地震作用下各向异性地基的动力响应——离心机模型试验研究
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摘要
砂土颗粒之间接触的法向分布和颗粒形状所引起的内在各向异性会对地基的地震响应有明显的影响。为了深入认识砂土内在各向异性对地层动力响应的影响,制作了专门的离心机模型箱以控制砂土的不同沉积方向模拟砂土的内在各向异性,并且通过一系列离心机振动模型试验再现了砂土内在各向异性对砂土动力学特性的影响,包括对地层加速度、位移和超孔隙水压力的影响。研究发现,尤其在饱和情况下,砂土的内在各向异性对砂土的动力学特性影响非常大,沉积方向为90度的砂样模型抗液化能力明显较差,导致较大的沉降。为了更加准确的预测结构物在地震区的动力特性,建议在工程设计中应考虑砂土内在各向异性的影响。
Intrinsic anisotropy caused by the contact normal distribution and particle shape may have obvious effect on the seismic response of the foundation.To examine the effect of intrinsic anisotropy on seismic response of earth layer,a special rigid container was made to control different directions of soil deposition,simulate the anisotropy of the sand and reproduce the effect of the intrinsic anisotropy on dynamic behavior of the sand,including acceleration,velocity,displacement and super pore water pressure through a series of model tests.Test results show that the effect is obvious especially in the saturated condition,while the liquefaction resistance capability of the sand sample modeled with 90° deposition direction is less obvious,which would lead to large settlement.To better predict the dynamic behavior of structures in seismic area,it is suggested to consider the effect of the intrinsic anisotropy of the sand in engineering.
Intrinsic anisotropy caused by the contact normal distribution and particle shape may have obvious effect on the seismic response of the foundation.To examine the effect of intrinsic anisotropy on seismic response of earth layer,a special rigid container was made to control different directions of soil deposition,simulate the anisotropy of the sand and reproduce the effect of the intrinsic anisotropy on dynamic behavior of the sand,including acceleration,velocity,displacement and super pore water pressure through a series of model tests.Test results show that the effect is obvious especially in the saturated condition,while the liquefaction resistance capability of the sand sample modeled with 90° deposition direction is less obvious,which would lead to large settlement.To better predict the dynamic behavior of structures in seismic area,it is suggested to consider the effect of the intrinsic anisotropy of the sand in engineering.
引文
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[2]Guo P J.Modified direct shear test for anisotropic strength of sand[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2008,134(9):1311-1318.
[3]张坤勇,殷宗泽,梅国雄.土体两种各向异性的区别和联系[J].岩石力学与工程学报,2004,25(9):1503-1509.ZHANG Kunyong,YIN Zongze,MEI Guoxiong.Difference and connection of two kinds of anisotropy of soils[J].Chinese Journal of RockMechanics And Engineering,2005,24(9):1503-1509.(in Chinese)
[4]Simpson B,Tatsuoka K.Geotechnics:the next 60 years[J].Geotechnique,2008,58(5):357-368.
[5]宋飞,张建民,刘超.各向异性砂土K0试验研究[J].岩土力学,2010,31(12):3727-3735.SONG Fei,ZHANG Jianmin,LIU Chao.Experimental study of K0 of anisotropic sand[J].Rock and Soil Mechanics,2010,31(12):3727-3735.(in Chinese)
[6]宋飞,张建民.考虑侧向变形的各向异性砂土土压力试验研究[J].岩石力学与工程学报,2009,28(9):1884-1895.SONG Fei,ZHANG Jianmin.Experimental study of earth pressure for anisotropic sand considering lateral displacement[J].Chinese Journal ofRock Mechanics And Engineering,2009,28(9):1884-1895.(in Chinese)
[7]谢国忠,周先雁,温佩琳.各向异性场地动力特性地微动研究[J].自然灾害学报,2009,18(3):19-24.XIE Guozhong,ZHOU Xianyan,WEN Peilin.Research on dynamic properties of inhomogeneous anisotropic site by ground microtremor[J].Journal of Natural Disasters,2009,18(3):19-24.(in Chinese)
[8]冯志仁,郭德存,刘红帅,等.最大剪切模量对土动力参数及地震反应的影响[J].自然灾害学报,2007,16(3):90-95.FENG Zhiren,GUO Decun,LIU Hongshuai,et al.Influence of maximum shear modulus on dynamic parameter and seismic response of soil layer[J].Journal of Natural Disasters,2007,16(3):90-95.(in Chinese)
[9]孙锐,袁晓铭,王永志,等.NEES系统中振动离心机最新进展及国内振动离心机发展设想[J].世界地震工程,2010,86(1):31-39.SUN Rui,YUAN Xiaoming,WANG Yongzhi,et al.Latest progress of centrifugal shakers in NEES and developmental conception of domesticcentrifugal sheakers[J].World Earthquake Engineering,2010,86(1):31-39.(in Chinese)
[10]王永志,袁晓铭,孙锐.大型振动离心机设备关键技术研究[J].世界地震工程,2011,27(2):113-123.WANG Yongzhi,YUAN Xiaoming,SUN Rui.Critical technique of design for Large Scale Centrifugal Shakers[J].World EarthquakeEngineering,2011,27(2):31-39.(in Chinese)
[11]Li B,Zeng X,Min H.Seismic responses of a retaining wall with anisotropic backfill[C]∥Earth Retention Conference 3,2010,GSP.208:688-695.
[12]Li B,Zeng X,Effect of fabric anisotropy on seismic response of strip foundations[C]∥Georisk-Geotechnical Risk Assessment and Manage-ment,2011,GSP.224:326-335.
[13]Kawai T,Kanatani M.Seismic performance of a caisson type seawall with an armored embankment[C]∥Proceedings,Centrifuge 98,1998:351-358.
[14]Behringer R P,Daniels K E,Majmudar T S,et al.Fluctuations,correlations and transitions in granular materials:statistical mechanics for a non-conventional system[J].Phil.Trans.R.Soc.A,2008,366:493-504.
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