Experimental study on strength properties of unsaturated intact loess in loess tableland regions
WANG Teng1, 2, ZHOU Ming-ru1, 2, WANG Jin-wei1, 2, CHEN Zhi-chao1, 2
1. Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China; 2. Key Laboratory of Disaoter Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou 730050, China
Abstract：In order to obtain the deformation and strength parameters and other related parameters of unsaturated intact loess in the loess tableland regions of Gansu Province, the triaxial consolidation drained shear tests are performed on the unsaturated intact loess with various initial suctions and net confining pressures. The deformation characteristics, critical state, strength parameters and suction variation characteristics of unsaturated intact loess are studied under the constant water content. The results show that the shear failure of intact loess belongs to plastic failure and exhibits significant shear contraction phenomenon. Under different initial suctions, the critical states of deviatoric stress and body strain are all linear. The strength envelope of undisturbed loess in p-q plane can be normalized to a straight line, and it can be expressed approximately with the critical state line of saturated soils. The shear strength of unsaturated loess is influenced by matrix suction, and the cohesion of unsaturated loess increases with the increase of the suction. The effective internal friction angle is less affected by the suction, which can be approximated as a constant. The strength parameters of unsaturated undisturbed loess in the loess tableland regions of Gansu Province are obtained. Besides, the parameter K has a great influence on the suction and there is a linear relationship between the parameter K and the suction.
王腾, 周茗如, 王晋伟, 陈志超. 黄土塬地区非饱和结构性黄土的强度特性研究[J]. 岩土工程学报, 2018, 40(S1): 189-197.
WANG Teng, ZHOU Ming-ru, WANG Jin-wei, CHEN Zhi-chao. Experimental study on strength properties of unsaturated intact loess in loess tableland regions. Chinese J. Geot. Eng., 2018, 40(S1): 189-197.
[1] 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)) [2] 李永乐, 张红芬, 佘小光, 等. 原状非饱和黄土的三轴试验研究[J]. 岩土力学, 2008, 29(10): 2859-2863. (LI Yong-le, ZHANG Hong-fang, SHI Xiao-guang, et al.Experimental study of triaxial test of undisturbed unsaturated loess[J]. Rock and Soil Mechanics, 2008, 29(10): 2859-2863. (in Chinese)) [3] DUNCAN J M, WONG K S, MARBY P.Stress-strain and bulk modulus parameters for finite element analysis of stresses and movement in soilmass[R]. Berkeley: University of Califomia, 1978. [4] 陈正汉. 重塑非饱和黄土的变形、强度、屈服和水量变化特性[J]. 岩土工程学报, 1999, 21(1): 82-90. (CHEN Zheng-han.Deformation, strength, yield and moismre change of a remolded unsaturated loess[J]. Chinese Journa of Geotechnical Engineering, 1999, 21(1): 82-90. (in Chinese)) [5] 陈正汉, 谢定义, 王永胜. 非饱和土的水气运动规律及其工程性质研究[J]. 岩土工程学报, 1993, 15(3): 53-56. (CHEN Zheng-han, XIE Ding-yi, WANG Yong-sheng.Experimental studies of laws of fluid motion, suction and pore pressures in unsaturated soil[J]. Chinese Journal of Geotechnical Engineering, 1993, 15(3): 53-56. (in Chinese)) [6] 陈存礼, 张登飞, 董玉柱, 等. 常含水率三轴条件下非饱和原状黄土的吸力和力学特性[J]. 岩土工程学报, 2014, 36(7): 1195-1202. (CHEN Cun-li, ZHANG Deng-feng, DONG Yu-zhu, et al.Suction and mechanical behaviours of unsaturated intact loess from constant water content triaxial tests[J]. Chinese Journal of Geotechnical Engineering, 2014, 36(7): 1195-1202. (in Chinese)) [7] 高帅,骆亚生,胡海军等. 非饱和原状黄土增湿条件下力学特性试验研究[J]. 