Experimental study on air-dried shrinkage and frozen deformation characteristics of unsaturated bentonite
LIU Zhen-ya1, LIU Jian-kun1, LI Xu1, 2, FANG Jian-hong2
1. Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China; 2. Qinghai Research and Observation Base, Key Laboratory of Highway Construction & Maintenance Technology in Permafrost Regions, Ministry of Transport, Xining 810001, China;
Abstract：Saturated bentonite swells during freezing while unsaturated bentonite may shrink during freezing, which may be related to the water loss-induced shrinkage and ice-water phase transition-induced expansion. In order to investigate the contribution of these two parts, the bentonite samples with various void ratios and degrees of saturation are examined using the frozen deformation tests, air-dried shrinkage tests and freezing point tests. The test results demonstrate that the freezing point of the unsaturated bentonite mainly depends on its gravimetric water content and is much larger than that of unsaturated silt clay. The sample with high density becomes loose and the one with low density becomes dense after being frozen. The bentonite samples with low degree of saturation, i.e., 0.4, 0.5, 0.6, 0.7, shrink, whereas the sample with high degree of saturation (0.9) swells after being frozen. A linear relationship is found between the volumetric ice content and the ice-water phase transition-induced volumetric deformation, which is a comprehensive reflection of the influence of degree of saturation, void ratio and temperature on the deformation of unsaturated bentonite.
刘振亚, 刘建坤, 李旭, 房建宏. 非饱和膨润土失水收缩与冻结体变关系研究[J]. 岩土工程学报, 2018, 40(S1): 229-234.
LIU Zhen-ya, LIU Jian-kun, LI Xu, FANG Jian-hong. Experimental study on air-dried shrinkage and frozen deformation characteristics of unsaturated bentonite. Chinese J. Geot. Eng., 2018, 40(S1): 229-234.
[1] 秦冰, 陈正汉, 刘月妙, 等. 高庙子膨润土的胀缩变形特性及其影响因素研究[J]. 岩土工程学报, 2008(7): 1005-1010. (QIN Bing, CHEN Zheng-han, LIU Yue-miao, et al.Swelling-shrinkage behaviour of Gaomiaozi bentonite[J]. Chinese Journal of Geotechnical Engineering, 2008(7): 1005-1010. (in Chinese)) [2] 赖小玲, 叶为民, 刘毅, 等. 高庙子膨润土膨胀力时效性试验研究[J]. 岩土工程学报, 2014, 36(3): 574-579. (LAI Xiao-ling, YE Wei-min, LIU Yi, et al.Experimental investigation on ageing effects on swelling pressure of unsaturated GMZ01 bentonite[J]. Chinese Journal of Geotechnical Engineering, 2014, 36: 574-579. (in Chinese)) [3] KRAUS J F, BENSON C H, ERICKSON A E, et al.Freeze-thaw cycling and hydraulic conductivity of bentonitic barriers[J]. Journal of Geotechnical Engineering, 1997, 123(3): 229-238. [4] BARAST G, RAZAKAMANANTSOA A R, DJERAN- Maigre, et al.Swelling properties of natural and modified bentonites by rheological description[J]. Applied Clay Science, 2017, 142: 60-68. [5] 介玉新, 彭涛, 傅志斌, 等. 土工合成材料黏土衬垫的渗透性研究[J]. 土木工程学报, 2009(2): 92-97. (JIE Yu-xin, PENG Tao, FU Zhi-bin, et al.A study on the permeability of geosynthetic clay liners[J]. China Civil Engineering Journal, 2009(2): 92-97. (in Chinese)) [6] 霍凯成, 黄继业, 罗国荣. 路基冻胀机制及冻害防范整治措施探讨[J]. 岩石力学与工程学报, 2002, 21(7): 1099-1103. (HUO Kai-cheng, HUANG Ji-ye, LUO Guo-rong.On mechanism of freeze-heave and its treatment in roadbeds[J]. Chinese Journal of Geotechnical Engineering, 2002, 21(7): 1099-1103. (in Chinese)) [7] O'NEILL K, MILLER R D. Exploration of a rigid ice model of frost heave[J]. Water Resources Research, 1985, 21(3): 281-296. [8] 曾桂军, 张明义, 李振萍, 等. 饱和正冻土水分迁移及冻胀模型研究[J]. 岩土力学, 2015, 36(4): 1085-1092. (ZENG Gui-jun, ZHANG Ming-yi, LI Zhen-ping, et al.Study of moisture migration and frost heave model of freezing saturated soil[J]. Rock and Soil Mechanics, 2015, 36(4): 1085-1092. (in Chinese)) [9] 徐学祖, 王家澄, 张立新. 冻土物理学[M]. 北京: 科学出版社, 2001. (XU Xue-zu, WANG Jia-cheng, ZHANG Li-xin.Frozen soil physics[M]. Beijing: Science Press, 2001. (in Chinese)) [10] 周家作, 谭龙, 韦昌富, 等. 土的冻结温度与过冷温度试验研究[J]. 岩土力学, 2015, 36(3): 777-785. (ZHOU Jia-zuo, TAN Long, WEI Chang-fu, et al.Experimental research on freezing temperature and super-cooling temperature of soil[J]. Rock and Soil Mechanics, 2015, 36(3): 777-785. (in Chinese)) [11] American Society of Heating Refrigerating and Air- conditioning Engineers. Ashare handbook of fundamentals[S]. 2009. [12] 齐吉琳, 马巍. 冻融作用对超固结土强度的影响[J]. 岩土工程学报, 2006, 28(12): 2082-2086. (QI Ji-lin, MA Wei.Influence of freezing-thawing on strength of overconsolidated soils[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(12): 2082-2086. (in Chinese)) [13] BLACK P B, TICE A R.Comparison of soil freezing and soil water curve data for Windsor sandy loam[J]. Water Resources Research, 1989(25): 2205-2210. [14] AZMATCH T F, SEGO D C, ARENSON L U, et al. Using soil freezing characteristic curve to estimate the hydraulic conductivity function of partially frozen soils[J]. Cold Regions Science & Technology, 2012(S0): 83-84: 103-109. [15] 唐朝生, 崔玉军, TANG Anh-Minh, 等. 土体干燥过程中的体积收缩变形特征[J]. 岩土工程学报, 2011(8): 1271-1279. (TANG Chao-sheng, CUI Yu-jun, TANG Anh-Minh, et al.Volumetric shrinkage characteristics of soil during drying[J]. Chinese Journal of Geotechnical Engineering, 2011(8): 1271-1279. (in Chinese)) [16] 栾茂田, 汪东林, 杨庆, 等. 非饱和重塑土的干燥收缩试验研究[J]. 岩土工程学报, 2008, 30(1): 118-122. (LUAN Mao-tian, WANG Dong-lin, YANG Qing, et al.Experimental study on drying shrinkage of unsaturated compacted soils[J]. Chinese Journal of Geotechnical Engineering, 2008, 30(1): 118-122. (in Chinese)) [17] 徐学祖, 邓友生. 冻土中水分迁移的试验研究[M]北京: 科学出版社, 1991. (XU Xue-zu, DENG You-sheng.Experimental study on water migration in freezing and frozen soils[M]. Beijing: Science Press, 1991. (in Chinese))
