正常固结原状饱和黏性土的本构模型研究
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摘要
基于扰动状态概念研究了正常固结饱和原状黏性土的本构模型。其中,相对完整状态采用基于原状黏性土的理想非线性弹性本构模型来表征;完全调整状态则是基于临界状态土力学框架,将修正剑桥模型与三剪强度准则相结合而建立的弹塑性本构模型来表征。为了更好地反映黏性土的黏聚力影响,提出了等量代换法和坐标平移法两种处理方法,并作了对比研究。针对基于临界状态土力学框架和扰动状态概念建立的原状土本构模型为平均应力、广义剪应力与体应变、广义剪应变间的关系且无屈服函数显式表达式,提出了一个将其三维化的方法。三维化后的原状黏性土本构模型为空间内6个应力分量和6个应变分量之间的关系,更便于复杂应力状态下的土体变形分析及有限元编程。为验证模型的正确性,对正常固结江西原状饱和红黏土土样作了固结排水和固结不排水条件下的常规三轴压缩试验和K0固结试验,并与模型计算结果作了对比,结果表明:所提模型能够较好地反映江西原状饱和红黏土的力学和变形特性。另外,用所提模型对江西原状饱和红黏土进行了真三轴压缩数值模拟实验,探讨了中间主应力对其力学和变形特性的影响,结果表明:中间主应力及其影响系数对土的变形、孔隙水压力、强度均有影响;固结不排水条件下,在相同剪应力的作用下,土体剪应变随中间主应力影响系数的增大而减小,在相同轴向应变条件下,孔隙水压力随中间主应力影响系数的增大而增大;固结排水条件下,在相同平均正应力作用下,土体体应变随中间主应力影响系数的增大而减小,在相同轴向应变条件下,土体体应变随中主应力影响系数的增大而增大。
The triple-shear unified structured constitutive model is proposed for the undisturbed saturated clay in normal consolidation based on the disturbed state concept, in which the relative intact state is characterized by the non-linear elastic model, and the fully adjusted state is characterized by the elasto-plastic model built with the combination of the triple-shear failure criterion and the modified cam-clay model in the critical state soil mechanics. In order to describe the influences of the cohesion on the soil mechanical properties better, two treatments of the equivalent substitution and the coordinate translation are presented and are compared each other. The proposed model may overcome the shortcomings of the modified cam-clay model with the definite failure stress ratio without considering the soil cohesion, which can't reflect the practical differences of strength properties under different stress states and soil cohesion. The advantage is that the new model shows the practical effects under the different stress states acting on the saturated structured clay with different cohesion better. It features that it can describe the effects of intermediate principal stress, rang changes of stress and difference between tension and compression. Because the given structured constitutive model was built on the disturbed state concept and the critical state soil inmechanics is expressed as the stress-strain relations between the mean stress and the generalized shear stress and the bulk strain and the generalized shear strain, and there is no explicit formulation for the yielding function, a three-dimensionalized method is proposed for the previously given model. The three-dimensionalized structured constitutive model for the undisturbed clay may give relations among the six stress components and the six strain components under the complex stress or strain states, for which it is convenient to use in the practical geotechnical deformation analysis and in the finite element method coding. In order to verify the model proposed here, comparisons between the numerical simulations and experimental results under conventional tri-axial compression and K0 consolidation on the Jiangxi undisturbed lateritic clay are made and it shows that the proposed model could reflect the mechanical and deformation characteristics of the Jiangxi undisturbed lateritic clay well. Otherwise, the influences of the intermediate principal stress on the mechanical and deformation characteristics of the Jiangxi undisturbed lateritic clay are analyzed by using the numerical simulations under the true tri-axial conditions. Results show that there exist significant influences of the intermediate principal stress effect factor on the soil deformation and failure and the pore water pressures. Under the consolidation undrained conditions, the shear strain decreases with the increase of intermediate principal stress effect factor in the case of the same shear stress, while the pore water pressure increases with the increase of intermediate principal stress effect factor in the case of the same axial strain. Under the consolidation drainage conditions, the bulk strain decreases with the increase of intermediate principal stress effect factor in the case of the same average normal stress, but increases with the increase of intermediate principal stress effect factor in the case of the same axial strain.
