土层、下伏土层以及卵石层自身特性对地震反应分析结果的影响。计算结果显示,厚度5m左右、剪切波速小于600m/s的卵石层作为地震动输入界面是否合理,主要取决于上覆土层和下伏土层,而卵石层厚度和剪切波速的影响很小。对于一般性工程,当上覆土层厚度大于15m,下伏土层厚度在10m以内时,选取硬夹层顶面与选取钻探揭示的基岩或剪切波速不小于500m/s的土体顶面为输入界面,计算结果差别不大;当上覆土层厚度达到60m,下伏土层的变化对计算结果影响很小。研究表明,在钻探没有揭示出基岩或坚硬土体时,埋深大于60m的硬夹层可以选为地震动输入界面,这一结论对实际的地震安全性评价工作具有一定参考价值。
Inputting interface in seismic-response calculation is a required imaginary bedrock surface.The choice of different seismic inputting interfaces has a great influence on the ground motion parameters.In this paper,we will use the cobble layer with high shear wave velocity in the Beijing area to discuss whether the hard layer can be used as inputting interface in practical engineering,1-D equivalent linear wave methodology is adopted for the seismic-response calculation on 390 engineering site soil profiles which includes some cobble layers with shear wave velocity more than 500m/s.The result shows that overlaying soil and underlying ground of cobble layer play an important role in choosing sort of cobble layer with around 5m thick and less than 600m/s as reasonable inputting interface;thickness of cobble layer and wave velocity,on the other hand,play minor roles.For general buildings,when the overlaying soil is more than 15m thick and the underlying ground is less than 10m thick,there is no significant difference in calculation results when choosing hard layers or bedrock as inputting interface.In addition,variation of underlying ground's thickness has less effect on calculation when the thickness of overlaying soil reaches more than 60m.Therefore,hard soil layers buried in 60m or more in depth could be used as the inputting interface in the absence of information about bedrock.
Inputting interface in seismic-response calculation is a required imaginary bedrock surface.The choice of different seismic inputting interfaces has a great influence on the ground motion parameters.In this paper,we will use the cobble layer with high shear wave velocity in the Beijing area to discuss whether the hard layer can be used as inputting interface in practical engineering,1-D equivalent linear wave methodology is adopted for the seismic-response calculation on 390 engineering site soil profiles which includes some cobble layers with shear wave velocity more than 500m/s.The result shows that overlaying soil and underlying ground of cobble layer play an important role in choosing sort of cobble layer with around 5m thick and less than 600m/s as reasonable inputting interface;thickness of cobble layer and wave velocity,on the other hand,play minor roles.For general buildings,when the overlaying soil is more than 15m thick and the underlying ground is less than 10m thick,there is no significant difference in calculation results when choosing hard layers or bedrock as inputting interface.In addition,variation of underlying ground's thickness has less effect on calculation when the thickness of overlaying soil reaches more than 60m.Therefore,hard soil layers buried in 60m or more in depth could be used as the inputting interface in the absence of information about bedrock.
引文
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卢寿德,2006,工程场地地震安全性评价宣贯教材(GB17741-2005),98～100,北京:中国标准出版社。
薄景山、李秀领、刘德东等,2003a,土层结构对反应谱特征周期的影响.地震工程与工程振动,23(5):42～45。
薄景山、李秀领、刘德东等,2003b,土层结构对反应谱平台值的影响.地震工程与工程振动,23(4):29～33。
薄景山、李秀领、李山有,2003c,场地条件对地震动影响研究的若干进展.世界地震工程,19(2):11～15。
吕悦军、彭艳菊、兰景岩等,2008,场地条件对地震动参数影响的关键问题研究.震灾防疫技术,3(2):126～135。
林建生、陈俊峰、林子健等,2006,场地地震安全性评价中确定设计的震动参数方面若干问题的研究.世界地震工程,22(4):150～159。
中华人民共和国国家质量监督检验检疫总局、中国国家标准化管理委员会,2005,GB17741-2005,工程场地地震安全性评价,北京:中国标准出版社。
陈国兴、陈继华,2005,地震动输入界面的选取对深软场地地震效应的影响,世界地震工程,21(2):36～43。
廖振鹏、李小军,1989,地表土层地震反应的等效线性化解法,地震小区化(理论与实践),141～153,北京:地震出版社。
施春花,2009,北京地区场地条件对地震动参数的影响,中国地震局地壳应力研究所硕士论文,24～61。
胡聿贤,2003,地震安全性评价技术教程,355～379,北京:地震出版社。
卢寿德,2006,工程场地地震安全性评价宣贯教材(GB17741-2005),98～100,北京:中国标准出版社。
薄景山、李秀领、刘德东等,2003a,土层结构对反应谱特征周期的影响.地震工程与工程振动,23(5):42～45。
薄景山、李秀领、刘德东等,2003b,土层结构对反应谱平台值的影响.地震工程与工程振动,23(4):29～33。
薄景山、李秀领、李山有,2003c,场地条件对地震动影响研究的若干进展.世界地震工程,19(2):11～15。
吕悦军、彭艳菊、兰景岩等,2008,场地条件对地震动参数影响的关键问题研究.震灾防疫技术,3(2):126～135。
林建生、陈俊峰、林子健等,2006,场地地震安全性评价中确定设计的震动参数方面若干问题的研究.世界地震工程,22(4):150～159。
中华人民共和国国家质量监督检验检疫总局、中国国家标准化管理委员会,2005,GB17741-2005,工程场地地震安全性评价,北京:中国标准出版社。
陈国兴、陈继华,2005,地震动输入界面的选取对深软场地地震效应的影响,世界地震工程,21(2):36～43。
廖振鹏、李小军,1989,地表土层地震反应的等效线性化解法,地震小区化(理论与实践),141～153,北京:地震出版社。
施春花,2009,北京地区场地条件对地震动参数的影响,中国地震局地壳应力研究所硕士论文,24～61。
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