主应力轴旋转对土体性状影响的试验进展研究
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摘要
对目前国内外主应力轴旋转条件(包括单向旋转和循环旋转)下土体性状研究的室内试验进行系统的分析与总结,得到以下结论:土体在不排水主应力轴旋转条件下产生孔压积累,这在主应力轴循环旋转中特别显著,且通常大于等剪应力幅度的动三轴或扭剪试验产生的孔压,并可建立与某种应变增量的函数关系,此外孔压开展的速率与程度受到土体原生各向异性的影响,但当试样所受剪应力水平较低时,上述影响的程度减弱。而在主应力轴循环旋转过程中,孔压还与主应力轴的转幅或循环次数等因素有关;主应力轴循环旋转并没有导致有效内摩擦角的显著变化。相当一部分试验结果表明,不论主应力轴旋转时的排水条件如何,只要采用归一化的强度标准,土体后续的抗剪强度并不受主应力轴旋转的影响,但也有一些试验表明,排水条件下主应力轴旋转引起原生各向异性轴的同步旋转,导致同一方向旋转前后的定向抗剪强度不尽相同;土体在主应力轴旋转条件下的主应变增量方向往往介于主应力增量和主应力方向之间,而旋转过程对土体后续加载路径中的应力–应变关系是否产生影响主要依赖于主应力轴旋转过程中产生的应变积累水平。此外,还建议可从孔压、强度、应力–应变关系3个角度出发,进行高剪应力水平、高频率主应力轴旋转试验,并深入研究各个应力因素对主应力轴旋转下土性的影响。
The experiments used to detect the characteristics of soil under the condition of principal stress rotation are analyzed systematically.Some conclusions have been drawn as follows.Under the condition of undrained principal stress rotation the pore pressure is generated and accumulated,which is especially obvious in the cyclic rotation;and the pore pressure is usually larger than that in the dynamic triaxial or torsion shear test at the same level of the shear stress.Besides,the mode of the pore pressure accumulation has a certain functional relationship with some kinds of strains,and is influenced by the inherent anisotropy of soil,but this influence is also inhibited at the low level of the shear stress.During cyclic rotation the pore pressure is also influenced by the rotation amplitude,frequency and cycle times.The cyclic stress rotation does not obviously change the effective internal friction angle of soil,and quite a few tests show that whether the soil has experienced principal stress rotation or not,the normalized shear strength criterion is same.But some results convince that the axis of inherent anisotropy can rotate with the rotation of the principal stress under drained condition,which leads to the different shear strengths before and after rotation.During the principal stress rotation the direction of the principal strain increment is between those of the principal stress and the principal stress increment.The degree to which stress-strain relationship influenced by the principal stress rotation as stress history is mainly dependent on the strain level having accumulated during principal stress rotation.The suggestions to bring pore pressure,strength,and stress-strain relationship into consideration on the further experimental study are also put forward.The higher shear stress level is,the higher frequency tests should be taken and the influences of specified stress factors on the properties of the soil under principal stress rotation need to be further investigated.
The experiments used to detect the characteristics of soil under the condition of principal stress rotation are analyzed systematically.Some conclusions have been drawn as follows.Under the condition of undrained principal stress rotation the pore pressure is generated and accumulated,which is especially obvious in the cyclic rotation;and the pore pressure is usually larger than that in the dynamic triaxial or torsion shear test at the same level of the shear stress.Besides,the mode of the pore pressure accumulation has a certain functional relationship with some kinds of strains,and is influenced by the inherent anisotropy of soil,but this influence is also inhibited at the low level of the shear stress.During cyclic rotation the pore pressure is also influenced by the rotation amplitude,frequency and cycle times.The cyclic stress rotation does not obviously change the effective internal friction angle of soil,and quite a few tests show that whether the soil has experienced principal stress rotation or not,the normalized shear strength criterion is same.But some results convince that the axis of inherent anisotropy can rotate with the rotation of the principal stress under drained condition,which leads to the different shear strengths before and after rotation.During the principal stress rotation the direction of the principal strain increment is between those of the principal stress and the principal stress increment.The degree to which stress-strain relationship influenced by the principal stress rotation as stress history is mainly dependent on the strain level having accumulated during principal stress rotation.The suggestions to bring pore pressure,strength,and stress-strain relationship into consideration on the further experimental study are also put forward.The higher shear stress level is,the higher frequency tests should be taken and the influences of specified stress factors on the properties of the soil under principal stress rotation need to be further investigated.