The triple-shear unified structured constitutive model is proposed for the undisturbed saturated clay in normal consolidation based on the disturbed state concept, in which the relative intact state is characterized by the non-linear elastic model, and the fully adjusted state is characterized by the elasto-plastic model built with the combination of the triple-shear failure criterion and the modified cam-clay model in the critical state soil mechanics. In order to describe the influences of the cohesion on the soil mechanical properties better, two treatments of the equivalent substitution and the coordinate translation are presented and are compared each other. The proposed model may overcome the shortcomings of the modified cam-clay model with the definite failure stress ratio without considering the soil cohesion, which can't reflect the practical differences of strength properties under different stress states and soil cohesion. The advantage is that the new model shows the practical effects under the different stress states acting on the saturated structured clay with different cohesion better. It features that it can describe the effects of intermediate principal stress, rang changes of stress and difference between tension and compression. Because the given structured constitutive model was built on the disturbed state concept and the critical state soil inmechanics is expressed as the stress-strain relations between the mean stress and the generalized shear stress and the bulk strain and the generalized shear strain, and there is no explicit formulation for the yielding function, a three-dimensionalized method is proposed for the previously given model. The three-dimensionalized structured constitutive model for the undisturbed clay may give relations among the six stress components and the six strain components under the complex stress or strain states, for which it is convenient to use in the practical geotechnical deformation analysis and in the finite element method coding. In order to verify the model proposed here, comparisons between the numerical simulations and experimental results under conventional tri-axial compression and K0 consolidation on the Jiangxi undisturbed lateritic clay are made and it shows that the proposed model could reflect the mechanical and deformation characteristics of the Jiangxi undisturbed lateritic clay well. Otherwise, the influences of the intermediate principal stress on the mechanical and deformation characteristics of the Jiangxi undisturbed lateritic clay are analyzed by using the numerical simulations under the true tri-axial conditions. Results show that there exist significant influences of the intermediate principal stress effect factor on the soil deformation and failure and the pore water pressures. Under the consolidation undrained conditions, the shear strain decreases with the increase of intermediate principal stress effect factor in the case of the same shear stress, while the pore water pressure increases with the increase of intermediate principal stress effect factor in the case of the same axial strain. Under the consolidation drainage conditions, the bulk strain decreases with the increase of intermediate principal stress effect factor in the case of the same average normal stress, but increases with the increase of intermediate principal stress effect factor in the case of the same axial strain.
引文
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[13]LIU M D,CARTER J P,DESAI C S,et al.Analysis of the compression of structured soils using the disturbed state concept[J].International journal for numerical and analytical methods in geomechanics,2015,24(8):723-735.
[14]DESAI C S,TOTH J.Disturbed state constitutive modeling based on stress-strain and nondestructive behavior[J].International journal of solids and structures,1996,33(11):1619-1650.
[15]DESAI C S.Constitutive modeling of materials and contacts using the disturbed state concept part 1-background and analysis[J].Computer and structures,2015,146:214-233.
[16]DESAI C S.Constitutive modeling of materials and contacts using the disturbed state concept part 2-validations at specimen and boundary value problem levels[J].Computer and structures,2015,146:234-251.
[17]WOOD D M.Soil behaviour and critical state soil mechanics[M].Cambridge:Soil Behaviour&Critical Soil Mechanics,1990.
[18]胡小荣,俞茂宏.岩土类介质强度准则新探[J].岩石力学与工程学报,2004,23(18):3037-3047.(HU Xiaorong,YU Maohong.New research on failure criterion for geomaterial[J].Chinese journal of rock mechanics and engineering,2004,23(18):3037-3047(in Chinese)).
[19]胡小荣,俞茂宏.材料三剪屈服准则研究[J].工程力学,2006,23(4):6-11.(HU Xiaorong,YU Maohong.Research on triple-shear yield criterion for materials[J].Engineering mechanics,2006,23(4):6-11(in Chinese)).
[2]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):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):1-6(in Chinese)).
