冻融循环下纳米黏土改性滨海水泥土的微观结构

为探究冻融循环下纳米黏土对滨海水泥土微观结构的改性效果,通过扫描电子显微镜微观测试对土体微观结构变化规律进行分析,探讨了土体的微观结构定量化参数与宏观力学特征的关联性.以纳米滨海水泥土为对象,利用扫描电子显微镜和Image Pro Plus软件获取土体在0、1、5、7、9、11次的冻融循环下的微观结构特征和量化参数.结果表明:①在未冻融的环境下,纳米黏土改善滨海水泥土微观结构效果明显,孔隙明显减小.②在冻融环境下,纳米黏土在冻融循环初期对滨海水泥土微观结构的改性效果好,表现在冻融循环0～5次内孔隙面积平均减少14.3％,而冻融循环7～11次时仅平均减少4.3％的孔隙面积.通过概率密度函数的分布可知纳米黏土抑制了滨海水泥土超大孔隙的发育.③纳米滨海水泥土的压缩系数对颗粒面积变化比较敏感,颗粒的数量、不均匀系数等微观结构参数对压缩系数的影响较小.

Microstructure of Coastal Soil Modified with Cement and Nano-clay Soil Under Freeze-thaw Cycles

The improvement effect of modified coastal cement soil by nano-clay under freeze-thaw cycles was evaluated from the view of soil microstructure. The change law of soil microstructure was analyzed by SEM micro test, and the correlation between the quantification of soil microstructure and macro-mechanical characteristics was explored. The microstructure characteristics and quantitative parameters of coastal cement soil and nano coastal cement soil under freezing and thawing cycles of 0,1,5,7,9 and 11 were obtained by scanning electron microscope and Image Pro Plus software. The results show that:(1) Under the condition of no freeze-thaw cycle, the effect of nano-clay on improving coastal cement soil is obvious. (2) In freeze-thaw environment, the effect of nano-clay on coastal cement is good at the early stage of freeze-thaw cycle, but the effect decreases with the increase of freeze-thaw cycles. In 0-5 cycles of freeze-thaw cycles, the pore area of nano coastal cement soil decreased by 14.3% on average. While in 7-11 cycles of freeze-thaw cycles, the pore area decreased by 4.3% on average. According to the distribution of the probability density function, the nano-clay inhibited the development of the super-macropores in coastal cement soil. (3) The compressibility of nano-sized soil is sensitive to the change of particle area, and the number of particles and the coefficient of inhomogeneity have little effect on the compressibility. The results indicate that the nano-clay can improve effectively the freeze-thaw resistance of the coastal cement soil in a short time.