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摘要: 为研究主应力方向和大小耦合变化对土体应力-应变状态及非共轴性的影响, 采用空心圆柱扭剪仪对饱和重塑黄土开展一系列循环扭剪试验, 分析了应力-应变状态和非共轴角的变化规律及影响因素。试验结果表明: 轴向应变始终处于压缩状态, 环向应变先负向累积再正向累积, 径向应变基本处于受拉状态, 剪切应变的受拉与受压状态交替出现, 轴向、环向和剪切应变曲线的波动特性明显, 而径向应变曲线的波动特性弱, 说明循环荷载作用下各应变分量表现出不同的发展规律; 轴向和径向应变及环向和剪切应变变化幅值随中主应力系数的增大先增大后减小, 说明中主应力系数影响各应变分量的累积; 随着主应力方向角旋转范围的增大, 轴向和径向应变逐渐减小, 环向应变由负向往正向变化的趋势提前, 剪切应变变化幅值逐渐减小, 说明主应力方向角旋转范围影响各应变分量的发展趋势; 剪切和正偏应力-应变曲线滞回现象明显, 且刚度发生循环强化, 但剪切刚度的循环强化比正偏刚度更明显, 说明土体出现次生各向异性, 这是引起非共轴现象的内在因素; 非共轴角变化曲线随中主应力系数的增大先下移后上移, 随循环次数的增大而逐渐上移, 随偏应力幅值的增大其变化范围增大。可见, 循环荷载下中主应力系数、循环次数和偏应力幅值可显著影响饱和重塑黄土的应力-应变状态及非共轴性, 在黄土工程设计和本构关系研究中应加以考虑。Abstract: To study the effect of coupling changes in principal stress direction and magnitude on the stress-strain state and non-coaxiality of soil, a series of cyclic torsional shear tests were carried out on the saturated remolded loess by using a hollow cylindrical torsional shear apparatus, and the variation rules and influencing factors of stress-strain state and non-coaxial angle were analyzed. Experimental result shows that the axial strain is always in a compression state, the hoop strain accumulates negatively first and then positively, the radial strain is basically in a tension state, the tension and compression states of shear strain alternate, the fluctuation characteristics of axial, hoop and shear strain curves are obvious, while the fluctuation characteristic of radial strain curve is weak, indicating that each strain component shows different development laws under the cyclic loading. The axial and radial strains and the variation amplitudes of hoop and shear strains increase first and then decrease as the intermediate principal stress coefficient increases, indicating that the intermediate principal stress coefficient affects the cumulation of each strain component. With the increase of rotation range of principal stress direction angle, the axial and radial strains decrease gradually, the trend of hoop strain changing from negative to positive advances, and the variation amplitude of shear strain decreases gradually, indicating that the rotation range of principal stress direction angle affects the development trend of each strain component. The hysteresis phenomena of shear and normal differential stress-strain curves are obvious, and the stiffness consolidates cyclically, but the cyclic strengthening of shear stiffness is more obvious than that of normal differential stiffness, indicating that the secondary anisotropy occurs in the soil. This is an intrinsic cause of the non-coaxial phenomenon. The non-coaxial angle curve moves down first and then moves up as the intermediate principal stress coefficient increases, and moves up gradually as the cycle number increases. The variation range of non-coaxial angle curve increases as the deviating stress amplitude increases. Thus, the intermediate principal stress coefficient, cycle number and deviating stress amplitude can obviously affect the stress-strain state and non-coaxiality of saturated remolded loess, which should be considered in loess engineering design and constitutive relationship research.
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表 1 试验方案
Table 1. Test programme
试样编号 p3/kPa b q/kPa α/ (°) A 250 1.0 20 -45~45 B 250 1.0 20 -60~60 C1 250 0.0 20 -75~75 C2 250 0.5 20 -75~75 C3 250 1.0 20 -75~75 C4 250 0.0 10 -75~75 C5 250 0.0 30 -75~75 -
[1] YU H S, YUAN X. On a class of non-coaxial plasticity models for granular soils[J]. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2006, 462: 725-748. doi: 10.1098/rspa.2005.1590 [2] YANG Y M, YU H S. Numerical simulations of simple shear with non-coaxial soil models[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2006, 30: 1-19. doi: 10.1002/nag.468 [3] YANG Y, YU H S. Application of a non-coaxial soil model in shallow foundation[J]. Geomechanics and Geoengineering, 2006, 1 (2): 139-150. doi: 10.1080/17486020600777101 [4] ZHOU Jian, YAN Jia-jia, LIU Zheng-yi, et al. Undrained anisotropy and non-coaxial behavior of clayey soil under principal stress rotation[J]. Journal of Zhejiang University—Science A (Applied Physics and Engineering), 2014, 15 (4): 241-254. doi: 10.1631/jzus.A1300277 [5] 钱建固, 王永刚, 张甲锋, 等. 交通动载下饱和软黏土累计变形的不排水循环扭剪试验[J]. 岩土工程学报, 2013, 35 (10): 1790-1798. