循环荷载作用下结构性软黏土动力特性试验研究
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摘要
循环荷载作用下软土力学参数呈现衰减劣化的趋势。本文以天津滨海海积软土为研究对象,通过GCTS空心圆柱扭剪仪进行不同波形与幅值动力循环试验,在达到规定振次后停止试验,利用微型十字板测试其抗剪强度,根据典型的动应力-应变滞回曲线确定动压缩模量、阻尼比与动应变的关系。试验结果表明:循环荷载作用下,累积变形量、抗剪强度、动压缩模量、阻尼比演化与波形和幅值有关。幅值相同时,方波产生的累积变形量明显大于正弦波。低幅值时,抗剪强度基本上表现为随振次增加先下降明显,后趋于稳定,与变形一致,属于稳定型;临界应力幅值时,随着振次增加,开始强度下降幅度大,之后下降速率变小,但不趋于稳定。动压缩模量变化趋势与十字板强度演化规律一致,阻尼比变化特征与十字板强度变化呈相反的趋势。
The mechanical parameters of soft clay under cyclic loading present the trend of degradation. The marine? soft? clay of Tianjin Binhai is taken as the research object in this paper. Dynamic cycling test with different wave patterns and amplitudes was carried out by hollow cylinder torsional apparatus( GCTS) and stopped after reaching the specified vibration times. The miniature vane shear tester was used to test the shear strength. According to the typical dynamic stress-strain hysteretic curve,the relationship between dynamic compression modulus,damping ratio and dynamic strain was determined. The results show that cumulative deformation,shear strength,dynamic compression modulus and damping ratio are related to the waveform and amplitude under cyclic loading.Under the same amplitude,the cumulative deformation of square wave is greater than that of sine wave. With the increase of the vibration times,the shear strength decrease first and then become stable under the low amplitude. It is consistent with the deformation and belongs to stable type. When close to the critical stress amplitude,the shear strength decrease obviously in the start and then decrease slowly with the increase of vibration times,but it does not tend to be stable. The change trend of dynamic compression modulus is accord with the evolution law of vane shear strength,but the variation of damping ratio and vane strength is contrary.
The mechanical parameters of soft clay under cyclic loading present the trend of degradation. The marine? soft? clay of Tianjin Binhai is taken as the research object in this paper. Dynamic cycling test with different wave patterns and amplitudes was carried out by hollow cylinder torsional apparatus( GCTS) and stopped after reaching the specified vibration times. The miniature vane shear tester was used to test the shear strength. According to the typical dynamic stress-strain hysteretic curve,the relationship between dynamic compression modulus,damping ratio and dynamic strain was determined. The results show that cumulative deformation,shear strength,dynamic compression modulus and damping ratio are related to the waveform and amplitude under cyclic loading.Under the same amplitude,the cumulative deformation of square wave is greater than that of sine wave. With the increase of the vibration times,the shear strength decrease first and then become stable under the low amplitude. It is consistent with the deformation and belongs to stable type. When close to the critical stress amplitude,the shear strength decrease obviously in the start and then decrease slowly with the increase of vibration times,but it does not tend to be stable. The change trend of dynamic compression modulus is accord with the evolution law of vane shear strength,but the variation of damping ratio and vane strength is contrary.
引文
[1]闫澍旺,封晓伟,田俊峰.循环荷载下滨海软黏土孔压发展规律及强度弱化特征[J].中国港湾建设,2010,169:86-89.YAN Shuwang,FENG Xiaowei,TIAN Junfeng.Pore pressure development and strength softening character of littoral soft clay under cyclic'oading[J].China Harbour Engineering,2010,169:86-89.(in Chinese)
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[9]Matsui T,Ohara H.Ito T.Cyclic Stress-Strain History and Shear Characteristics of Clay[J].Journal of Geotechnical and Geoenvironmental Engineering.1980,106(80):1101-1120.
[10]王常晶,姬美秀,陈云敏.列车荷载作用下饱和软黏土地基的附加沉降[C]//中国土木工程学会第九届土力学及岩土工程学术会议论文集(下册),2003.WANG Changjing,JI Meixiu,CHEN Yunmin.Additional settlement of satumted soft clay foundation under train load[C]∥Proceedings of the9th National Conference on Soil Mechanics and Geotechnical Engineering of the China Society of Civtl Engineering(Part ii),2003.