[3]KATTI D R,DESAI C S.Modeling and testing of cohesive soil using the disturbed-state concept[J].Journal of engineering mechanics,1995,121(5):648-658.
[4]VARADARAJAN A,SHARMA K G,VENKATACHALAM K,et al.Testing and modeling two rock fill materials[J].Journal of engineering mechanics,2003,129(3):206-218.
[5]王常明,匡少华,王钢城,等.结构性土固结不排水剪特性的一种描述方法[J].岩土力学,2010,31(7):2035-2039.(WANGChangming,KUANG Shaohua,WANG Gangcheng,et al.A method for describing consolidated-undrained shear behavior of structured soil[J].Rock and soil mechanics,2010,31(7):2035-2039(in Chinese)).
[6]于亚磊.上海第(4)层粘土在不同应力路径下的力学特性实验与统一本构模拟[D].上海:上海交通大学,2015.(YU Yalei.Mechanical properties and constitutive modeling of Shanghai 4th clay under different stress path[D].Shanghai:Shanghai Jiao Tong University,2015(in Chinese)).
[7]CARTER J P,LIU M D.Review of the structured cam clay model[J].Geotechnical special publication,2005,128(128):99-132.
[8]DESAI C S,GENS A.Mechanics of materials and interfaces:the disturbed state concept[J].Journal of electronic packaging,2000,123(4):406.
[9]郑建业,葛修润,孙红.扰动状态理论在岩土力学问题中的应用[J].岩石力学与工程学报,2006,25(增刊2):3456-3462.(ZHENG Jianye,GE Xiurun,SUN Hong.Application of disturbed state concept to issues in geotechnical engineering[J].Chinese journal of rock mechanics and engineering,2006,25(S2):3456-3462(in Chinese)).
[10]邵帅,褚峰,邵生俊.Q3结构性黄土的扰动状态本构模型试验研究[J].岩石力学与工程学报,2016,35(7):1494-1500.(SHAO Shuai,CHU Feng,SHAO Shengjun.Experimental study on constitutive model of structural Q3 loess based on disturbed state concept[J].Chinese journal of rock mechanics and engineering,2016,35(7):1494-1500(in Chinese)).
[11]王国欣,肖树芳,黄宏伟,等.基于扰动状态概念的结构性粘土本构模型研究[J].固体力学学报,2004,25(2):191-197.(WANGGuoxin,XIAO Shufang,HUANG Hongwei,et al.Study of constitutive model of structural clay based on the disturbed state concept[J].Chinese journal of solid mechanics,2004,25(2):191-197(in Chinese)).
[12]LIU M D,CARTER J P.A structured Cam Clay model[J].Canadian geotechnical journal,2002,39(6):1313-1332.
[13]LIU M D,CARTER J P,DESAI C S,et al.Analysis of the compression of structured soils using the disturbed state concept[J].International journal for numerical and analytical methods in geomechanics,2015,24(8):723-735.
[14]DESAI C S,TOTH J.Disturbed state constitutive modeling based on stress-strain and nondestructive behavior[J].International journal of solids and structures,1996,33(11):1619-1650.
[15]DESAI C S.Constitutive modeling of materials and contacts using the disturbed state concept part 1-background and analysis[J].Computer and structures,2015,146:214-233.
[16]DESAI C S.Constitutive modeling of materials and contacts using the disturbed state concept part 2-validations at specimen and boundary value problem levels[J].Computer and structures,2015,146:234-251.
[17]WOOD D M.Soil behaviour and critical state soil mechanics[M].Cambridge:Soil Behaviour&Critical Soil Mechanics,1990.
[18]胡小荣,俞茂宏.岩土类介质强度准则新探[J].岩石力学与工程学报,2004,23(18):3037-3047.(HU Xiaorong,YU Maohong.New research on failure criterion for geomaterial[J].Chinese journal of rock mechanics and engineering,2004,23(18):3037-3047(in Chinese)).
[19]胡小荣,俞茂宏.材料三剪屈服准则研究[J].工程力学,2006,23(4):6-11.(HU Xiaorong,YU Maohong.Research on triple-shear yield criterion for materials[J].Engineering mechanics,2006,23(4):6-11(in Chinese)).
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