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310005.htmQIAN Jian-gu, WANG Yong-gang, ZHANG Jia-feng, et al. Undrained cyclic torsion shear tests on permanent deformation responses of soft saturated clay to traffic loadings[J]. Chinese Journal of Geotechnical Engineering, 2013, 35 (10): 1790-1798. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201310005.htm [6] 郭莹, 栾茂田, 何杨, 等. 主应力方向循环变化对饱和松砂不排水动力特性的影响[J]. 岩土工程学报, 2005, 27 (4): 403-409. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC200504007.htmGUO Ying, LUAN Mao-tian, HE Yang, et al. Effect of variation of principal stress orientation during cyclic loading on undrained dynamic behavior of saturated loose sands[J]. Chinese Journal of Geotechnical Engineering, 2005, 27 (4): 403-409. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC200504007.htm [7] 肖军华, 许世芹, 韦凯, 等. 主应力轴旋转对地铁荷载作用下软黏土累积变形的影响[J]. 岩土力学, 2013, 34 (10): 2938-2945. https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201310028.htmXIAO Jun-hua, XU Shi-qin, WEI Kai, et al. Influences of rotation of principal stress axis on accumulative deformation of soft clay under subway cyclic loading[J]. Rock and Soil Mechanics, 2013, 34 (10): 2938-2945. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201310028.htm [8] 郭林, 蔡袁强, 王军, 等. 长期循环荷载作用下温州结构性软黏土的应变特性研究[J]. 岩土工程学报, 2012, 34 (12): 2249-2254. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201212017.htmGUO Lin, CAI Yuan-qiang, WANG Jun, et al. Long-term cyclic strain behavior of Wenzhou structural soft clay[J]. Chinese Journal of Geotechnical Engineering, 2012, 34 (12): 2249-2254. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201212017.htm [9] WANG Y K, GAO Y F, ZENG C N, et al. Undrained cyclic behavior of soft marine clay involved combined principal stress rotation[J]. Applied Ocean Research, 2018, 81: 141-149. doi: 10.1016/j.apor.2018.10.010 [10] 蔡燕燕, 俞缙, 余海岁, 等. 考虑主应力轴旋转的砂土变形特性试验研究[J]. 岩石力学与工程学报, 2013, 32 (2): 417-424. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX201302024.htmCAI Yan-yan, YU Jin, YU Hai-sui, et al. Experimental study of deformation behaviour of sand under rotation of principal stress axes[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32 (2): 417-424. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX201302024.htm [11] NAKATA Y, HYODO M, MURATA H, et al. Flow deformation of sands subjected to principal stress rotation[J]. Soils and Foundations, 1998, 38 (2): 115-128. doi: 10.3208/sandf.38.2_115 [12] 沈扬. 考虑主应力方向变化的原状软黏土试验研究[D]. 杭州: 浙江大学, 2007.SHEN Yang. Experimental study on effect of variation of principal stress orientation on undisturbed soft clay[D]. Hangzhou: Zhejiang University, 2007. (in Chinese). [13] 严佳佳, 周建, 刘正义, 等. 主应力轴纯旋转条件下黏土弹塑性变形特性[J]. 岩石力学与工程学报, 2014, 33 (增2): 4350-4358. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2014S2121.htmYAN Jia-jia, ZHOU Jian, LIU Zheng-yi, et al. Elasto-plastic deformation behavior of intact clay subjected to principal stress rotation[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33 (S2): 4350-4358. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2014S2121.htm [14] 周建, 郑鸿镔, 温晓贵, 等. 考虑中主应力系数影响的主应力轴旋转下原状软黏土变形研究[J]. 浙江大学学报(工学版), 2011, 45 (12): 2134-2141. https://www.cnki.com.cn/Article/CJFDTOTAL-ZDZC201112012.htmZHOU Jian, ZHENG Hong-bin, WEN Xiao-gui, et al. Deformation of intact soft clay under principal stress rotation with effect of intermediate principal stress[J]. Journal of Zhejiang University (Engineering Science), 2011, 45 (12): 2134-2141. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZDZC201112012.htm [15] 杨彦豪, 周建, 周红星. 主应力轴旋转条件下软黏土的非共轴研究[J]. 岩石力学与工程学报, 2015, 34 (6): 1259-1266. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX201506021.htmYANG Yan-hao, ZHOU Jian, ZHOU Hong-xing. Non-coaxial behaviour of soft clay subjected to principal stress rotation[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34 (6): 1259-1266. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX201506021.htm [16] 翁效林, 赵彦虎, 张玉伟, 等. 主应力轴旋转条件下黄土变形特性试验[J]. 中国公路学报, 2018, 31 (5): 9-16. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201805003.htmWENG Xiao-lin, ZHAO Yan-hu, ZHANG Yu-wei, et al. Experimental study on deformation characteristics of loess under condition of principal stress axes rotation[J]. China Journal of Highway and Transport, 2018, 31 (5): 9-16. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201805003.htm [17] 肖杰, 杨和平, 林京松, 等. 模拟干湿循环及含低围压条件的膨胀土三轴试验[J]. 中国公路学报, 2019, 32 (1): 21-28. