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基于不同分形模型的冻融黄土孔隙特征研究

陈  鑫1,2,张  泽1,李东庆1   

  1. 1.中国科学院 西北生态环境资源研究院 冻土工程国家重点实验室; 2.中国科学院大学
  • 收稿日期:2018-08-07 修回日期:2018-10-21 出版日期:2019-07-23 发布日期:2019-07-23
  • 通讯作者: 张泽
  • 基金资助:
    冷生土壤粉质化过程中的物质重组特征及其沉积环境意义;耦合多源数据的兴贝型多年冻土时空变化研;冻土工程国家重点实验室自主研究项目

Study on pore characteristics of freezing-thawing loess based on different fractal models

CHEN Xin1, 2, ZHANG Ze1, LI Dongqing1   

  1. 1. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences;
    2. University of Chinese Academy of Sciences
  • Received:2018-08-07 Revised:2018-10-21 Online:2019-07-23 Published:2019-07-23
  • Contact: ZHANG Ze

摘要: 为了得到冻融作用对黄土孔径分布的影响规律,以重塑黄土为研究对象,利用压汞法测试经历不同冻融循环次数后黄土样品的孔隙特征,采用3种分形模型对冻融作用后的黄土微观孔隙结构进行定量表征和对比研究。结果表明:未经冻融作用的黄土孔隙分布曲线呈单峰分布,经历冻融作用的黄土孔隙分布曲线呈双峰甚至多峰分布。冻融作用对黄土中孔径分布在0.1~10?m范围内的孔隙影响较大。前10次冻融作用使黄土孔隙率增加,特别是经历6次冻融作用后,与未经历冻融作用的黄土相比孔隙率增大约18.8%。随着冻融作用的继续,黄土孔隙率减小且趋于稳定。经历不同冻融循环次数后的黄土孔隙分布均具有良好的统计分形特性。基于热力学模型和毛细管压力曲线法表征黄土孔隙结构时,黄土孔隙呈现显著的分形特性,可在整个孔径尺度范围内给出唯一且合理的分形维数。基于Menger海绵模型表征的经历冻融作用后黄土孔隙分形特征呈现多尺度分形,在不同的尺度范围内,有不同的分形维数。结合分形理论可知冻融作用改变了黄土孔隙均匀性及复杂程度。

关键词: 黄土, 冻融循环, 压汞试验, 孔隙率, 分形模型

Abstract: In order to obtain the effect of freezing-thawing cycles on the pore size distribution of loess, remolded loess was taken as the research object, the pore characteristics of loess samples after different freeze-thaw cycles were tested by mercury intrusion porosimetory. In addition, quantitative characterization and comparative study of microscopic pore structure of loess were carried out by using three kinds of fractal models. The results showed that the pore distribution curve of loess without freezing-thawing action is unimodal, while the pore distribution curve of loess subjected to freezing-thawing was bimodal or even multimodal. The freezing-thawing cycle has a considerable influence on the pore size within the range of 0.1~10?m in loess. The porosity of loess increased during the first ten freezing-thawing cycles, especially after six freezing-thawing cycles, the porosity increased by about 18.8%. As freezing-thawing continued, the porosity of loess decreased and stabilized. The pore size distribution of loess after different freezing-thawing cycles exhibits a good statistical fractal characteristics. Based on the thermodynamic model and capillary pressure curve method to characterize the pore structure of loess, the loess pores exhibit significant fractal characteristics and can give a unique and reasonable fractal dimension over the entire pore size scale. However, while the menger sponge model is adopted, the fractal characteristics of loess pores exhibit multi-scale fractal, and there are different fractal dimensions in different scales. Combined with fractal theory, it can be concluded that freezing-thawing changes the porosity uniformity and complexity of loess.

Key words: loess, freeze-thaw cycle, mercury intrusion porosimetry, porosity, fractal model