针对水泥改性淤泥质软土受冻融循环效应影响的工程问题,开展冻融循环处理后水泥土三轴剪切试验、CT扫描试验和SEM扫描试验,研究了不同冻融循环次数(0~10)次下水泥土的力学特征和微结构损伤规律。试验结果表明:水泥土三轴应力-应变曲线均为应变硬化曲线,黏聚力、内摩擦角随循环次数增加而逐渐减小,且分别表现为指数型和线性衰减趋势;根据CT扫描图像的二值化处理结果对裂隙演化规律进行了定量分析,发现裂隙率随循环次数增加保持指数型增加;在冻融循环过程中裂隙率与强度指标的变化保持一定的同步性;由SEM扫描试验可以观测到冻融循环使水泥土内部的水泥基胶结物流失,颗粒间密实度下降,这是导致裂隙扩展和力学性能衰减的微观机制。
Abstract
In the aim of understanding the changes of cement-reinforced silty soft soil under freeze-thaw cycles, we conducted triaxial compression tests, CT scanning, and SEM scanning on cement-soil specimens undergone 0-10 times of cyclic freezing and thawing to examine the mechanical properties and microstructural damage of soil specimens. Results revealed that the stress-strain curves of cement-soil displayed strain hardening features. With the increase of freeze-thaw cycles, the cohesion and internal friction angle shrank in exponential and linear trends, respectively. Binary results of CT scanning images manifested that the crack rate rose exponentially with the increase of freeze-thaw cycles. During cyclic freezing and thawing, the change of fracture rate synchronized with those of strength indicators. Moreover, from SEM scanning we observed losses of cementitious agents in the cement-soil and decay of compactness among particles, which led to the expansion of cracks and degradation of mechanical properties.
关键词
水泥土 /
冻融循环 /
三轴试验 /
裂隙特征 /
微观形态
Key words
cement-soil /
freeze-thaw cycles /
triaxial test /
fracture characteristic /
microstructure
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基金
江苏建筑节能与建造技术协同创新中心开放基金项目(SJXTQ1603);江苏省第五期“333工程”科研资助立项项目(BRA2018343)
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