Triaxial drainage shear tests are conducted on undisturbed and remolded samples of marshy and lacustrine clay to explore the mechanism of structure affecting shear strength and deformation. The undisturbed soil samples after the triaxial drainage shear test are photographed by scanning electron microscope (SEM) and the SEM photos are qualitatively and quantitatively analyzed by IPP program. In addition, the effects of soil structure on shear strength and deformation and the change of microstructure of marshy and lacustrine clay are examined under different consolidation pressures. Results demonstrate that before the yield failure of soil structure, the soil structure of the undisturbed soil could enhance shear strength and reduce shear deformation, while after the yield failure of soil structure, the soil structure of undisturbed soil reduces shear strength and instigates shear deformation which is similar to the remolded soil. Moreover, the peak structural strength of undisturbed soil increases linearly and the peak structural volumetric strain decreases exponentially with the growth of confining pressure. When consolidation pressure is smaller than structural yield stress, the soil structure damages slightly in consolidation stage, and the shear load is bore by the bonding and fabric of the undisturbed soil in shearing stage. Meanwhile, the pores are almost uncompressed and the shape and arrangement of particles and pores have changed slightly. However, when consolidation pressure exceeds the structural yield stress, the soil structure damages significantly in consolidation stage and the bonding and fabric gradually degrades in shearing stage. As a result, the pores are compressed, the shape of particles and pores gradually becomes circular, and the arrangement orientation of particles and pores adjust with the direction of load.
Key words
marshy and lacustrine clay /
triaxial drained shear test /
soil structure /
microstructure /
undisturbed soil /
remoulded soil
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
References
[1] 刘春原, 王向会. 衡水湖湿地湖泊相软土研究[M]. 北京: 人民交通出版社, 2016.
[2] 龚晓南, 熊传祥, 项可祥, 等. 粘土结构性对其力学性质的影响及形成原因分析[J]. 水利学报, 2000 (10): 43-47.
[3] 胡瑞林. 粘性土微结构定量模型及其工程地质特征研究[M]. 北京: 地质出版社, 1995.
[4] BURLAND J B. On the Compressibility and Shear Strength of Natural Clays[J]. Géotechnique, 1990, 40(3): 329-378.
[5] CALLISTO L, CALABRESI G. Mechanical Behaviour of a Natural Soft Clay[J]. Géotechnique, 1998, 48(4): 495-513.
[6] HONG Z S, LIU S Y, SHEN S Y, et al. Comparison in Undrained Shear Strength between Undisturbed and Remolded Ariake Clays[J]. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 2006, 132(2): 272-275.
[7] HONG Z S, ZHENG L L, CUI Y J, et al. Compression Behaviour of Natural and Reconstituted Clays[J]. Géotechnique, 2012, 62(4): 291-301.
[8] 王国欣, 肖树芳, 黄宏伟. 杭州海积软土应力–应变特征与结构强度损伤规律研究[J]. 岩石力学与工程学报, 2005, 24(9): 1555-1560.
[9] 张 宏, 柳艳华, 杜东菊. 基于孔隙特征的天津滨海软粘土微观结构研究[J]. 同济大学学报(自然科学版), 2010, 38(10): 1444-1449.
[10]陈晓平. 海陆交互相沉积软土固结效应[J]. 岩土工程学报, 2011, 33(4): 520-528.
[11]张先伟, 孔令伟, 郭爱国, 等. 不同固结压力下强结构性黏土孔隙分布试验研究[J]. 岩土力学, 2014, 35(10): 2794-2800.
[12]周 建, 邓以亮, 曹 洋, 等. 杭州饱和软土固结过程微观结构试验研究[J]. 中南大学学报(自然科学版), 2014, 45(6): 1998-2005.
[13]龙 凡, 王立忠, 李 凯, 等. 舟山黏土和温州黏土灵敏度差别成因[J]. 浙江大学学报(工学版), 2015, 49(2): 218-224.
[14]陈 波, 孙德安, 高 游, 等. 弱胶结结构性软黏土力学特性的试验研究[J]. 岩土工程学报, 2017, 39(12): 2296-2303.
[15]刘勇健, 李彰明, 郭凌峰, 等. 基于核磁共振技术的软土三轴剪切微观孔隙特征研究[J]. 岩石力学与工程学报, 2018, 37(8): 1924-1932.
[16]朱 楠, 刘春原, 赵献辉, 等. 湿地湖泊相黏土一维固结压缩特性宏微观试验研究[J]. 长江科学院院报, 2020,37(2): 93-99.
[17]朱 楠, 刘春原, 赵献辉, 等. 结构性对湿地湖泊相软土不排水剪切强度特性的影响[J]. 硅酸盐通报, 2019, 38(3): 858-864,871.
[18]GB/T 50123—1999,土工试验方法标准[S]. 北京: 中国计划出版社, 1999.
[19]张季如, 祝 杰, 黄 丽, 等. 土壤微观结构定量分析的IPP图像技术研究[J]. 武汉理工大学学报, 2008, 30(4): 80-83.
[20]张先伟, 王常明. 一维压缩蠕变前后软土的微观结构变化[J]. 岩土工程学报, 2010, 32(11): 1688-1694.
[21]施 斌. 粘性土击实过程中微观结构的定量评价[J]. 岩土工程学报, 1996, 18(4): 57-62.
PDF(6862 KB)
