液化判别应力折减系数分布特征研究
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摘要
基于FLAC3D软件对饱和砂土离心机振动台模型试验进行数值标定,以获取合理的分析模型,然后采用数值模拟分析不同地震波和简谐波下模型地基内部应力折减系数rd的分布规律。研究表明,已有经验公式能较好地描述土体未液化时应力折减系数的分布形式,但土体液化后土层剪应力分布与经验公式预测值存在显著差别。地震动作用的作用时间对折减系数也有较大影响,其中,孔隙水压力增长水平和土体软化程度是重要影响因素。而地震动频率对rd的影响则主要与场地卓越频率相关,地震动频率越接近场地卓越频率,rd沿土层深度的变化越剧烈。因此,液化评价中采用Seed-Idriss简化公式估算CSR时,需要综合考虑地震动特征和场地条件对rd分布的影响。
To investigate the distribution features of rd under different types of excitations,firstly FLAC 3D is used to calibrate the results of dynamic centrifuge tests on saturated sand;and then the validated numerical model is used to study the variation of rd curves with soil depth under seismic and harmonic excitations.The results show that the proposed empirical equation of rd is fairly accurate in non-liquefied cases;whereas larger differences exist between the distribution of shear stresses and the predicted values by empirical equation in liquefied cases.Besides,the duration of seismic excitation also influences rd,where the generation level of pore water pressure and the softening degree of soil are major factors.As for the effect of seismic input frequency,it is closely related to the predominant frequency of the site;i.e.the closer the two frequencies become,the more drastic the variation of rd curve is.Therefore,the effects of seismic motion and site conditions should be considered when the Seed-Idriss equation is used to calculate CSR in liquefaction evaluation.
To investigate the distribution features of rd under different types of excitations,firstly FLAC 3D is used to calibrate the results of dynamic centrifuge tests on saturated sand;and then the validated numerical model is used to study the variation of rd curves with soil depth under seismic and harmonic excitations.The results show that the proposed empirical equation of rd is fairly accurate in non-liquefied cases;whereas larger differences exist between the distribution of shear stresses and the predicted values by empirical equation in liquefied cases.Besides,the duration of seismic excitation also influences rd,where the generation level of pore water pressure and the softening degree of soil are major factors.As for the effect of seismic input frequency,it is closely related to the predominant frequency of the site;i.e.the closer the two frequencies become,the more drastic the variation of rd curve is.Therefore,the effects of seismic motion and site conditions should be considered when the Seed-Idriss equation is used to calculate CSR in liquefaction evaluation.
引文
[1]鲁晓兵,谈庆明,王淑云,等.饱和砂土液化研究新进展[J].力学进展,2004,34(1):87-96.(LU Xiaobing,TAN Qingming,WANG Shuyun,et al.The advances of liquefaction research on saturated soils[J].Advances in Mechanics,2004,34(1):87-96.(in Chinese))
[2]王刚,张建民.地震液化问题研究进展[J].力学进展,2007,37(4):575-589.(WANG Gang,ZHANG Jianmin.Recent advances in seismic liquefaction research[J].Advances in Mechanics,2007,37(4):575-589.(in Chinese))
[3]孙锐,袁晓铭.第11届国际土动力学和地震工程会议及第13届世界地震工程会议砂土液化研究综述[J].世界地震工程,2006,22(1):15-20.(SUN Rui,YUAN Xiaoming.Summarization of earthquake liquefaction on13th WCEE and11th SDEE[J].World Earthquake Engineering,2006,22(1):15-20.(in Chinese))
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[5]蔡国军,刘松玉,童立元,等.基于静力触探测试的国内外砂土液化判别方法[J].岩石力学与工程学报,2008,27(5):1020-1027.(CAI Guojun,LIU Songyu,TONG Liyuan,et al.Evaluation of liquefaction of sandy soils based on cone penetration test[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(5):1020-1027.(in Chinese))
[6]周燕国,陈云敏,柯瀚.砂土液化势剪切波速简化判别法的改进[J].岩石力学与工程学报,2005,24(13):2369-2375.(ZHOU Yanguo,CHEN Yunmin,KE Han.Improvement of simplified procedure for liquefaction potential evaluation of sands by shear wave velocity[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(13):2369-2375.(in Chinese))
[7]ZHOU Y G,CHEN Y M.Laboratory investigation on assessing liquefaction resistance of sandy soils by shear wave velocity[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2007,133(8):959-972.
[8]SEED H B,IDRISS I M.Simplified procedure for evaluating soil liquefaction potential[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1971,97(9):1249-1273.
