固结压力相关的黏土动力特性模型研究及应用
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摘要
对一种粉质黏土进行了不同固结压力下的循环单剪试验,得到了相应各固结压力下的动剪模量和阻尼比随动剪应变幅值非线性变化的Gd-γd曲线和D-γd曲线,并对其进行了归一化。试验结果表明,即使是归一化以后的动力特性曲线,仍然因固结压力不同而出现差异;固结压力越大,Gd/Gdmax-γd曲线衰减越慢,而D/Dmax-γd曲线增加也越缓。通过建立最大动剪模量、最大阻尼比和参考剪应变与固结压力之间的试验关系式,建议了一种实用的固结压力相关的黏土动力特性模型。最后,通过算例表明,场地土体动力特性随固结压力而变化的特征不但会影响场地地震反应的幅值,而且将影响其频谱特性,且场地覆盖层厚度越大,影响越强烈。
Cyclic simple shear tests are conducted on a silty clay with different axial consolidation pressures;and nonlinear dynamic property curves,Gd vs.γ d curve and D vs.γ d curve,of soil under different test consolidation pressures,where Gd,γ d and D are dynamic shear modulus,dynamic shear strain radio and damping ratio respectively,are obtained.Results indicate that even normalized dynamic property curves of soil under different consolidation pressures exhibit differences.Along with the build up of consolidation pressure,the degradation of Gd/ Gdmax-γ d curve slows down;and the increase of D/ Dmax-γ d curve delays.Based on the experimental relationship between maximum dynamic shear modulus,maximum damping ratio,reference shear strain and the consolidation pressure separately,a novel consolidation pressure correlated dynamic property curve model of clay is proposed.Application of the consolidation pressure correlated model for site response is carried out.Results indicate that the property of soil dynamics varid with the consolidation pressure will affect not only the magnitude but also the frequency spectrum properties of the site response,and the thicker of overlay,the more obvious of the affects.
Cyclic simple shear tests are conducted on a silty clay with different axial consolidation pressures;and nonlinear dynamic property curves,Gd vs.γ d curve and D vs.γ d curve,of soil under different test consolidation pressures,where Gd,γ d and D are dynamic shear modulus,dynamic shear strain radio and damping ratio respectively,are obtained.Results indicate that even normalized dynamic property curves of soil under different consolidation pressures exhibit differences.Along with the build up of consolidation pressure,the degradation of Gd/ Gdmax-γ d curve slows down;and the increase of D/ Dmax-γ d curve delays.Based on the experimental relationship between maximum dynamic shear modulus,maximum damping ratio,reference shear strain and the consolidation pressure separately,a novel consolidation pressure correlated dynamic property curve model of clay is proposed.Application of the consolidation pressure correlated model for site response is carried out.Results indicate that the property of soil dynamics varid with the consolidation pressure will affect not only the magnitude but also the frequency spectrum properties of the site response,and the thicker of overlay,the more obvious of the affects.
引文
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[2]顾尧章.海底黏土的剪切模量[J].岩土工程学报,1995,17(2):30-35.GU Yao-zhang.Shear modulus of the marine clay[J].Chinese Journal of Geotechnical Engineering,1995,17(2):30-35.
[3]陈国兴,谢君斐,张克绪.土的动模量和阻尼比的经验估计[J].地震工程与工程振动,1995,15(1):73-74.CHEN Guo-xing,XIE Jun-fei,ZHANG Ke-xu.The empirical evaluation of soil modulus and damping ratio for dynamic analysis[J].Earthquake Engineering and Engineering Vibration,1995,15(1):73-74.
[4]袁晓铭,孙锐,孙静,等.常规土类动剪切模量比和阻尼比试验研究[J].地震工程与工程振动,2000,20(4):133-139.YUAN Xiao-ming,SUN Rui,SUN Jing,et al.Laboratory experimental study on dynamic shear modulus ratio and damping ratio of soils[J].Earthquake Engineering and Engineering Vibration,2000,20(4):133-139.
[5]尚守平,卢华喜,任惠,等.粉质黏土动剪切模量的试验对比研究[J].岩土工程学报,2006,28(3):410-414.SHANG Shou-ping,LU Hua-xi,REN Hui,et al.Comparative study on dynamic shear modulus of silty clay[J].Chinese Journal of Geotechnical Engineering,2006,28(3):410-414.
[6]王志良.土的非线性动力性质与场地地震反应[M].地基与工业建筑抗震.北京:地震出版社,1983.
[7]DERENDELLI M B.Development of a new family of normalized modulus reduction and material damping curves[PhD Dissertation].Austin,Texas:University of Texas at Austin,2001:362.
[8]CLIFF ROBLEE.BRIAN CHIOU.A Proposed Geoindex Model for Design Selection of Non-linear Properties for Site Response Analyses[C]//Proceedings of the NSF/PEER.UC Berkeley,Workshop on Uncertainties in Nonlinear Soil Properties and their Impact on Modeling Dynamic Soil Response.California:[s.n.],2004.
[9]尚守平,刘方成,杜运兴,等.应变累积对黏土动剪模量和阻尼比影响的试验研究[J].岩土力学,2006,27(5):683-688.SHANG Shou-ping,LIU Fang-cheng,DU Yun-xing,et al.Experimental study on effect of shear strain accumulation on dynamic shear modulus and damping ratio of clay soil[J].Rock and Soil Mechanics,2006,27(5):683-688.
[10]HARDIN B C,DRNEVICH V P.Shear modulus and damping in soil:design and curves[J].Journal of Soil Mechanics and Foundations Division,ASCE,1972,98(7):667-692.
[11]谢定义.土动力学[M].西安:西安交通大学出版社,1988:140-195
[12]尚守平,刘方成,王海东.基于阻尼的地震循环荷载作用下黏土非线性模型[J].土木工程学报,2007,40(3):74-82.SHANG Shou-ping,LIU Fang-cheng,WANG Hai-dong.Nonlinear model based on damping ratio for clays under seismic loading[J].China Civil Engineering Journal,2007,40(3):74-82.
[13]孙静,袁晓铭.固结比对砂土动剪切模量及地表反应谱的影响[J].岩土力学,2007,28(3):443-448.SUN Jing,YUAN Xiao-ming.Effects of consolidation ratios of sands on dynamic shear modulus and response spectrum of soil surface[J].Rock and Soil Mechanics,2007,28(3):443-448.
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