双向激振下饱和软黏土动模量与阻尼变化规律试验研究
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摘要
通过GDS双向动三轴系统对双向激振循环荷载作用下饱和软黏土的动模量与阻尼变化规律进行研究。结果表明:随着径向循环应力增加,孔压比增加,双向激振对孔压的影响仅限于对初始孔压的提高,且初始孔压提高的幅度近似与径向循环应力相等;双向激振对门槛循环应力比的影响不明显;径向循环应力对动模量与阻尼的变化规律有显著的影响,在动应变一定的情况下,随着径向循环应力比的增加,动模量降低,阻尼比增加。随着径向循环应力的增加,小应变弹性模量随之减小,且近似与径向循环应力比成线性关系,据此实现了Hardin公式的修正,建立了双向激振下小应变弹性模量经验模型。径向循环应力及围压对(Ed/Edmax)-εd及(D/Dmax)-εd关系曲线影响不明显,通过对双曲线型模型修正,建立双向激振下饱和软黏土动模量与阻尼随动应变变化的经验模型。
Dynamic modulus and damping ratio of saturated soft clay under bidirectional cyclic loading are investigated by GDS dynamic triaxial system. It is observed that the pore water pressure ratio increases significantly with the increase of radial cyclic stress ratio. Radial cyclic stress has great effect on initial pore water pressure;and the increase of initial pore water pressure is approximately equal to the radial cyclic stress. The threshold of cyclic stress ratio changes little under bidirectional cyclic loading. The dynamic modulus and damping ratio are affected by radial cyclic stress significantly. By increasing the radial cyclic stress,the damping ratio increases while the dynamic modulus decreases. Small strain elastic modulus decreases as the radial cyclic stress increases and there is a linear relation between the small strain elastic modulus and the radial cyclic stress ratio. An empirical model for the small strain elastic modulus is obtained based on the modification of Hardin equation. The radial cyclic stress and confining pressure have little effect on the curves of ( Ed / Ed max)- ε d and ( D / Dm ax)- ε d. By modifying hyperbolic model,the empirical models for describing the change of dynamic modulus and damping with dynamic strain are obtained.
Dynamic modulus and damping ratio of saturated soft clay under bidirectional cyclic loading are investigated by GDS dynamic triaxial system. It is observed that the pore water pressure ratio increases significantly with the increase of radial cyclic stress ratio. Radial cyclic stress has great effect on initial pore water pressure;and the increase of initial pore water pressure is approximately equal to the radial cyclic stress. The threshold of cyclic stress ratio changes little under bidirectional cyclic loading. The dynamic modulus and damping ratio are affected by radial cyclic stress significantly. By increasing the radial cyclic stress,the damping ratio increases while the dynamic modulus decreases. Small strain elastic modulus decreases as the radial cyclic stress increases and there is a linear relation between the small strain elastic modulus and the radial cyclic stress ratio. An empirical model for the small strain elastic modulus is obtained based on the modification of Hardin equation. The radial cyclic stress and confining pressure have little effect on the curves of ( Ed / Ed max)- ε d and ( D / Dm ax)- ε d. By modifying hyperbolic model,the empirical models for describing the change of dynamic modulus and damping with dynamic strain are obtained.
引文
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[19]DARENDELI M B.Development of a new family of normalized moduli reduction and material damping curves[Ph.D.Thesis][D].Austin:University of Texas at Austin,2001.
[20]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 Hailing.A simple method considering effects of confining pressure on dynamic shear moduli and damping ratio[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(7):1432–1437.(in Chinese))
[21]马德翠,单红仙,周其健.黄河三角洲粉质土的动模量和阻尼比试验研究[J].工程地质学报,2005,13(3):353–358.(MA Decui,SHAN Hongxian,ZHOU Qijian.Experimental study on shear modulus and damping ratio characteristics of silty soil in the delta of Yellow River[J].Journal of Engineering Geology,2005,13(3):353–358.(in Chinese))
[22]尚守平,卢华喜,任慧,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 Shouping,LU Huaxi,REN Hui,et al.Comparative study on dynamic shear modulus of silty clay[J].Chinese Journal of Geotechnical Engineering,2006,28(3):410–414.(in Chinese))
[23]WU C P,HWANG J H,CHIEN T K.Dynamic properties of saturated compacted soils[C]//Geotechnical Earthquake and Engineering and Soil Dynamics(IV).[S.l.]:[s.n.],2008:1–10.
[2]BOMMER J J,GEORGALLIDES G,TROMANS I J.Is there a near-field for small-to-moderate magnitude earthquakes?[J].Journal of Earthquake Engineering,2001,5(3):395–423.
[3]ZEN K,HIGUCHI Y.Prediction of vibratory shear modulus and damping ratio for cohesive soils[C]//Proceedings of the8th World Conference on Earthquake Engineering.[S.l.]:[s.n.],1984:23–30.
