考虑卸荷速率的K_0固结膨胀土应力-应变行为
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摘要
通过GDS三轴试验系统对K_0固结原状南阳膨胀土原状样进行了不同卸荷速率和卸荷路径下的不排水三轴剪切试验,在试验资料的基础上,建立了K_0固结膨胀土的初始切线模量E_i和极限偏应力q_(ult)与固结应力及卸荷速率的关系式。发现,K_0固结膨胀土在卸荷剪切过程中的应力-应变关系曲线呈典型双曲线特征;膨胀土的不排水剪切强度随轴向固结应力及卸荷速率的增加而单调增加;E_i及q_(ult)随固结应力及卸荷速率的变化规律与强度基本类似,但E_i随固结应力的增加呈指数增加,而q_(ult)则表现为线性增加。通过改进邓肯-张双曲线表达式,建立了K_0固结膨胀土下不同卸荷速率时应力-应变关系的预测公式,并进行了模型验证。
A series of undrained triaxial shear tests on undisturbed Nanyang expansive clay under saturated K_0 condition have been performed. Two different stress paths, reduced triaxial compression(RTC) and reduced triaxial extension(RTE), four axial consolidation stress(80 k Pa, 160 kPa, 240 k Pa and 320 kPa), and three stress rate(0.02 kPa/min, 0.2 kPa/min and 2 kPa/min) were configured by GDS triaxial system. Based on the experimental data, the relationship among initial tangent modulus E_i, ultimate deviatoric stress q_(ult)of expansive soil, consolidation stress, and unloading rate was established. The results showed that the stress-strain relationship of expansive soil was hyperbolic along the unloading paths in both RTC test and RTE test. The shear strength increased as the stress rate and confined pressure increased monotonously. The changes of initial tangent modulus Ei and the ultimate principal stress difference q_(ult)were similar to the shear strength. The initial tangent modulus E_i increased exponentially and the ultimate principal stress difference q_(ult)increased linearly as the confined pressure increases. Based on the modified Duncan-Chang model, the prediction formula considering the stress rate was built for expansive soil under K_0 consolidation condition.
A series of undrained triaxial shear tests on undisturbed Nanyang expansive clay under saturated K_0 condition have been performed. Two different stress paths, reduced triaxial compression(RTC) and reduced triaxial extension(RTE), four axial consolidation stress(80 k Pa, 160 kPa, 240 k Pa and 320 kPa), and three stress rate(0.02 kPa/min, 0.2 kPa/min and 2 kPa/min) were configured by GDS triaxial system. Based on the experimental data, the relationship among initial tangent modulus E_i, ultimate deviatoric stress q_(ult)of expansive soil, consolidation stress, and unloading rate was established. The results showed that the stress-strain relationship of expansive soil was hyperbolic along the unloading paths in both RTC test and RTE test. The shear strength increased as the stress rate and confined pressure increased monotonously. The changes of initial tangent modulus Ei and the ultimate principal stress difference q_(ult)were similar to the shear strength. The initial tangent modulus E_i increased exponentially and the ultimate principal stress difference q_(ult)increased linearly as the confined pressure increases. Based on the modified Duncan-Chang model, the prediction formula considering the stress rate was built for expansive soil under K_0 consolidation condition.
引文
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[13]王大雁,马巍,常小晓,等.深部人工冻土在小应变条件下的刚度特性[J].岩土力学,2006,27(9):1447-1451.WANG Da-yan,MA Wei,CHANG Xiao-xiao,et al.Small-strain stiffness properties of frozen soils in deep alluvium[J].Rock and Soil Mechanics,2006,27(9):1447-1451.
[14]李新明.膨胀土超固结应力释放的力学性状与堑坡稳定性分析[J].武汉:中国科学院武汉岩土力学研究所,2013.LI Xin-ming.Mechanical behaviors of expansive soil due to the over-consolidated stress release and stability analysis of cut slope[D].Wuhan:Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,2013.
[15]YIN JIAN-HUA,ZHU JUN-GAO,GRAHAM JAMES.Anew elastic viscoplastic model for time-dependent behaviour of normally and overconsolidated clays:theory and verification[J].Canadian Geotechnical Journal,2002,39(1):157-173.
[16]NAKASE AKIO,KAMEI TAKESHI.Influence of strain rate on undrained shear characteristics of K0-consolidated cohesive soils[J].Soils and Foundations,1986,26(1):85-95.
[17]VAID Y P,CAMPANELLA R G.Time-dependent behavior of undisturbed clays[J].Journal of the Geotechnical Engineering Division,ASCE,1977,103(7):693-709.
[18]KONDNER R L.Hyperbolic stress-strain response:cohesive soils[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1963,89(SM1):115-143.