[9]ISHIHARA K.Simple method of analysis for liquefaction of sand deposits during earthquakes[J].Soils and Foundations,1977,17(3):1-17.
[10]IMAI T,TONOUCHI K,KANEMORI T.The simple evaluation method of shear stress generated by earthquakes in soil ground[R].[S.l.]:Bureau of Practical Geological Investigation,1981.
[11]IWASAKI T.Soil liquefaction studies in Japan:state-of-the-art[J].Soil Dynamics and Earthquake Engineering,1986,5(1):2-68.
[12]LIAO S S C,WHITMAN R V.Overburden correction factors for SPT in sands[J].Journal of the Geotechnical Engineering Divisions,ASCE,1986,112(3):373-377.
[13]CETIN K O,SEED R B.Nonlinear shear mass participation factor(d r)for cyclic shear stress ratio evaluation[J].Soil Dynamics and Earthquake Engineering,2004,24(2):103-113.
[14]林华国,贾兆宏,张立丽.砂土液化判别方法研究[J].岩土工程技术,2007,21(2):89-93.(LIN Huaguo,JIA Zhaohong,ZHANG Lili.Study on the method of sand liquefaction evaluation[J].Geotechnical Engineering Technique,2007,21(2):89-93.(in Chinese))
[15]姜涛.尾矿坝砂土液化的简化判别方法[C]//构筑物抗震.北京:测绘出版社,1990.(JIANG Tao.Simplified method to evaluate the liquefaction potential of soil and sand[C]//Antiseism of Structures.Beijing:Surveying and Mapping Press,1990.(in Chinese))
[16]高艳平,王余庆,辛鸿博.尾矿坝地震液化简化判别法[J].岩土工程学报,1995,17(5):72-79.(GAO Yanping,WANG Yuqing,XIN Hongbo.A simplified procedure for evaluating liquefaction potential of tailings dam[J].Chinese Journal of Geotechnical Engineering,1995,17(5):72-79.(in Chinese))
[17]张超,杨春和.尾矿坝液化判别简化方法研究[J].岩石力学与工程学报,2006,25(增2):3730-3736.(ZHANG Chao,YANG Chunhe.Study on a simplified procedure for evaluating liquefaction potential of tailings dam[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(Supp.2):3730-3736.(in Chinese))
[18]ZHOU Y G,CHEN Y M,SHAMOTO Y.Verification of the soil-type specific correlation between liquefaction resistance and shear-wave velocity of sand by dynamic centrifuge test[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2010,136(1):165-177.
[19]Itasca Consulting Group Inc.FLAC3D user′s guide[M].Minneapolis,MN:Itasca,2006.
[20]陈育民.砂土液化后流动大变形试验与计算方法研究[博士学位论文][D].南京:河海大学,2007.(CHEN Yumin.Laboratory study and calculating method of large spreading deformation induced by post-liquefied sand[Ph.D.Thesis][D].Nanjing:Hohai University,2007.(in Chinese))
[21]BYRNE P M,PARK S S,BEATY M,et al.Numerical modeling of liquefaction and comparison with centrifuge tests[J].Canadian Geotechnical Journal,2004,41(2):193-211.
[22]孙锐,袁晓铭.液化土层地震动特征分析[J].岩土工程学报,2004,26(5):684-690.(SUN Rui,YUAN Xiaoming.Analysis of feature of surface ground motion for liquefied soil layer[J].Chinese Journal of Geotechnical Engineering,2004,26(5):684-690.(in Chinese))
[2]王刚,张建民.地震液化问题研究进展[J].力学进展,2007,37(4):575-589.(WANG Gang,ZHANG Jianmin.Recent advances in seismic liquefaction research[J].Advances in Mechanics,2007,37(4):575-589.(in Chinese))
[3]孙锐,袁晓铭.第11届国际土动力学和地震工程会议及第13届世界地震工程会议砂土液化研究综述[J].世界地震工程,2006,22(1):15-20.(SUN Rui,YUAN Xiaoming.Summarization of earthquake liquefaction on13th WCEE and11th SDEE[J].World Earthquake Engineering,2006,22(1):15-20.(in Chinese))
[4]陈国兴,胡庆兴,刘雪珠.关于砂土液化判别的若干意见[J].地震工程与工程振动,2002,22(1):141-151.(CHEN Guoxing,HU Qingxing,LIU Xuezhu.Some comments on methodologies for estimating liquefaction of sandy soils[J].Earthquake Engineering and Engineering Vibration,2002,22(1):141-151.(in Chinese))
[5]蔡国军,刘松玉,童立元,等.基于静力触探测试的国内外砂土液化判别方法[J].岩石力学与工程学报,2008,27(5):1020-1027.(CAI Guojun,LIU Songyu,TONG Liyuan,et al.Evaluation of liquefaction of sandy soils based on cone penetration test[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(5):1020-1027.(in Chinese))
[6]周燕国,陈云敏,柯瀚.砂土液化势剪切波速简化判别法的改进[J].岩石力学与工程学报,2005,24(13):2369-2375.(ZHOU Yanguo,CHEN Yunmin,KE Han.Improvement of simplified procedure for liquefaction potential evaluation of sands by shear wave velocity[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(13):2369-2375.(in Chinese))
[7]ZHOU Y G,CHEN Y M.Laboratory investigation on assessing liquefaction resistance of sandy soils by shear wave velocity[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2007,133(8):959-972.