[4]HARDIN B O,BLACK W L.Vibration modulus of normally consolidated clay:design equation and curves[J].Journal of the Soil Mechanics and Foundation Engineering Division,ASCE,1968,94(2):353–369.
[5]蔡袁强,梁旭,李坤.水泥土–土复合试样的动力特性[J].水利学报,2003,(10):19–25.(CAI Yuanqiang,LIANG Xu,LI Kun.Dynamic characteristics of composite sample of cemented clay-clay[J].Journal of Hydraulic Engineering,2003,(10):19–25.(in Chinese))
[6]蔡袁强,王军,海钧.双向激振循环荷载作用下饱和软黏土强度和变形特性研究[J].岩石力学与工程学报,2008,27(3):495–504.(CAI Yuanqiang,WANG Jun,HAI Jun.Study of strength and deformation behaviors of soft clay under bidirectional exciting cyclic loading[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):495–504.(in Chinese))
[7]MATSUI T,ITO T,OHARA H.Cyclic stress-strain history and shear characteristic of clays[J].Journal of the Geotechnical Engineering Division,ASCE,1980,106(10):1101–1120.
[8]周建,龚晓南.循环荷载作用下饱和软黏土应变软化研究[J].土木工程学报,2000,33(5):62–68.(ZHOU Jian,GONG Xiaonan.Study on strain soff in saturated soft clay under cyclic loading[J].China Civil Engineering Journal,2000,33(5):62–68.(in Chinese))
[9]OHARA S,MATSUDA H.Study on the settlement of saturated clay layer induced by cyclic shear[J].Soils and Foundations,1988,28(3):103–113.
[10]VUCETIC M.Cyclic threshold shear strains in soils[J].Journal of Geotechnical Engineering,1994,120(12):2208–2228.
[11]周建,龚晓南,李剑强.循环荷载作用下饱和软黏土特性试验研究[J].工业建筑,2000,30(11):430–441.(ZHOU Jian,GONG Xiaonan,LI Jianqiang.Experimental study of saturated soft clay under cyclic loading[J].Industrial Construction,2000,30(11):430–441.
[12]齐剑峰,栾茂田,杨庆,等.饱和黏土动剪切模量与阻尼比的试验研究[J].岩土工程学报,2008,30(4):518–523.(QI Jianfeng,LUAN Maotian,YANG Qing,et al.Dynamic shear modulus and damping ratio of saturated clay[J].Chinese Journal of Geotechnical Engineering,2008,30(4):518–523.(in Chinese))
[13]ZHANG J F,ANDRUS R D,JUANG C H.Normalized shear modulus and material damping ratio relationships[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(4):453–464.
[14]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):353–369.
[15]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):73–84.(CHEN Guoxing,XIE Junfei,ZHANG Kexu.The empirical evaluation of soil moduli and damping ratio for dynamic analysis[J].Earthquake Engineering and Engineering Vibration,1995,15(1):73–84.(in Chinese))
[16]LAMBE T W,WHITMAN R V.Soil mechanics[M].New York:John Wiley and Sons,Inc.,1969.
[17]HITCHER P Y,EL HOSRI M S,HOMSI M.Cyclic properties of soils within a large range of strain amplitude[C]//Developments in Geotechnical Engineering(Vol.42):Soil Dynamics and Liquefaction.New York:Elsevier,1987:365–378.
[18]梁旭.水泥搅拌桩复合地基动力特性及其与上部结构动力作用研究[博士学位论文][D].杭州:浙江大学,2003.(LIANG Xu.Study on dynamic properties of cement mixed pile foundations and the soil-structure interactions during earthquakes[Ph.D.Thesis][D].Hangzhou:Zhejiang University,2003.(in Chinese))
[19]DARENDELI M B.Development of a new family of normalized moduli reduction and material damping curves[Ph.D.Thesis][D].Austin:University of Texas at Austin,2001.
[20]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 Hailing.A simple method considering effects of confining pressure on dynamic shear moduli and damping ratio[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(7):1432–1437.(in Chinese))
[21]马德翠,单红仙,周其健.黄河三角洲粉质土的动模量和阻尼比试验研究[J].工程地质学报,2005,13(3):353–358.(MA Decui,SHAN Hongxian,ZHOU Qijian.Experimental study on shear modulus and damping ratio characteristics of silty soil in the delta of Yellow River[J].Journal of Engineering Geology,2005,13(3):353–358.(in Chinese))
[22]尚守平,卢华喜,任慧,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 Shouping,LU Huaxi,REN Hui,et al.Comparative study on dynamic shear modulus of silty clay[J].Chinese Journal of Geotechnical Engineering,2006,28(3):410–414.(in Chinese))
[23]WU C P,HWANG J H,CHIEN T K.Dynamic properties of saturated compacted soils[C]//Geotechnical Earthquake and Engineering and Soil Dynamics(IV).[S.l.]:[s.n.],2008:1–10.
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