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201901004.htmXIAO Jie, YANG He-ping, LIN Jing-song, et al. Simulating wet-dry cycles and low confining pressures triaxial test on expansive soil[J]. China Journal of Highway and Transport, 2019, 32 (1): 21-28. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201901004.htm [18] DRESCHER A, DE JONG G D J. Photoelastic verification of a mechanical model for the flow of a granular material[J]. Journal of the Mechanics and Physics of Solids, 1972, 20 (5): 337-340. [19] GUTIERREZ M, ISHIHARA K. Non-coaxiality and energy dissipation in granular material[J]. Soils and Foundations, 2000, 40 (2): 49-59. [20] TONG Zhao-xia, ZHANG Jian-min, YU Yi-lin, et al. Drained deformation behavior of anisotropic sands during cyclic rotation of principal stress axes[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2010, 136 (11): 1509-1518. [21] MIURA K, MIURA S, TOKI S. Deformation behavior of anisotropic dense sand under principal stress axes rotation[J]. Soils and Foundations, 1986, 26 (1): 36-52. [22] 扈萍, 魏超, 杨令强, 等. 主应力轴往复循环旋转下砂土的变形特性研究[J]. 地下空间与工程学报, 2018, 14 (4): 955-961. https://www.cnki.com.cn/Article/CJFDTOTAL-BASE201804011.htmHU Ping, WEI Chao, YANG Ling-qiang, et al. Deformation behavior of sands under reciprocating cyclic principal stress rotation[J]. Chinese Journal of Underground Space and Engineering, 2018, 14 (4): 955-961. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-BASE201804011.htm [23] XIAO J H, JUANG C H, WEI K, et al. Effects of principal stress rotation on the cumulative deformation of normally consolidated soft clay under subway traffic loading[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2014, 140 (4): 04013046-1-9. [24] WANG Yu-ke, GAO Yu-feng, GUO Lin. Influence of intermediate principal stress and principal stress direction on drained behavior of natural soft clay[J]. International Journal of Geomechanics, 2018, 18 (1): 04017128-1-15. [25] 刘家顺, 王来贵, 张向东, 等. K0固结粉质黏土非共轴特性试验研究[J]. 岩石力学与工程学报, 2017, 36 (增2): 4205-4211. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2017S2054.htmLIU Jia-shun, WANG Lai-gui, ZHANG Xiang-dong, et al. Experimental study on non-coaxial characteristics of K0 consolidation saturated silty clay[J]. Chinese Journal of Rock Mechanics and Engineering, 2017, 36 (S2): 4205-4211. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2017S2054.htm [26] 沈扬, 徐海东, 王保光, 等. 列车荷载引起心形应力路径下软土非共轴应变特征研究[J]. 岩土力学, 2017, 38 (1): 1-9. https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201701001.htmSHEN Yang, XU Hai-dong, WANG Bao-guang, et al. Strain characteristics of non-coaxiality under heart-shaped stress path caused by train loads in soft clay[J]. Rock and Soil Mechanics, 2017, 38 (1): 1-9. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201701001.htm [27] 伍婷玉, 郭林, 蔡袁强, 等. 交通荷载应力路径下K0固结软黏土变形特性试验研究[J]. 岩土工程学报, 2017, 39 (5): 859-867. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201705013.htmWU Ting-yu, GUO Lin, CAI Yuan-qiang, et al. Deformation behavior of K0-consolidated soft clay under traffic load-induced stress paths[J]. Chinese Journal of Geotechnical Engineering, 2017, 39 (5): 859-867. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201705013.htm [28] 尚许雯. 循环荷载下黄土的应力特性与非共轴效应试验研究[D]. 西安: 长安大学, 2018.SHANG Xu-wen. The stress characteristics and non-coaxiality of loess in cyclic loading test[D]. Xi'an: Chang'an University, 2017. (in Chinese). [29] 童朝霞. 应力主轴循环旋转条件下砂土的变形规律与本构模型研究[D]. 北京: 清华大学, 2008.TONG Zhao-xia. Research on deformation behavior and constitutive model of sands under cyclic rotation of principal stress axes[D]. Beijing: Tsinghua University, 2008. (in Chinese). [30] 钱建固, 杜子博. 纯主应力轴旋转下饱和软黏土的循环弱化及非共轴性[J]. 岩土工程学报, 2016, 38 (8): 1381-1390. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201608004.htmQIAN Jian-gu, DU Zi-bo. Cyclic degradation and non-coaxiality of saturated soft clay subjected to pure rotation of principal stress axis[J]. Chinese Journal of Geotechnical Engineering, 2016, 38 (8): 1381-1390. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201608004.htm [31] GUTIERREZ M, ISHIHARA K, TOWHATA I. Flow theory for sand during rotation of principal stress direction[J]. Soils and Foundations, 1991, 31 (4): 121-132. [32] DESRUES J, CHAMBON R. Shear band analysis and shear moduli calibration[J]. International Journal of Solids and Structures, 2002, 39 (13/14): 3757-3776.