Microcosmic pore characteristics evolution of the cement improved frozen soil after thawing compression
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摘要:
水泥改良冻土在融化压缩下的微观孔隙演变特征研究，对了解水泥改良冻土的过程具有重要意义。将水泥改良后的冻土进行融化压缩实验，通过冷冻干燥法对试验后的土样进行电镜样品制取并获取其微观特征图像。对试验土样进行比重测试，得到土样真实的三维孔隙比。最后以真实孔隙比作参考，确定图像分割所选取的灰度值并提取其孔隙特征。结合融化压缩试验结果，对水泥改良冻土的孔隙数量、面积、定向角及丰度值随改良土压缩量的变化关系进行了分析。研究结果表明：经过水泥改良后的冻土，大孔隙结构强度增大明显；随着水泥掺量及养护龄期的增加，孔隙比与孔隙面积变大，压缩量变小；随着土体压缩量的增大，孔隙的定向角分布逐渐由均匀状向锯齿状发展；土样压缩过程中，丰度值大于0.5的孔隙发生压缩明显，孔隙逐渐趋于细长状，并且随着压缩量的增大，孔隙丰度值的分布越来越趋于正态分布。孔隙微观结构演变研究为阐释水泥改良冻土宏观力学特性增强的机制提供了科学依据。
Abstract:The research on microcosmic characteristics evolution of the cement improved frozen soil under thawing compression is of great significance to understand the process of the improvement. In this study, Thawing compression test is conducted with the cement treated frozen soil. The specimens of SEM are prepared with the method of freezing- drying and the microscopic characteristic images are obtained. The real three-dimensional pore ratio is obtained by the specific gravity test. The gray value is selected for image segmentation as the reference of the real pore ratio and the microscopic pore characteristic is extracted. Based on the results of the compression test, the pore characteristics, such as the diameter, quantity, area, directional angle and abundance, are quantitatively analyzed. The results show that the strength of macropore structures is enhanced when the frozen soil is improved by cement, causing an increasing pore ratio and pore area, and a decreasing compression. With the development of the compression, the orientation angle distribution of the pores transfers from the originally uniform style to the serrated style. The pores tend to be elongated with the compaction of the pores with the abundance value greater than 0.5 while the whole pore abundances tend gradually to be normal distribution. The research on microstructure evolution provides a scientific basis for interpreting the mechanism of the enhancement on the macroscopic mechanical properties of the cement improved frozen soil.
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表 1 不同水泥土的比重结果
Table 1. Different soil-cement specific gravity results
掺量/% SAC OPC 3 d 28 d 3 d 28 d 5 2.935 3.016 2.988 3.013 10 2.948 3.027 3.017 3.025 15 2.954 3.034 3.034 3.033 
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