[2]陶太江,王志建,张家善.膨胀土的工程特性对开挖边坡稳定性的影响[J].安徽建筑工业学院学报(自然科学版),1994,2(2):15-22.TAO Tai-jiang,WANG Zhi-jian,ZHANG Jia-shan.Effect of engineering behavior of expansive soil to the stability of cut slope[J].Journal of Anhui Institute of Architecture(Natural Science),1994,2(2):15-22.
[3]刘祖德,孔官瑞.平面应变条件下膨胀土卸荷变形试验研究[J].岩土工程学报,1993,15(2):68-73.LIU Zu-de,KONG Guan-rui.Study on the unloading deformation behavior under plane strain condition of expansive soil[J].Chinese Journal of Geotechnical Engineering,1993,15(2):68-73.
[4]孔令伟,陈正汉.特殊土与边坡技术发展综述[J].土木工程学报,2012,45(5):141-161.KONG Ling-wei,CHEN Zheng-han.Advancement in the techniques for special soils and slopes[J].China Civil Engineering Journal,2012,45(5):141-161.
[5]李新明,孔令伟,郭爱国,等.考虑超固结比和卸荷速率影响的膨胀土卸荷力学特性研究[J].岩土力学,2013,34(增刊2):121-127.LI Xin-ming,KONG Ling-wei,GUO Ai-guo,et al.Effects of over consolidation ratio and stress rate on unloading mechanical behavior of expansive clay[J].Rock and Soil Mechanics,2013,34(Suppl.2):121-127.
[6]王钊,王俊奇,咸付生.万家寨引水隧洞成洞和运行的有限元分析[J].岩石力学与工程学报,2004,23(8):1257-1262.WANG Zhao,WANG Jun-qi,XIAN Fu-sheng.FEManalysis on tunneling and working of wanjiazhai water transmission tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(8):1257-1262.
[7]陈善雄,凌平平,何世秀,等.粉质黏土卸荷变形特性试验研究[J].岩土力学,2007,28(12):2534-2538.CHEN Shan-xiong,LING Ping-ping,HE Shi-xiu,et al.Experiamental study on deformation behavior of silty clay under unloading[J].Rock and Soil Mechanics,2007,28(12):2534-2538.
[8]李蓓,赵锡宏.软土的非线性弹性卸荷损伤模型[J].同济大学学报(自然科学版),2005,33(6):737-741.LI Bei,ZHAO Xi-hong.Non-linear elastic unloading damage model for soft soil[J].Journal of Tongji Unviersity(Natural Science),2005,33(6):737-741.
[9]HSIEH P G,OU C Y.Analysis of nonlinear stress and strain in clay under the undrained condition[J].Journal of Mechanics,2011,27(2):201-213.
[10]ALONSO E E.Modeling the mechanical behavior of expansive clays[J].Engineering Geology,1999,54:173-183.
[11]卢再华,陈正汉,方祥位,等.非饱和膨胀土的结构损伤模型及其在土坡多场耦合分析中的应用[J].应用数学和力学,2006,27(7):781-788.LU Zai-hua,CHEN Zheng-han,FANG Xiang-wei,et al.Structural damage model of unsaturated expansive soil and its application in multi-field couple analysis on expansive soil slope[J].Applied Mathematics and Mechanics,2006,27(7):781-788.
[12]张颖钧.超固结裂隙黏土堑坡首次滑动的简捷估算[J].铁道学报,1998,20(1):95-102.ZHANG Ying-jun.Simple estimation on initial sliding of a cut slope with over-consolidated fissured clay[J].Journal of China Railway Society,1998,20(1):95-102.
[13]王大雁,马巍,常小晓,等.深部人工冻土在小应变条件下的刚度特性[J].岩土力学,2006,27(9):1447-1451.WANG Da-yan,MA Wei,CHANG Xiao-xiao,et al.Small-strain stiffness properties of frozen soils in deep alluvium[J].Rock and Soil Mechanics,2006,27(9):1447-1451.
[14]李新明.膨胀土超固结应力释放的力学性状与堑坡稳定性分析[J].武汉:中国科学院武汉岩土力学研究所,2013.LI Xin-ming.Mechanical behaviors of expansive soil due to the over-consolidated stress release and stability analysis of cut slope[D].Wuhan:Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,2013.
[15]YIN JIAN-HUA,ZHU JUN-GAO,GRAHAM JAMES.Anew elastic viscoplastic model for time-dependent behaviour of normally and overconsolidated clays:theory and verification[J].Canadian Geotechnical Journal,2002,39(1):157-173.
[16]NAKASE AKIO,KAMEI TAKESHI.Influence of strain rate on undrained shear characteristics of K0-consolidated cohesive soils[J].Soils and Foundations,1986,26(1):85-95.
[17]VAID Y P,CAMPANELLA R G.Time-dependent behavior of undisturbed clays[J].Journal of the Geotechnical Engineering Division,ASCE,1977,103(7):693-709.
[18]KONDNER R L.Hyperbolic stress-strain response:cohesive soils[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1963,89(SM1):115-143.