岩土工程学报, 2015, 37(7): 1313-1318. (GAO Shuai, LUO Ya-sheng, HU Hai-jun,et al.Triaxial tests on water immersion of unsaturated and undisturbed loess[J]. Chinese Journal of Geotechnical Engineering, 2015, 37(7): 1313-1318. (in Chinese)) [8] 方祥位, 陈正汉, 申春妮, 等. 原状Q2黄土三轴剪切特性[J]. 岩石力学与工程学, 2008, 27(2): 383-389. (FANG Xiang-wei, CHEN Zheng-han, SHEN Chun-ni, et al.Triaxial shear properties of undisturbed loess Q2[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(2): 383-389. (in Chinese)) [9] 李加贵, 陈正汉, 黄雪峰. 原状Q3黄土湿陷特性的CT-三轴试验[J]. 岩石力学与工程学报, 2010, 29(6): 1288-1296. (LI Jia-gui, CHEN Zheng-han, HUANG Xue-feng.CT-triaxial test for collapse abllity of undisturbed Q3 loess[J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(6): 1288-1296. (in Chinese)) [10] BURLAND J B.Some aspects of the mechanical behavior of partly saturated soils[C]// Moisture Equilibria and Moisture Changes in the Soils Beneath Areas, A Symposium in Print, Butterworth, Sydney, 1965: 270-278. [11] DUNCAN J M, CHANG C Y.Nonliear analysis of stress and strain in soils[J]. SMFE ASCE, 1970, 96(SM5): 1629-1653. [12] 殷德顺, 王保田, 王云涛. 不同应力路径下的邓肯-张模型模量公式[J]. 岩土工程学报, 2007, 29(9): 1380-1385. (YIN De-shun, WANG Bao-tian, WANG Yun-tao.Tangent elastic modulus of Duncan-Chang model for different stress paths[J]. Chinese Journal of Geotechnical Engineering, 2007, 29(9): 1380-1385. (in Chinese)) [13] 殷宗泽, 周建, 赵仲辉, 等. 非饱和土本构关系及变形计算[J]. 岩土工程学报, 2006, 28(2): 137-146. (YIN Zong-ze, ZHOU Jian, ZHAO Zhong-hui, et al.Constitutive relations and deformation calculation for unsaturated soils[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(2): 137-146. (in Chinese)) [14] 王朝阳, 许强, 倪万魁, 等. 非饱和原状黄土的非线性损伤本构模型研究[J]. 岩土力学, 2010, 31(4): 1108-1111. (WANG Chao-yang, XU Qiang, NI Wan-kui, et al.Experimental study of triaxial test of undisturbed unsaturated loess[J].Rock and Soil Mechanics, 2010, 31(4): 1108-1111. (in Chinese)) [15] 王菁莪, 项伟, 毕仁能. 基质吸力对非饱和重塑黄土崩解性影响试验研究[J]. 岩土力学, 2011, 32(11): 3258-3262. (WANG Jing-e, XIANG Wei, BI Ren-neng.A nonlinear damage constitutive model of unsaturated undisturbed loess[J]. Rock and Soil Mechanics, 2011, 32(11): 3258-3262. (in Chinese)) [16] 冷艳秋. 饱和-非饱和重塑黄土变形强度特征[D]. 西安: 长安大学, 2014. (LENG Yan-qiu.The deformation and strength characteristics in saturated-unsaturated remodeled loess[D]. Xi'an: Chang'an University, 2014. (in Chinese)) [17] 马秀婷, 邵生俊, 杨春鸣, 等. 非饱和结构性黄土的强度特性试验研究[J]. 岩土工程学报, 2013, 35(增刊1): 68-75. (MA Xiu-ting, SHAO Sheng-jun, YANG Chun-ming, et al.Experimental research on the strength characteristic of unsaturated structural loess[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(S1): 68-75. (in Chinese)) [18] 申春妮, 方祥位, 王和文, 等. 吸力、含水率和干密度对重塑非饱和土抗剪强度影响研究[J]. 岩土力学, 2009, 30(5): 1347-1351. (SHEN Chun-ni, FANG Xiang-wei, WANG He-wen, et al.Research on effects of suction, water content and dry density on shear strength of remolded unsaturated soils[J]. Rock and Soil Mechanics, 2009, 30(5): 1347-1351. (in Chinese)) [19] 杨磊. 黄土抗剪强度特性分析[J]. 水利与建筑工程学报, 2010, 8(3): 163-165. (YANG Lei.Analysis of characteristics about shear strength of loess[J]. Journal of Water Resources and Architectural Engineering, 2010, 8(3): 163-165. (in Chinese)) [20] 党进谦, 李靖. 非饱和黄土的强度特征[J]. 岩土工程学报, 1997, 19(2): 56-61. (DANG Jin-qian, LI Jing.Strength characteristics of unsaturated loess[J]. Chinese Journal of Geotechnical Engineering, 1997, 19(2): 56-61. (in Chinese)) [21] FREDLUND D G, RAHARDIO H.Soil mechanics for unsaturated soils[M]. New York: John Wiley, 1993.
