土体三维卸荷弹塑性模型及其试验验证
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摘要
天然土体经历开挖卸荷应力路径后,其应力变形特性与常规加载应力路径条件下规律存在较大差异。目前常用土体本构模型大多建立在等向固结单向加载三轴试验基础上,没有考虑初始K_0固结和开挖卸荷应力路径的影响。以剑桥模型为基础,借鉴关口-太田模型的建模思想,通过引入新的应力比参数,对p-q平面上屈服轨迹硬化轴进行旋转,调整弹性区范围,以反映初始K_0固结的影响;再运用变换应力法将模型三维化处理,从而使模型可以描述土体三向不等向应力状态,最终得到一个能综合反映土体K_0固结开挖卸荷应力-应变特性的三维弹塑性本构模型。通过和典型室内应力路径试验结果进行对比,验证了模型的合理性。
When the natural soil is influenced by the unloading induced by the excavation, its stress-strain relationship shows a quite difference with the relationships obtain from the conventional loading test of undisturbed natural soil. At present, commonly applied soil constitutive models are established based on the conventional tri-axial test, where soil is subjected to isotropic confine pressure and uni-axial loading stress. In addition, these constitutive models do not take the influence of initial K_0 consolidation and the unloading induced by excavation into consideration. In this paper, a new model is proposed based on the Cam-clay model and the principles of Ohta-Sekiguchi model. In the proposed model, to adjust the elastic region and reflect the influence of the initial K_0 consolidation, the hardening axis in p–q stress space is rotated by introducing a stress ratio. To describe the three-dimensional anisotropic stress state, the transformation stress method is introduced to the model. By all these approaches above, this newly proposed model is able to reasonably describe the strength and deformation of soil under initial K_0 stress and complex stress-train relationships under unloading induced by excavation. The rationality of this proposed model is verified by comparing the predicted results with the results obtained from typical laboratory tests.
When the natural soil is influenced by the unloading induced by the excavation, its stress-strain relationship shows a quite difference with the relationships obtain from the conventional loading test of undisturbed natural soil. At present, commonly applied soil constitutive models are established based on the conventional tri-axial test, where soil is subjected to isotropic confine pressure and uni-axial loading stress. In addition, these constitutive models do not take the influence of initial K_0 consolidation and the unloading induced by excavation into consideration. In this paper, a new model is proposed based on the Cam-clay model and the principles of Ohta-Sekiguchi model. In the proposed model, to adjust the elastic region and reflect the influence of the initial K_0 consolidation, the hardening axis in p–q stress space is rotated by introducing a stress ratio. To describe the three-dimensional anisotropic stress state, the transformation stress method is introduced to the model. By all these approaches above, this newly proposed model is able to reasonably describe the strength and deformation of soil under initial K_0 stress and complex stress-train relationships under unloading induced by excavation. The rationality of this proposed model is verified by comparing the predicted results with the results obtained from typical laboratory tests.
引文
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[6]张艳刚,张坤勇,史峤臻.开挖卸荷土体本构模型研究方法[J].水利与建筑工程学报, 2010, 8(4):40-43.ZHANG Yan-gang, ZHANG Kun-yong, SHI Qiao-zhen.Researchmethodofconstitutivemodelforexcavation unloading soil mass[J]. Journal of Water Resources and Architectural Engineering, 2010, 8(4):40-43.
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[10]韩国城,连镇营,姚仰平.一个适用于深基坑开挖的三维各向异性模型[J].水利学报, 2002, 33(11):14-19.HAN Guo-cheng, LIAN Zhen-ying, YAO Yang-ping. 3D anisotropicmodelforsimulationofsoilindeep excavationpit[J].JournalofHydraulicEngineering,2002, 33(11):14-19.
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[13]张坤勇,梅国雄,赵延勇.关于土体各向异性弹塑性模型的讨论[J].河海大学学报(自然科学版), 2006, 34(4):451-455.ZHANGKun-yong,MEIGuo-xiong,ZHAOYan-yong.Discussion of anisotropic elasto-plastic model for soil[J].Journal of Hohai University(Natural Sciences), 2006,34(4):451-455.
[14]张坤勇,陈芸,梅国雄.土体各向异性弹塑性模型的改进[J].水利水电科技进展, 2006, 26(6):51-53, 57.ZHANGKun-yong,CHENYun,MEIGuo-xiong.Modification of anisotropic elastoplastic model for soil[J].Advances in Science and Technology of Water Resoures,2006, 26(6):51-53, 57.
[15]NORIYUKIYASUFUXU,HIDEKAZUMURATA,HYODOMASAYUKI.Yieldcharacteristicsof anisotropicallyconsilidatedsandunderlowandhigh stresses[J].SoilsandFoundations,1991,1(31):95-109.
[16]CALLISTO L, CALABRESI G. Mechanical behaviour of a natural soft clay[J]. Geotechnique, 1998, 48(4):495-513.
[17]张坤勇.考虑应力各向异性土体本构模型及其应用研究[D].南京:河海大学, 2004.ZHANGKun-yong.Studyandapplicationonsoil’s constitutivemodelwiththeconsiderationofstressinduced anisotropy[D]. Nanjing:Hohai University, 2004.
[18]袁聚云.软土各向异性性状的试验研究及其在工程中的应用[D].上海:同济大学, 1995.YUANJu-yun.Experimentalstudyonanisotropic properties of soft soil and its application in Engineering[D].Shanghai:Tongji University, 1995.