引文
[1]Arthur J R F,Chua K S,Dunstan T.Dense sand weakened by continuous principal stress direction rotation[J].Geotechnique,1979,29(1):91–96.
[2]Joer H A,Lanier J,Fahey M.Deformation of granular materials due to rotation of principal axes[J].Geotechnique,1998,48(5):605–619.
[3]Ishihara K,Towhata I.Sand response to cyclic rotation of principal stress directions as induced by wave loads[J].Soils and Foundations,1983,23(4):11–26.
[4]Hight D W,Gens A,Symes M J P R.The development of a new hollow cylinder apparatus for investigating the effects of principal stress rotation in soils[J].Geotechnique,1983,33(4):355–383.
[5]Vaid Y P,Sayao A,Hou E,et al.Generalized stress path dependent soil behaviour with a new hollow cylinder tortional apparatus[J].Canadian Geotechnical Journal,1990,27:601–616.
[6]沈瑞福,王洪瑾,周景星.动主应力轴连续旋转下砂土的动强度[J].水利学报,1996,(1):27–33.(Shen Ruifu,Wang Hongjin,Zhou Jingxing.Dynamic strength of sand under cyclic rotation of principal stress directions[J].Journal of Hydraulic Engineering,1996,(1):27–33.(in Chinese))
[7]栾茂田,郭莹,李木国,等.土工静力–动力液压三轴–扭转多功能剪切仪研发及应用[J].大连理工大学学报,2003,43(5):670–675.(Luan Maotian,Guo Ying,Li Muguo,et al.Development and application of soil static and dynamic universal triaxial and torsional shear apparatus[J].Journal of Dalian University of Technology,2003,43(5):670–675.(in Chinese))
[8]Symes M J P R,Gens A,Hight D W.Undrained anisotropy and principal stress rotation in saturated sand[J].Geotechnique,1984,34(1):11–27.
[9]Sivathayalan S,Vaid Y P.Influence of generalized initial state and principal stress rotation on the undrained response of sands[J].Canadian Geotechnical Journal,2002,39:63–76.
[10]Towhata I,Ishihara K.Undrained strength of sand undergoing cyclic rotation of principal stress axes[J].Soils and Foundations,1985,25(2):135–147.
[11]刘元雪,郑颖人.含主应力轴旋转的土体本构关系研究进展[J].力学进展,2000,30(4):597–604.(Liu Yuanxue,Zheng Yingren.Research development of soils constitutive relation involving principal stress axes rotation[J].Advances in Mechanics,2000,30(4):597–604.(in Chinese))
[12]付磊,王洪瑾,周景星.主应力偏转角对砂砾料动力特性影响的试验研究[J].岩土工程学报,2000,22(4):435–440.(Fu Lei,Wang Hongjin,Zhou Jingxing.Effect of the initial rotation angle of principal stress on the dynamic properties of soil[J].Chinese Journal of Geotechnical Engineering,2000,22(4):435–440.(in Chinese))
[13]郭莹,栾茂田,何杨,等.复杂应力条件下饱和松砂孔隙水压力增长特性的试验研究[J].地震工程与工程振动,2004,24(3):139–144.(Guo Ying,Luan Maotian,He Yang,et al.Experimental study on development pattern of shaking-induced pore water pressure of saturated loose sand under complex loading[J].Earthquake Engineering and Engineering Vibration,2004,24(3):139–144.(in Chinese))
[14]Shibuya S,Hight D W.Predictions of pore pressure under undrained cyclic principal stress rotation[A].In:Proceedings of the International Conference on Soil Mechanics and Foundation Engineering[C].[s.l.]:[s.n.],1989.123–126.
