考虑结构性影响的原状黄土等效线性模型
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摘要
对不同含水率的西安原状黄土及相同干密度的扰动饱和黄土进行动三轴试验,用同一动应变下原状黄土的割线模量Edy与扰动饱和黄土的割线模量Edrs之比值定义了动三轴应力条件下结构性参数mεd,它可以综合反映土的排列和胶结特征所表现出的综合结构势(结构性强弱),探讨了动荷作用过程中不同固结围压及含水率下结构性参数变化特性。研究结果表明:①结构性参数可以反映含水率、固结围压对动三轴应力条件下原状黄土结构性的影响,具有很好的合理性、灵敏性、稳定性。用此结构性参数随含水率、固结围压的增大而减小的特性可以合理地解释原状黄土的动应力应变特性;②结构性参数的变化量mεd0?mεd与动应变εd关系可以用双曲线来拟合(mεd0为初始结构性参数),由此所得到的结构性参数表达式可以反映固结围压、湿度、密度、动应力和动应变对结构性的影响;③在扰动饱和土的等效线性模型中引入结构性参数所得到的原状黄土等效线性模型能够考虑增湿、加荷对原状黄土结构性的影响,计算结果与试验结果之间吻合较好。
Dynamic triaxial tests were conducted on Xi’an intact loess with different water contents and disturbed saturated loess with the same dry density as intact loess.A quantitative comprehensive structural parameter mε d was defined using ratio of secant modulus Edy of intact loess and secant modulus Edrs of disturbed saturated loess under dynamic triaxial stress condition,which could not only reflect arrangement but also coherent structure of soil particles.The effects of water content and consolidation confining pressure on the structural parameter were investigated under cyclic loading.It was indicated: ① The structural parameter could not only reveal the influences of water content and consolidation confining pressure on structure of intact loess under dynamic triaxial stress but also was rational and sensitiv as well as stable.The characteristics of dynamic stress strain could be rationally explained with that the structural parameter decerased with the increase of water content and consolidation confining pressure.② The relationship between quantitative variation of the structural parameter mεd0? mε and dynamic strainε d could be fitted with hyperbola(mε d0 was the initial structural parameter),and the equation of the structural parameter obtained could reveal the influence of consolidation confining pressure,water content,density,dynamic stress and dynamic strain on structure of the intact loess.③ A constitutive relation describing dynamic stress-strain behaviour of intact loess was presented by introducing the structural parameter to equivalent linear model of disturbed saturated loess,which could consider moistening and cyclic loading effect on structure of intact loess.Its rationality was confirmed by the agreement between the calculated and test results.
Dynamic triaxial tests were conducted on Xi’an intact loess with different water contents and disturbed saturated loess with the same dry density as intact loess.A quantitative comprehensive structural parameter mε d was defined using ratio of secant modulus Edy of intact loess and secant modulus Edrs of disturbed saturated loess under dynamic triaxial stress condition,which could not only reflect arrangement but also coherent structure of soil particles.The effects of water content and consolidation confining pressure on the structural parameter were investigated under cyclic loading.It was indicated: ① The structural parameter could not only reveal the influences of water content and consolidation confining pressure on structure of intact loess under dynamic triaxial stress but also was rational and sensitiv as well as stable.The characteristics of dynamic stress strain could be rationally explained with that the structural parameter decerased with the increase of water content and consolidation confining pressure.② The relationship between quantitative variation of the structural parameter mεd0? mε and dynamic strainε d could be fitted with hyperbola(mε d0 was the initial structural parameter),and the equation of the structural parameter obtained could reveal the influence of consolidation confining pressure,water content,density,dynamic stress and dynamic strain on structure of the intact loess.③ A constitutive relation describing dynamic stress-strain behaviour of intact loess was presented by introducing the structural parameter to equivalent linear model of disturbed saturated loess,which could consider moistening and cyclic loading effect on structure of intact loess.Its rationality was confirmed by the agreement between the calculated and test results.
引文
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[2]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 Ding-yi.Exploration of some new tendencies in research of loess soil mechanics[J].Chinese Journal of Geotechnical Engineering,2001,23(1):3–13.(in Chinese))
[3]谢定义,齐吉琳.土结构性及其定量化研究的新途径[J].岩土工程学报,1999,21(6):651–656.(XIE Ding-yi,QI Ji-lin.Soil structure characteristics and new approach in research on its quantitative parameter[J].Chinese Journal of Geotechnical Engineering,1999,21(6):651–656.(in Chinese))
[4]谢定义,齐吉琳,张振中.考虑土结构性的本构关系[J].土木工程学报,2000,33(4):35–40.(XIE Ding-yi,QI Ji-lin,ZHANG Zhen-zhong.A constitutive laws considering soil structural properties[J].China Civil Engineering Journal,2000,33(4):35–40.(in Chinese))
[5]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 Ding-yi,QI Ji-lin,ZHU Yuan-lin.Soil structure parameter and its relations to deformation and strength[J].Journal of Hydraulic Engineering,1999(10):1–6.(in Chinese))
[6]骆亚生,谢定义,邵生俊,等.非饱和黄土的结构变化特性[J].西北农林科技大学学报(自然科学版,)2004,8(8):114–118.(LUO Ya-sheng,XIE Ding-yi,SHAO Sheng-jun,ZHANG Ai-jun.Variation characteristics of soil structure of unsaturated loess[J].Journal of Northwest Sci-Tech Univ of Agri and For,(Natural Science Edition),2004,8(8):114–118.(in Chinese))
[7]骆亚生,谢定义.复杂应力条件下土的结构性本构关系[J].四川大学学报(工程科学版),2005,23(24):4248–4251.(LUO Ya-sheng,XIE Ding-yi.Structural constitutive relation of soils under complex stress conditions[J].Journal of Sichuan University(Engineering Science Edition),2004,23(24):4248–4251.(in Chinese))
[8]陈存礼,胡再强,高鹏.原状黄土的结构性及其与变形特性关系研究[J].岩土力学,2006,27(11):1891–1896.(CHEN Cun-li,HU Zai-qiang,GAO Peng.Research on relationship between structure and deformation property of intact loess[J].Rock and Soil Mechanics,2006,27(11):1891–1896.(in Chinese))
[9]陈存礼,胡再强,谢定义.赤泥的变形-强度特性与结构性关系的研究[J].岩土力学,2004,25(12):1862–1866.(CHEN Cun-li,HU Zai-qiang,XIE Ding-yi.Research on the relationship between deformation–strength property and structure of red mud[J].Rock and Soil Mechanics,2004,25(12):1862–1866.(in Chinese))
[10]陈存礼,高鹏,胡再强.黄土的增湿变形特性及其与结构性的关系[J].岩石力学与工程学报,2006,25(7):1352–1360.(CHEN Cun-li,GAO Peng,HU Zai-qiang.Moistening deformation characteristic of loess and its relation to structure[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(7):1352–1360.(in Chinese))
[11]骆亚生,谢定义,邵生俊,张爱军.复杂应力条件下的土结构性参数[J].岩石力学与工程学报,2004,23(24):4248–4251.(LUO Ya-sheng,XIE Ding-yi,SHAO Sheng-jun,ZHANG Ai-jun.Structural parameter of soil under complex stress conditions[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(24):4248–4251.(in Chinese))
[12]王兰民.黄土动力学[M].北京:地震出版社,2003.(WANG Lan-min.Loess dynamics[M].Beijing:Earthquake Press,2003.(in Chinese))
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