原状黄土各向异性及卸载变形特征试验研究
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摘要
为揭示原状黄土的各向异性和卸载变形特征,从水平和竖向2个方向取样,通过湿陷性试验、压缩试验、直接剪切试验、三轴剪切试验和卸荷三轴试验,对郑西客运专线贺家庄隧道出口洞顶Q3黄土进行黄土各向异性及卸载变形特征试验研究。结果表明:黄土的竖向和水平方向力学指标有明显差异,竖向和水平方向的压缩模量E1~2平均值分别为5.82和6.83MPa;黄土竖向湿陷性系数平均值为0.026,明显大于水平湿陷性系数平均值0.019;抗剪强度参数中水平向黏聚力大于竖向黏聚力,内摩擦角变化不大;黄土的卸荷变形与主应力差呈线性变化规律,当主应力差减小至0~90kPa时,迅速发生破坏,破坏时应变为0.5%~3.5%;原状黄土的破坏具有突变性,主要表现在卸荷破坏变形很小,破坏变形时间短,速度快。
To investigate the anisotropy and the unloading deformation characteristics of intact loess,a series of laboratory tests,including collapsibility test,compression test,direct shear test,triaxial shear test and unloading triaxial compression test,were carried out,in which the Q3 loess was sampled from the level and vertical directions at the roof in Hejiazhuang tunnel exit of Zhengzhou-Xian passenger dedicated line.The results show that there is significant difference between the vertical and level mechanical properties of loess.The average value of the level and vertical compression modulus E1~2is 6.83 and 5.82 MPa respectively.The average value of vertical collapsibility coefficient is 0.026,which is obviously greater than the lateral one with the value of 0.019.For the parameters of shear strength,the lateral cohesion is greater than the vertical one,the internal friction angle varies little.The unloading deformation of loess changes linearly with the principal stress difference.Failure will occur rapidly when the principal stress difference is reduced to 0~90kPa with the strain between 0.5% ~3.5%.The failure of the intact loess has mutagenicity due to small unloading deformation,short failure time and quick failure speed.
To investigate the anisotropy and the unloading deformation characteristics of intact loess,a series of laboratory tests,including collapsibility test,compression test,direct shear test,triaxial shear test and unloading triaxial compression test,were carried out,in which the Q3 loess was sampled from the level and vertical directions at the roof in Hejiazhuang tunnel exit of Zhengzhou-Xian passenger dedicated line.The results show that there is significant difference between the vertical and level mechanical properties of loess.The average value of the level and vertical compression modulus E1~2is 6.83 and 5.82 MPa respectively.The average value of vertical collapsibility coefficient is 0.026,which is obviously greater than the lateral one with the value of 0.019.For the parameters of shear strength,the lateral cohesion is greater than the vertical one,the internal friction angle varies little.The unloading deformation of loess changes linearly with the principal stress difference.Failure will occur rapidly when the principal stress difference is reduced to 0~90kPa with the strain between 0.5% ~3.5%.The failure of the intact loess has mutagenicity due to small unloading deformation,short failure time and quick failure speed.
引文
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[11]邵生俊.原状黄土的结构性强度特性及其在黄土隧道围岩压力分析中的应用[J].土木工程学报,2008,41(11):93-98.(SHAO Shengjun.The Strength Characteristics of Loess with Different Structures and Its Application in Analyzing the Earth Pressure on Loess Tunnel[J].China Civil Engineering Journal,2008,41(11):93-98.in Chinese)
[12]龚晓南.高等土力学[M].杭州:浙江大学出版社,1996:282-286.
[13]MITSUTOSHI Yoshimine.Mechanical Anisotropy of Undisturbed Loess Soil[C]//软土地区岩土工程新进展—中日岩土工程学术会议论文集.上海:同济大学出版社,2005:150-157.(MITSUTOSHI Yoshimine.Mechanical Anisotropy of Undisturbed Loess Soil[C]//Geotechnical Engineering Progress of the Soft Soil Area-Sino-Japanese Geotechnical Engineering Conference Proceedings.Shanghai:Tongji University Press,2005:150-157.in Chinese)
[14]张茂花,谢永利,刘保健.湿陷性黄土变形的各向异性及与浸水路径的无关性[J].中国公路学报,2006,19(4):11-16.(ZHANG Maohua,XIE Yongli,LIU Baojian.Anisotropy of Collapsible Loess Deformation and Independence of Deformation and Soak Paths[J].China Journal of Highway and Transport,2006,19(4):11-16.in Chinese)
[15]安亚芳,梁庆国,赵磊,等.兰州Q4黄土力学性质的各向异性初探[J].兰州交通大学学报,2011,30(1):90-96.(AN Yafang,LIANG Qingguo,ZHAO Lei,et al.Preliminary Research on Anisotropy of Mechanical Properties of Q4 Loess in Lanzhou[J].Journal of Lanzhou Jiaotong University,2011,30(1):90-96.in Chinese)
[2]李家春,田伟平.黄土路堤坡顶及土路肩暴雨冲蚀破坏机理试验[J].长安大学学报:自然科学版,2004,24(2):27-29.(LI Jiachun,TIAN Weiping.Rainfall Erode Mechanism on Loess Road Shoulder and Top of Side-Slope[J].Journal of Changan University:Natural Science Edition,2004,24(2):27-29.in Chinese)
[3]刘祖典.黄土力学与工程[M].西安:陕西科学技术出版社,1997:19-59.
