Experimental study on influences of moisture content on shear strength of unsaturated loess
CAI Guo-qing1,2, ZHANG Ce2, HUANG Zhe-wen2, LI Jun-lin2, HOU Jian-long2
1. Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China; 2. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
Abstract：Determining the relationship between moisture content and shear strength is of guiding significance for engineering. The direct shear tests are carried out on the unsaturated loess samples with different moisture content and dry densities to study the shear strength of unsaturated loess, and the soil-water characteristic curve of unsaturated soil is determined by the method combining the dew point water potential meter and the filter paper method. Based on the researches on the microstructure of unsaturated soils, the influences of moisture content on the microstructure are analyzed. The test results show that as the moisture content increases, the shear strength of the soils decreases, and the increase in the moisture content reduces the cohesion of the soils and the internal friction angle, but has little effect on the internal friction angle. On this basis, the functional relationship between the moisture content and the shear strength index of unsaturated soils is analyzed, and then by analyzing the functional relationship between the moisture content in the soil-water characteristic curve and the matrix suction, a formula for the shear strength is proposed by regarding the matrix suction as the variable.
蔡国庆, 张策, 黄哲文, 李俊霖, 侯剑龙. 含水率对砂质Q3黄土抗剪强度影响的试验研究[J]. 岩土工程学报, 2020, 42(s2): 32-36.
CAI Guo-qing, ZHANG Ce, HUANG Zhe-wen, LI Jun-lin, HOU Jian-long. Experimental study on influences of moisture content on shear strength of unsaturated loess. Chinese J. Geot. Eng., 2020, 42(s2): 32-36.
[1] DONALD I B.Shear strength measurements in unsaturated non-cohe-sive soils with negative pore pressure[C]// Proceedings of the 2nd Australia and New Zealand Conference on Soil Mechanics and Foundation Engineering, 1956. [2] BISHOP A W, ALPAN I, BLIGHT G E, et al. Factors controlling the shear strength of partly saturated cohesive soil[C]// ASCE Res Conf Shear Strength of Cohesive Soils.1960, Boulder. [3] FREDLUND D G, MORGENSTERN N R, WILDGER R A.The shear strength of unsaturated soils[J]. Canadian Geotechnical Journal, 1978, 15(3): 313-321. [4] 党进谦, 李靖. 非饱和黄土的强度特征[J]. 岩土工程学报, 1997, 29(2): 59-64. (DANG Jing-qian, LI Jing.Strength characteristicsof unsaturated loess[J]. Chinese Journal of Geotechnical Engineering, 1997, 29(2): 59-64. (in Chinese)) [5] 姚攀峰. 再论非饱和土的抗剪强度[J].岩土力学, 2009, 30(8): 2315-2318. (YAO Pan-feng.Discussion on shear strength of unsaturated soils[J]. Rock and Soil Mechanics, 2009, 30(8): 2315-2318. (in Chinese)) [6] 凌华, 殷宗泽. 非饱和土强度随含水量的变化[J]. 岩石力学与工程学报, 2007(7): 1499-1503. (LING Hua, YIN Zong-ze.Variation of unsaturated soil strength with water contents[J]. Chinese Journal of Rock Mechanics and Engineering, 2007(7): 1499-1503. (in Chinese)) [7] 蔡国庆, 张策, 李舰, 等. 考虑初始干密度影响的SWCC预测方法研究[J]. 岩土工程学报, 2018, 40(增刊2): 27-31. (CAI Guo-qing, ZHANG Ce, LI Jian, et al.Study on prediction method of swcc considering initial dry density[J]. Chinese Journal of Geotechnical Engineering, 2018, 40(S2): 27-31. (in Chinese)) [8] FREDLUND D G, XING A Q.Equations for soil- watercharacteristic curve[J]. Canadian Geotechnical Journal, 1994, 31: 521-532. [9] 汪东林, 栾茂田, 杨庆. 重塑非饱和黏土的土-水特征曲线及其影响因素研究[J]. 岩土力学, 2009, 30(3): 751-756. (WANG Dong-lin, LUAN Mao-tian, YANG Qing.Experimental study of soil-water characteristic curve of remolded unsaturated clay[J]. Rock and Mechanics, 2009, 30(3): 751-756. (in Chinese))