[11]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):75-78.ZHOU Jian,GONG Xiaonan.Study on strain in saturated soft clay under cyclic loading[J].China Civil Engineering Journal,2000,33(5):75-78.(in Chinese)
[12]曹勇,孔令伟,杨爱武.海积结构性软土动力性状的循环荷载波形效应与刚度软化特征[J].岩土工程学报,2013,35(3):583-589.CAO Yong,KONG Lingwei,YANG Aiwu.Waveform effect of cyclic loading of dynamic character and stiffness degradation characteristics of marine deposited natural soft clay[J].Chinese Journal of Geotechnical Engineering,2013,35(3):583-589.(in Chinese)
[13]孟令福.微型十字板的应用实践[J].水文地质工程地质,2004,31(5):112-112.MENG Lingfu.Application practice of miniature vane[J].Hydrogeology&Engineering Geology,2004,31(5):112-112.(in Chinese)
[14]贾文祥.微型十字板剪力仪在软土测试中的应用[J].水文地质工程地质,1986(6):16,46-47.JIA Wenxiang.Miniature vane shear test instrument in soft soil applications[J].Hydrogeology&Engineering Geology,1986(6):16,46-47.(in Chinese)
[2]黄茂松,李进军,李兴照.饱和软黏土的不排水循环累积变形特性[J].岩土工程学报,2006,28(7):891-895.HUANG Maosong,LI Jinjun,LI Xingzhao.Cumulative deformation behaviour of soft clay in cyclic undrained tests[J].Chinese Journal of Geotechnical Engineering,2006,28(7):891-895.(in Chinese)
[3]刘胜群,吴建奇.循环荷载作用下软黏土应变软化现象试验研究[J].铁道建筑,2006(5):55-57.LIU Shengqun,WU Jianqi.Study on strain softening behavior of saturated soft clay under cyclic loading[J].Railway Engineering,2006(5):55-57.(in Chinese)
[4]蒋小权.循环作用下黏土应变软化研究[J].地质灾害与环境保护,2016,27(1):65-69.JIANG Xiaoquan.Caly strainsoftening research[J].Journal of Geological Hazards and Environment Preservation,2016,27(1):65-69.(in Chinese)
[5]汪明元,单治钢,王亚军,等.应变控制下舟山岱山海相软土动弹性模量及阻尼比试验研究[J].岩石力学与工程学报,2014,33(7):1503-1512.WANG Mingyuan,SHAN Zhigang,WANG Yajun,et al.Dynamic elastic moduli and damping ratios of marine sediments at Zhou Shan Dai Shan based on dynamic triaxial tests under strain control[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(7):1503-1512.(in Chinese)
[6]刘飞禹,蔡袁强,徐长节,等.循环荷载下软土动弹性模量衰减规律研究[J].浙江大学学报:工版,2008,42(9):1479-1483.LIU Feiyu,CAI Yuanqiang,XU Changjie,et al.WANG Jun.Degradation of dynamic elastic modulus of soft clay under cyclic loading[J].Journal of Zhejiang University:Engineering Science,2008,42(9):1479-1483.(in Chinese)
[7]Brewer J H.The Response of Cyclic Stress in a Normally Consolidated Saturated Clay[D].USA,North Carolina State University,1972.
[8]王元战,焉振.循环荷载下天津软黏土不排水强度弱化模型研究及应用[J].天津大学学报:自然科学与工程技术版,2015(4):347-354.WANG Yuanzhan,YAN Zhen.Research on and Application of Undrained Strength Softening Model of Tianjin Soft Clay Under Cyclic Loading.[J].Journal of Tianjin University:Science and Technology,2015(4):347-354.(in Chinese)
[9]Matsui T,Ohara H.Ito T.Cyclic Stress-Strain History and Shear Characteristics of Clay[J].Journal of Geotechnical and Geoenvironmental Engineering.1980,106(80):1101-1120.
[10]王常晶,姬美秀,陈云敏.列车荷载作用下饱和软黏土地基的附加沉降[C]//中国土木工程学会第九届土力学及岩土工程学术会议论文集(下册),2003.WANG Changjing,JI Meixiu,CHEN Yunmin.Additional settlement of satumted soft clay foundation under train load[C]∥Proceedings of the9th National Conference on Soil Mechanics and Geotechnical Engineering of the China Society of Civtl Engineering(Part ii),2003.
[11]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):75-78.ZHOU Jian,GONG Xiaonan.Study on strain in saturated soft clay under cyclic loading[J].China Civil Engineering Journal,2000,33(5):75-78.(in Chinese)
[12]曹勇,孔令伟,杨爱武.海积结构性软土动力性状的循环荷载波形效应与刚度软化特征[J].岩土工程学报,2013,35(3):583-589.CAO Yong,KONG Lingwei,YANG Aiwu.Waveform effect of cyclic loading of dynamic character and stiffness degradation characteristics of marine deposited natural soft clay[J].Chinese Journal of Geotechnical Engineering,2013,35(3):583-589.(in Chinese)
[13]孟令福.微型十字板的应用实践[J].水文地质工程地质,2004,31(5):112-112.MENG Lingfu.Application practice of miniature vane[J].Hydrogeology&Engineering Geology,2004,31(5):112-112.(in Chinese)
[14]贾文祥.微型十字板剪力仪在软土测试中的应用[J].水文地质工程地质,1986(6):16,46-47.JIA Wenxiang.Miniature vane shear test instrument in soft soil applications[J].Hydrogeology&Engineering Geology,1986(6):16,46-47.(in Chinese)