[19]ICHIHARA W. Deformation and strength characteristics ofintermediatesoilundertriaxialstresscondition[R].Nagoya:Bachelor’sThesisatNagoyaInstituteof Technology, 1997.
[2]DUNCANJM,BYRNEP,WONGK.Strength stress-strainandbulkmodulusparametersforfinite elementanalysisofstressessandmovementsinsoil masses[R].[S. l.]:[s. n.], 1980.
[3]ROSCOE K H, SCHOFIELD A N, WROTH C P. On the yielding of soils[J]. Geotechnique, 1958, 8(1):22-53.
[4]ROSCOEKH,BURLANDJB.Onthegeneralized stress-strainbehaviourofwetclay[M]//Engineering Plasticity. Cambridge:Cambridge University Press, 1968:535-609
[5]殷宗泽.一个土体的双屈服面应力-应变模型[J].岩土工程学报, 1988, 10(4):64-71.YIN Zong-ze. A Double yield surfaces stress-strain model ofsoil[J].ChineseJournalofGeotechnical Engineering, 1988, 10(4):64-71.
[6]张艳刚,张坤勇,史峤臻.开挖卸荷土体本构模型研究方法[J].水利与建筑工程学报, 2010, 8(4):40-43.ZHANG Yan-gang, ZHANG Kun-yong, SHI Qiao-zhen.Researchmethodofconstitutivemodelforexcavation unloading soil mass[J]. Journal of Water Resources and Architectural Engineering, 2010, 8(4):40-43.
[7]SEKIGUCHI H, OHTA H. Induced anisotropy and time dependencyinclays[C]//Proceedingsof9thICSMFE.Tokyo:University of Tokyo, 1977, 4(1):229-238.
[8]刘国彬,侯学渊.软土的卸荷模量[J].岩土工程学报,1996, 18(6):22-27.LIU Guo-bin, HOU Xue-yuan. Unloading modulus of the Shanghai soft clay[J]. Chinese Journal of Geotechnical Engineering, 1996, 18(6):22-27.
[9]孙德安,姚仰平,殷宗泽.初始应力各向异性土的弹塑性模型[J].岩土力学, 2000, 21(3):222-226.SUNDe-an,YAOYang-ping,YINZong-ze.An elasto-plasticmodel forsoilwithinitiallystress-induced anisotropy[J].RockandSoilMechanics,2000,21(3):222-226.
[10]韩国城,连镇营,姚仰平.一个适用于深基坑开挖的三维各向异性模型[J].水利学报, 2002, 33(11):14-19.HAN Guo-cheng, LIAN Zhen-ying, YAO Yang-ping. 3D anisotropicmodelforsimulationofsoilindeep excavationpit[J].JournalofHydraulicEngineering,2002, 33(11):14-19.
[11]魏星,黄茂松.软土初始应力各向异性弹塑性模型[J].岩土力学, 2004, 25(增刊2):43-46.WEIXing,HUANGMao-song.Anelastoplasticmodel forsoftclayswithinitiallystress-inducedanisotropy[J].Rock and Soil Mechanics, 2004, 25(Suppl. 2):43-46.
[12]陈浩,梅国雄,李治.基坑土体侧向卸荷条件下的变形性状研究[J].合肥工业大学学报(自然科学版),2009,32(10):1551-1553.CHENHao,MEIGuo-xiong,LIZhi.Deformation characteristics of the soil around the foundation pit with lateralunloading[J].JournalofHefeiUniversityof Technology(NaturalSciences),2009,32(10):1551-1553.
[13]张坤勇,梅国雄,赵延勇.关于土体各向异性弹塑性模型的讨论[J].河海大学学报(自然科学版), 2006, 34(4):451-455.ZHANGKun-yong,MEIGuo-xiong,ZHAOYan-yong.Discussion of anisotropic elasto-plastic model for soil[J].Journal of Hohai University(Natural Sciences), 2006,34(4):451-455.
[14]张坤勇,陈芸,梅国雄.土体各向异性弹塑性模型的改进[J].水利水电科技进展, 2006, 26(6):51-53, 57.ZHANGKun-yong,CHENYun,MEIGuo-xiong.Modification of anisotropic elastoplastic model for soil[J].Advances in Science and Technology of Water Resoures,2006, 26(6):51-53, 57.
[15]NORIYUKIYASUFUXU,HIDEKAZUMURATA,HYODOMASAYUKI.Yieldcharacteristicsof anisotropicallyconsilidatedsandunderlowandhigh stresses[J].SoilsandFoundations,1991,1(31):95-109.
[16]CALLISTO L, CALABRESI G. Mechanical behaviour of a natural soft clay[J]. Geotechnique, 1998, 48(4):495-513.
[17]张坤勇.考虑应力各向异性土体本构模型及其应用研究[D].南京:河海大学, 2004.ZHANGKun-yong.Studyandapplicationonsoil’s constitutivemodelwiththeconsiderationofstressinduced anisotropy[D]. Nanjing:Hohai University, 2004.
[18]袁聚云.软土各向异性性状的试验研究及其在工程中的应用[D].上海:同济大学, 1995.YUANJu-yun.Experimentalstudyonanisotropic properties of soft soil and its application in Engineering[D].Shanghai:Tongji University, 1995.
[19]ICHIHARA W. Deformation and strength characteristics ofintermediatesoilundertriaxialstresscondition[R].Nagoya:Bachelor’sThesisatNagoyaInstituteof Technology, 1997.