[15]郭莹,栾茂田,许成顺,等.主应力方向变化对松砂不排水动强度特性的影响[J].岩土工程学报,2003,25(6):666–670.(Guo Ying,Luan Maotian,Xu Chengshun,et al.Effect of variation of principal stress orientation on undrained dynamic strength behavior of loose sand[J].Chinese Journal of Geotechnical Engineering,2003,25(6):666–670.(in Chinese))
[16]Arthur J R F,Chua K S,Dunstan T,et al.Principal stress rotation:a missing parameter[J].Journal of Geotechnial Engineering Division,1980,106(4):419–433.
[17]Wong R K S,Arthur J R F.Sand sheared by stresses with cyclic variations in direction[J].Geotechnique,1986,36(2):215–226.
[18]Wong R K S,Arthur J R F.Induced and inherent anisotropy in sand[J].Geotechnique,1985,35(4):471–481.
[19]Symes M J P R,Gens A,Hight D W.Drained principal stress rotation in saturated sand[J].Geotechnique,1988,38(1):59–81.
[20]Hong W P,Lade P V.Elasto-plastic behavior of K0-consolidated clay in tortion shear tests[J].Soils and Foundations,1989,29(2):127–140.
[21]Lade P V,Kirkgard M M.Effects of stress rotation and changes of b-values on cross-anisotropic behavior of natural,K0-consolidated soft clay[J].Soils and Foundations,2000,40(6):93–105.
[22]Zdravkovic L,Jardine R J.The effect on anisotropy of rotating the principal stress axes during consolidation[J].Geotechnique,2001,51(1):69–83
[23]Jardine R J,Zdravkovic L,Porovic E.Anisotropic consolidation including principal stress axis rotation:experiments,results and practical implications[A].In:Proceedings of the 14th ICSMFE[C].[s.l.]:[s.n.],1997.2 165–2 168.
[24]Wijewickreme D,Vaid Y P.Behavior of loose sand under simultaneous increase in stress ratio and principal stress rotation[J].Canadian Geotechnical Journal,1993,30:953–964.
[25]Akagi H,Yamamoto H.Stress-dilatancy relation of undisturbed clay under principal axes rotation[A].In:Deformation and Progressive Failure in Geomechanics[C].[s.l.]:[s.n.],1997.211–216.
[26]Gr?be P J.Resilient and permanent deformation of railway foundations under principal stress rotation[Ph.D.Thesis][D].Southampton:University of Southampton,2002.
[27]Symes M J P R,Gens A,Hight D W.Discussion:drained principal stress rotation in saturated sand[J].Geotechnique,1989,39(3):549–552.
[2]Joer H A,Lanier J,Fahey M.Deformation of granular materials due to rotation of principal axes[J].Geotechnique,1998,48(5):605–619.
[3]Ishihara K,Towhata I.Sand response to cyclic rotation of principal stress directions as induced by wave loads[J].Soils and Foundations,1983,23(4):11–26.
[4]Hight D W,Gens A,Symes M J P R.The development of a new hollow cylinder apparatus for investigating the effects of principal stress rotation in soils[J].Geotechnique,1983,33(4):355–383.
[5]Vaid Y P,Sayao A,Hou E,et al.Generalized stress path dependent soil behaviour with a new hollow cylinder tortional apparatus[J].Canadian Geotechnical Journal,1990,27:601–616.
[6]沈瑞福,王洪瑾,周景星.动主应力轴连续旋转下砂土的动强度[J].水利学报,1996,(1):27–33.(Shen Ruifu,Wang Hongjin,Zhou Jingxing.Dynamic strength of sand under cyclic rotation of principal stress directions[J].Journal of Hydraulic Engineering,1996,(1):27–33.(in Chinese))
[7]栾茂田,郭莹,李木国,等.土工静力–动力液压三轴–扭转多功能剪切仪研发及应用[J].大连理工大学学报,2003,43(5):670–675.(Luan Maotian,Guo Ying,Li Muguo,et al.Development and application of soil static and dynamic universal triaxial and torsional shear apparatus[J].Journal of Dalian University of Technology,2003,43(5):670–675.(in Chinese))
[8]Symes M J P R,Gens A,Hight D W.Undrained anisotropy and principal stress rotation in saturated sand[J].Geotechnique,1984,34(1):11–27.
[9]Sivathayalan S,Vaid Y P.Influence of generalized initial state and principal stress rotation on the undrained response of sands[J].Canadian Geotechnical Journal,2002,39:63–76.
