大连饱和黏土动力特性研究
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摘要
利用"土工静力-动力液压三轴-扭转多功能扭剪仪",使用改进的真空抽吸法制备重塑饱和黏土空心试样,采用单独试样振后固结再振(加卸载)的试验方法,探讨了大连饱和黏土的动力特性.试验结果表明:在微小应变下避免孔隙水压力明显升高,使用单独试样通过改变固结压力的方法获得的最大动剪切模量Gmax和阻尼比ξ与用多个试样常规方法获得的结果很接近,是比较可靠的;卸压时的G随固结压力的减小而降低,下降的梯度比加压时的小.试验中将非接触式与接触式角位移计联合使用,以提高微小剪应变的测量精度.试验得到的归一化后的G/Gmax-γ和ξ/ξmax-γ基本落入一个很窄的范围内,并且由G/Gmax-γ和ξ/ξmax-γ关系曲线可用公式估算出G和ξ.采用这种单独试样振后固结再振的方法可以节省取样数量和解决土性不均匀问题,并且在试验结果可靠的基础上能够提供很多便利.
The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform cyclic torsional shear test with hollow cylindrical clay specimen which is prepared by advanced vacuum suction method.The cyclic torsional shear test was conducted to measure dynamic shear modulus and damping ratio of Dalian saturated clay under different confining pressures(including increased and decreased pressure with single specimen)to replace the conventional dynamic characteristics method.Experimental results indicate that special attention should be paid to avoiding the pore water pressure's obvious increase in slight strain.Compared with three samples in three effective confining pressures,the differential of G and ξ between two methods is closed.It is concluded that the maximum dynamic shear modulus Gmax and ξ obtained from single sample of cyclic simple shear test are reliable.It is also shown that the dynamic shear modulus decreases as the pressure reduces and the descending gradient is smaller than that of imposed gradient with increasing pressure.Both the gap sensor and external moment of torque transducer are used to increase the precision of small strain.Variations of normalized G/Gmax-γ and ξ/ξmax-γ curves fall in a narrow band and their discreteness is small.Each G and ξ can be obtained from the equations.Furthermore,this one-sample method can diminish the difference of the sample during experiment and effectively provide convenience with authentic experimental result.
The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform cyclic torsional shear test with hollow cylindrical clay specimen which is prepared by advanced vacuum suction method.The cyclic torsional shear test was conducted to measure dynamic shear modulus and damping ratio of Dalian saturated clay under different confining pressures(including increased and decreased pressure with single specimen)to replace the conventional dynamic characteristics method.Experimental results indicate that special attention should be paid to avoiding the pore water pressure's obvious increase in slight strain.Compared with three samples in three effective confining pressures,the differential of G and ξ between two methods is closed.It is concluded that the maximum dynamic shear modulus Gmax and ξ obtained from single sample of cyclic simple shear test are reliable.It is also shown that the dynamic shear modulus decreases as the pressure reduces and the descending gradient is smaller than that of imposed gradient with increasing pressure.Both the gap sensor and external moment of torque transducer are used to increase the precision of small strain.Variations of normalized G/Gmax-γ and ξ/ξmax-γ curves fall in a narrow band and their discreteness is small.Each G and ξ can be obtained from the equations.Furthermore,this one-sample method can diminish the difference of the sample during experiment and effectively provide convenience with authentic experimental result.
引文
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[5]童华炜,朱博鸿.增湿对黄土动剪切模量及阻尼比的影响[C]//第三届全国土动力学学术会议.上海:同济大学出版社,1990:117-120
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[8]何昌荣.动模量和阻尼的动三轴试验研究[J].岩土工程学报,1997,19(2):39-48
[9]谢定义.土动力学[M].西安:西安交通大学出版社,1988
[10]孙静,袁晓铭.土的动模量和阻尼比研究评述[J].世界地震工程,2003,19(1):88-95
[11]郭莹,刘洋,张小玲,等.确定动模量与阻尼比的试验技术研究[C]//第七届全国土动力学学术会议论文集.北京:清华大学出版社,2006:266-269
[12]王全民,李刚,陈正汉,等.厦门砂土的动力特性研究[J].岩土力学,2005,26(10):1628-1632
[13]齐剑峰,聂影,赵维,等.室内黏土试样制备技术的改进及应用[C]//第24届全国土工测试学术研讨会论文集.郑州:黄河水利出版社,2005:123-126
[14]许成顺.复杂应力条件下饱和砂土剪切特性及本构模型的试验研究[D].大连:大连理工大学,2006
[2]SEED H B,IDRISS I M.Soil modulus and damping factors for dynamic response analyses[R]//Report No.EERC70-10.Berkeley:Earthquake Engineering Research Center,University of California,1970
[3]HARDIN B O,BLACK W L.Vibration modulus of normally consolidated clay[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1968,94(2):94-99
[4]石兆吉,丰万玲,张占吉.土壤动压缩模量的共振柱法测定[J].岩土工程学报,1985,7(6):25-32
[5]童华炜,朱博鸿.增湿对黄土动剪切模量及阻尼比的影响[C]//第三届全国土动力学学术会议.上海:同济大学出版社,1990:117-120
[6]顾尧章.海底黏土的剪切模量[J].岩土工程学报,1995,7(2):29-35
[7]周健,池毓蔚.垃圾土动模量和残余应变试验研究[C]//第八届土力学与岩土工程学术会议论文集.北京:万国学术出版社,1999:593-596
[8]何昌荣.动模量和阻尼的动三轴试验研究[J].岩土工程学报,1997,19(2):39-48
[9]谢定义.土动力学[M].西安:西安交通大学出版社,1988
[10]孙静,袁晓铭.土的动模量和阻尼比研究评述[J].世界地震工程,2003,19(1):88-95
[11]郭莹,刘洋,张小玲,等.确定动模量与阻尼比的试验技术研究[C]//第七届全国土动力学学术会议论文集.北京:清华大学出版社,2006:266-269
[12]王全民,李刚,陈正汉,等.厦门砂土的动力特性研究[J].岩土力学,2005,26(10):1628-1632
[13]齐剑峰,聂影,赵维,等.室内黏土试样制备技术的改进及应用[C]//第24届全国土工测试学术研讨会论文集.郑州:黄河水利出版社,2005:123-126
[14]许成顺.复杂应力条件下饱和砂土剪切特性及本构模型的试验研究[D].大连:大连理工大学,2006
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