强风化花岗岩动力学参数的试验研究
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摘要
地震反应分析通常采用等效非线性模型,动剪切模量G和阻尼比λ是该模型的两个重要参数。为研究目前在大型工程建设中遇到越来越多的强风化花岗岩的动力特性,利用固定-自由型共振柱(GDS RCA)对强风化花岗岩的剪切模量和阻尼比进行试验研究。GDS RCA为一种国际上广泛应用的共振柱,具有良好的性能,利用其控制试样的固结围压和孔隙水压力,可以测得试样在不同有效应力状况下的动剪切模量和阻尼比。对比研究不同有效应力下共振频率、动剪切模量和阻尼比随剪应变的变化情况,给出其变化曲线。按照Hadin-Drnevich[1]所提出的双曲线模型,拟合动剪切模量比和阻尼比随剪应变的变化曲线。利用摩擦理论,对试样阻尼的产生机制进行探讨。试验结果表明,随着剪应变的增加,试样系统的共振频率随之减小,试样阻尼比随之增大;试样的动剪切模量和阻尼比皆与试样固结时的有效应力有关,而试样阻尼比也受孔隙水压力的影响。
Equivalent nonlinear model is usually applied in seismic response analysis.The shear modulus and damping ratio are two important properties in this model.Highly weathered granite is common in large engineering.It is essential to study dynamic properties of highly weathered granite.The shear modulus and damping ratio of highly weathered granite are studied with GDS resonant-column;as its the capability is excellent,it is popular in the world.The confining pressure and pore water pressure to consolidate can be controlled well by GDS RCA.After the end of sample' consolidation,shear modulus and damping ratio can be given by experiment in the state of this effective stress.Changing confining pressure and pore water pressure,resonant frequency, shear modulus and damping ratio can be given with another effective stress.In different effective stresses,variation of shear modulus and damping ratio can be observed.And fitting curves of shear modulus and damping ratio that are put forward by Hadin-Drnevich[1] are turned out on the basis of experimental data.The authors discuss the damping mechanism of highly weathered granite sample by amfusing frictional theory.It can be seen that resonance frequency of the sample's system has a positive correlation with shear strain, but sample's damping ratio has a negative with shear strain.The effective stress can have impact on both sample's shear modulus and damping ratio.However,pore water pressure can only act on damping ratio.
Equivalent nonlinear model is usually applied in seismic response analysis.The shear modulus and damping ratio are two important properties in this model.Highly weathered granite is common in large engineering.It is essential to study dynamic properties of highly weathered granite.The shear modulus and damping ratio of highly weathered granite are studied with GDS resonant-column;as its the capability is excellent,it is popular in the world.The confining pressure and pore water pressure to consolidate can be controlled well by GDS RCA.After the end of sample' consolidation,shear modulus and damping ratio can be given by experiment in the state of this effective stress.Changing confining pressure and pore water pressure,resonant frequency, shear modulus and damping ratio can be given with another effective stress.In different effective stresses,variation of shear modulus and damping ratio can be observed.And fitting curves of shear modulus and damping ratio that are put forward by Hadin-Drnevich[1] are turned out on the basis of experimental data.The authors discuss the damping mechanism of highly weathered granite sample by amfusing frictional theory.It can be seen that resonance frequency of the sample's system has a positive correlation with shear strain, but sample's damping ratio has a negative with shear strain.The effective stress can have impact on both sample's shear modulus and damping ratio.However,pore water pressure can only act on damping ratio.
引文
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[10]曹成效,刘乐军,李培英,等.循环荷载作用下粉土的动力学特性[J].海洋科学进展,2007,25(1):54-62.CAO Cheng-xiao,LIU Le-jun,LI Pei-ying,et al.Dynamic characteristics of silty soil under cyclicloadings[J].Advances in Marine Science,2007,25(1):54-62.
[11]蔡辉腾,李英民,欧秉松.福州地区典型土动剪切模量与阻尼比的试验研究[J].岩土力学,2010,31(2):361-365.CAI Hui-teng,LI Ying-min,OU Bing-song.Testing studyof dynamic shear modulus and damping ratio of typicalsoils in Fuzhou area[J].Rock and Soil Mechanics,2010,31(2):361-365.