[10]Towhata I,Ishihara K.Undrained strength of sand undergoing cyclic rotation of principal stress axes[J].Soils and Foundations,1985,25(2):135–147.
[11]刘元雪,郑颖人.含主应力轴旋转的土体本构关系研究进展[J].力学进展,2000,30(4):597–604.(Liu Yuanxue,Zheng Yingren.Research development of soils constitutive relation involving principal stress axes rotation[J].Advances in Mechanics,2000,30(4):597–604.(in Chinese))
[12]付磊,王洪瑾,周景星.主应力偏转角对砂砾料动力特性影响的试验研究[J].岩土工程学报,2000,22(4):435–440.(Fu Lei,Wang Hongjin,Zhou Jingxing.Effect of the initial rotation angle of principal stress on the dynamic properties of soil[J].Chinese Journal of Geotechnical Engineering,2000,22(4):435–440.(in Chinese))
[13]郭莹,栾茂田,何杨,等.复杂应力条件下饱和松砂孔隙水压力增长特性的试验研究[J].地震工程与工程振动,2004,24(3):139–144.(Guo Ying,Luan Maotian,He Yang,et al.Experimental study on development pattern of shaking-induced pore water pressure of saturated loose sand under complex loading[J].Earthquake Engineering and Engineering Vibration,2004,24(3):139–144.(in Chinese))
[14]Shibuya S,Hight D W.Predictions of pore pressure under undrained cyclic principal stress rotation[A].In:Proceedings of the International Conference on Soil Mechanics and Foundation Engineering[C].[s.l.]:[s.n.],1989.123–126.
[15]郭莹,栾茂田,许成顺,等.主应力方向变化对松砂不排水动强度特性的影响[J].岩土工程学报,2003,25(6):666–670.(Guo Ying,Luan Maotian,Xu Chengshun,et al.Effect of variation of principal stress orientation on undrained dynamic strength behavior of loose sand[J].Chinese Journal of Geotechnical Engineering,2003,25(6):666–670.(in Chinese))
[16]Arthur J R F,Chua K S,Dunstan T,et al.Principal stress rotation:a missing parameter[J].Journal of Geotechnial Engineering Division,1980,106(4):419–433.
[17]Wong R K S,Arthur J R F.Sand sheared by stresses with cyclic variations in direction[J].Geotechnique,1986,36(2):215–226.
[18]Wong R K S,Arthur J R F.Induced and inherent anisotropy in sand[J].Geotechnique,1985,35(4):471–481.
[19]Symes M J P R,Gens A,Hight D W.Drained principal stress rotation in saturated sand[J].Geotechnique,1988,38(1):59–81.
[20]Hong W P,Lade P V.Elasto-plastic behavior of K0-consolidated clay in tortion shear tests[J].Soils and Foundations,1989,29(2):127–140.
[21]Lade P V,Kirkgard M M.Effects of stress rotation and changes of b-values on cross-anisotropic behavior of natural,K0-consolidated soft clay[J].Soils and Foundations,2000,40(6):93–105.
[22]Zdravkovic L,Jardine R J.The effect on anisotropy of rotating the principal stress axes during consolidation[J].Geotechnique,2001,51(1):69–83
[23]Jardine R J,Zdravkovic L,Porovic E.Anisotropic consolidation including principal stress axis rotation:experiments,results and practical implications[A].In:Proceedings of the 14th ICSMFE[C].[s.l.]:[s.n.],1997.2 165–2 168.
[24]Wijewickreme D,Vaid Y P.Behavior of loose sand under simultaneous increase in stress ratio and principal stress rotation[J].Canadian Geotechnical Journal,1993,30:953–964.
[25]Akagi H,Yamamoto H.Stress-dilatancy relation of undisturbed clay under principal axes rotation[A].In:Deformation and Progressive Failure in Geomechanics[C].[s.l.]:[s.n.],1997.211–216.
[26]Gr?be P J.Resilient and permanent deformation of railway foundations under principal stress rotation[Ph.D.Thesis][D].Southampton:University of Southampton,2002.
[27]Symes M J P R,Gens A,Hight D W.Discussion:drained principal stress rotation in saturated sand[J].Geotechnique,1989,39(3):549–552.
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