[8]SEED H B,IDRISS I M.Simplified procedure for evaluating soil liquefaction potential[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1971,97(9):1249-1273.
[9]ISHIHARA K.Simple method of analysis for liquefaction of sand deposits during earthquakes[J].Soils and Foundations,1977,17(3):1-17.
[10]IMAI T,TONOUCHI K,KANEMORI T.The simple evaluation method of shear stress generated by earthquakes in soil ground[R].[S.l.]:Bureau of Practical Geological Investigation,1981.
[11]IWASAKI T.Soil liquefaction studies in Japan:state-of-the-art[J].Soil Dynamics and Earthquake Engineering,1986,5(1):2-68.
[12]LIAO S S C,WHITMAN R V.Overburden correction factors for SPT in sands[J].Journal of the Geotechnical Engineering Divisions,ASCE,1986,112(3):373-377.
[13]CETIN K O,SEED R B.Nonlinear shear mass participation factor(d r)for cyclic shear stress ratio evaluation[J].Soil Dynamics and Earthquake Engineering,2004,24(2):103-113.
[14]林华国,贾兆宏,张立丽.砂土液化判别方法研究[J].岩土工程技术,2007,21(2):89-93.(LIN Huaguo,JIA Zhaohong,ZHANG Lili.Study on the method of sand liquefaction evaluation[J].Geotechnical Engineering Technique,2007,21(2):89-93.(in Chinese))
[15]姜涛.尾矿坝砂土液化的简化判别方法[C]//构筑物抗震.北京:测绘出版社,1990.(JIANG Tao.Simplified method to evaluate the liquefaction potential of soil and sand[C]//Antiseism of Structures.Beijing:Surveying and Mapping Press,1990.(in Chinese))
[16]高艳平,王余庆,辛鸿博.尾矿坝地震液化简化判别法[J].岩土工程学报,1995,17(5):72-79.(GAO Yanping,WANG Yuqing,XIN Hongbo.A simplified procedure for evaluating liquefaction potential of tailings dam[J].Chinese Journal of Geotechnical Engineering,1995,17(5):72-79.(in Chinese))
[17]张超,杨春和.尾矿坝液化判别简化方法研究[J].岩石力学与工程学报,2006,25(增2):3730-3736.(ZHANG Chao,YANG Chunhe.Study on a simplified procedure for evaluating liquefaction potential of tailings dam[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(Supp.2):3730-3736.(in Chinese))
[18]ZHOU Y G,CHEN Y M,SHAMOTO Y.Verification of the soil-type specific correlation between liquefaction resistance and shear-wave velocity of sand by dynamic centrifuge test[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2010,136(1):165-177.
[19]Itasca Consulting Group Inc.FLAC3D user′s guide[M].Minneapolis,MN:Itasca,2006.
[20]陈育民.砂土液化后流动大变形试验与计算方法研究[博士学位论文][D].南京:河海大学,2007.(CHEN Yumin.Laboratory study and calculating method of large spreading deformation induced by post-liquefied sand[Ph.D.Thesis][D].Nanjing:Hohai University,2007.(in Chinese))
[21]BYRNE P M,PARK S S,BEATY M,et al.Numerical modeling of liquefaction and comparison with centrifuge tests[J].Canadian Geotechnical Journal,2004,41(2):193-211.
[22]孙锐,袁晓铭.液化土层地震动特征分析[J].岩土工程学报,2004,26(5):684-690.(SUN Rui,YUAN Xiaoming.Analysis of feature of surface ground motion for liquefied soil layer[J].Chinese Journal of Geotechnical Engineering,2004,26(5):684-690.(in Chinese))
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