[4]赵占厂,谢永利,杨晓华,等.黄土公路隧道衬砌受力特性测试研究[J].中国公路学报,2004,17(1):66-69(ZHAO Zhanchang,XIE Yongli,YANG Xiaohua,et al.Observation Research on the Mechanical Characteristic of Highway Tunnel Lining in Loess[J].China Journal of Highway and Transport,2004,17(1):66-69.in Chinese)
[5]谢定义.试论我国黄土力学研究中的若干新趋向[J].岩土工程学报,2001,23(1):3-13(XIE Dingyi.Exploration of Some New Tendencies in Research of Loess Soil Mechanics[J].Chinese Journal of Geotechnical Engineering,2001,23(1):3-13.in Chinese)
[6]中国科学院土木建筑研究所土力学研究室.黄土基本性质的研究[M].北京:科学出版社,1961:25-33.
[7]王永焱,林在贯.中国黄土的结构特征及物理力学性质[M].北京:科学出版社,1990:105-107.
[8]齐吉琳,谢定义,石玉成.土结构性的研究方法及现状[J].西北地震学报.2001,23(1):99-103.(QI Jilin,XIE Dingyi,SHI Yucheng.Status Quo and Method of Quantitative Study on Soil Structure[J].Northwestern Seismological Journal,2001,23(1):99-103.in Chinese)
[9]谢定义,齐吉琳,朱元林.土的结构性参数及其与变形强度的关系[J].水利学报,1999(10):1-6.(XIE Dingyi,QI Jilin,ZHU Yuanlin.Soil Structure Parameter and Its Relations to Deformation and Strength[J].Journal of Hydraulic Engineering,1999(10):1-6.in Chinese)
[10]邵生俊,周飞飞,龙吉勇.原状黄土结构性及其定量化参数研究[J].岩土工程学报,2004,26(4):531-536.(SHAO Shengjun,ZHOU Feifei,LONG Jiyong.Structural Properties of Loess and Its Quantitative Parameter[J].Chinese Journal of Geotechnical Engineering,2004,26(4):531-536.in Chinese)
[11]邵生俊.原状黄土的结构性强度特性及其在黄土隧道围岩压力分析中的应用[J].土木工程学报,2008,41(11):93-98.(SHAO Shengjun.The Strength Characteristics of Loess with Different Structures and Its Application in Analyzing the Earth Pressure on Loess Tunnel[J].China Civil Engineering Journal,2008,41(11):93-98.in Chinese)
[12]龚晓南.高等土力学[M].杭州:浙江大学出版社,1996:282-286.
[13]MITSUTOSHI Yoshimine.Mechanical Anisotropy of Undisturbed Loess Soil[C]//软土地区岩土工程新进展—中日岩土工程学术会议论文集.上海:同济大学出版社,2005:150-157.(MITSUTOSHI Yoshimine.Mechanical Anisotropy of Undisturbed Loess Soil[C]//Geotechnical Engineering Progress of the Soft Soil Area-Sino-Japanese Geotechnical Engineering Conference Proceedings.Shanghai:Tongji University Press,2005:150-157.in Chinese)
[14]张茂花,谢永利,刘保健.湿陷性黄土变形的各向异性及与浸水路径的无关性[J].中国公路学报,2006,19(4):11-16.(ZHANG Maohua,XIE Yongli,LIU Baojian.Anisotropy of Collapsible Loess Deformation and Independence of Deformation and Soak Paths[J].China Journal of Highway and Transport,2006,19(4):11-16.in Chinese)
[15]安亚芳,梁庆国,赵磊,等.兰州Q4黄土力学性质的各向异性初探[J].兰州交通大学学报,2011,30(1):90-96.(AN Yafang,LIANG Qingguo,ZHAO Lei,et al.Preliminary Research on Anisotropy of Mechanical Properties of Q4 Loess in Lanzhou[J].Journal of Lanzhou Jiaotong University,2011,30(1):90-96.in Chinese)
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