[12]何晓民,陈志强,张婷.武汉砂土动剪切模量与阻尼比的试验研究[J].世界地震工程,2010,26(增刊):41-45.HE Xiao-min,CHEN Zhi-qiang,ZHANG Ting.Experimental studies on dynamic shear modulus anddamping ratio of sandy soil in Wuhan[J].WorldEarthquake Engineering,2010,26(Supp.):41-45.
[13]American Society for Testing and Materials.D4015-92Standard test methods for modulus and damping of soilsby the resonant-column method[S].United States:ASTMSTP,2000.
[14]YOUN J U,CHOO Y W,KIM D S.Measurement ofsmall-strain shear modulus Gmax of dry and saturatedsands by bender element,resonant column,and torsionalshear tests[J].Canadian Geotechnical Journal,2008,45(10):1426-1438.
[2]孙静.岩土动剪切模量阻尼试验及应用研究[博士学位论文D].哈尔滨:中国地震局工程力学研究所,2004.
[3]蒋通,邢海灵.围压对土动剪模量和阻尼比影响的简化计算方法[J].岩石力学与工程学报,2007,26(7):1432-1437.JIANG Tong,XING Hai-ling.A simple methodconsidering effects of confining pressure on dynamicshear module and damping ratio[J].Chinese Journal ofRock Mechanics and Engineering,2007,26(7):1432-1437.
[4]柏立懂.荷载历史对砂土最大剪切模量影响的共振柱试验研究[J].岩石力学与工程学报,2011,30(11):2366-2374.BAI Li-dong.Effects of loading history on maximumshear modulus of sand by resonant column tests[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(11):2366-2374.
[5]张建民,王稳祥.振动频率对饱和砂土动力特性的影响[J].岩土工程学报,1990,12(1):89-97.
[6]ABALAR A F.Dynamic properties of various plasticityclays[J].The Electronic Journal of GeotechnicalEngineering,2009,B(14):1-11.
[7]KALLIOGLOU P,TIKA T H,PITILAKIS K.ShearModulus and damping ratio of cohesive soils[J].Journalof Earthquake Engineering,2008,12:879-913.
[8]陈国兴,刘雪珠.南京及邻近地区新近沉积土的动剪切模量和阻尼比的试验研究[J].岩石力学与工程学报,2004,23(8):1403-1410.CHEN Guo-xing,LIU Xue-zhu.Testing study on ratio ofdynamic shear module and ratio of damping for recentlydepositon soils in Nanjing and its neighboring areas[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(8):1403-1410.
[9]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.Laboratoryexperimental study on dynamic shear modulus ratio anddamping ratio of soils[J].Earthquake Engineering andEngineering Vibration,2000,20(4):133-139.
[10]曹成效,刘乐军,李培英,等.循环荷载作用下粉土的动力学特性[J].海洋科学进展,2007,25(1):54-62.CAO Cheng-xiao,LIU Le-jun,LI Pei-ying,et al.Dynamic characteristics of silty soil under cyclicloadings[J].Advances in Marine Science,2007,25(1):54-62.
[11]蔡辉腾,李英民,欧秉松.福州地区典型土动剪切模量与阻尼比的试验研究[J].岩土力学,2010,31(2):361-365.CAI Hui-teng,LI Ying-min,OU Bing-song.Testing studyof dynamic shear modulus and damping ratio of typicalsoils in Fuzhou area[J].Rock and Soil Mechanics,2010,31(2):361-365.
[12]何晓民,陈志强,张婷.武汉砂土动剪切模量与阻尼比的试验研究[J].世界地震工程,2010,26(增刊):41-45.HE Xiao-min,CHEN Zhi-qiang,ZHANG Ting.Experimental studies on dynamic shear modulus anddamping ratio of sandy soil in Wuhan[J].WorldEarthquake Engineering,2010,26(Supp.):41-45.
[13]American Society for Testing and Materials.D4015-92Standard test methods for modulus and damping of soilsby the resonant-column method[S].United States:ASTMSTP,2000.
[14]YOUN J U,CHOO Y W,KIM D S.Measurement ofsmall-strain shear modulus Gmax of dry and saturatedsands by bender element,resonant column,and torsionalshear tests[J].Canadian Geotechnical Journal,2008,45(10):1426-1438.
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