基于核磁共振技术的黄土内部孔径分布对逾渗特性的影响
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P64

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面向人地协调的黄土重大工程灾变防控研究(41790445);溃散性滑坡成因机理、监测预警与定量风险评价,(41630640)


Effect of pore size distribution on percolation characteristics of loess based on nuclear magnetic resonance technique
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    摘要:

    黄土的逾渗特性作为黄土渗流中比较特别的性质,它涉及到了黄土渗透性突变的特殊问题,其重要性是毋庸置疑的。研究黄土内部的孔径分布对逾渗特性的影响可以为工程中的某些渗流问题提供理论依据与实践价值,然而前人的研究往往忽视了这部分内容。基于此,本文展开了一组原状黄土和两组重塑黄土的试验研究:采用变水头试验分析黄土渗流过程中的逾渗现象,然后利用核磁共振技术对三组试样进行孔隙分布评价,最终分析孔径分布对于黄土逾渗特性的影响。试验结果表明:(1)原状黄土由于原生结构较好,孔隙大小的分布较重塑黄土更为集中,孔径集中在0.011~ 0.11 μm的中孔隙最多;重塑黄土由于丧失了结构性,部分土颗粒会产生黏聚,从而导致土体内的微孔与大孔的比原状黄土多。(2)由于原状黄土孔隙更为集中,内部孔隙更不容易透水,所以更容易达到临界状态从而使得渗透性发生逾渗,原状黄土的临界水头比相同干密度的重塑黄土更高。而重塑黄土则是干密度越大,孔隙率越低,孔隙越小,临界水头越高。试验利用方便快捷的核磁共振技术,首次分析了黄土内部孔径分布对黄土逾渗特性的影响,富有创新性,试验可靠性高,成果可为黄土重大工程的基础建设中的有关渗流问题提供建议。

    Abstract:

    As a special property of loess permeability, percolation of loess seepage involves the special problem of loess permeability mutation. Research on influence of the pore size distribution of loess on seepage characteristics can provide some theoretical basis for the seepage problems in engineering and the practice value, however, this part is often neglected in previous studies. this paper carried out a set of intact loess and the experimental study of two groups of remodeling loess: seepage phenomenon in the process of loess seepage was analyzed by using variable water head test, and then three sets of sample to make use of nuclear magnetic resonance (NMR) technology evaluation of pore distribution, and final analysis for the loess seepage pore size distribution over the influence of seepage characteristics. The experimental results show that: (1) due to the good original structure of the undisturbed loess, the distribution of pore size is more concentrated than that of the remolded loess, with the pore size concentrated in the middle of 0.011~ 0.11 μm. Due to the loss of the structure of remolded loess, some soil particles will produce cohesion, resulting in an increase in the proportion of micropores and macropores in the soil.(2) because the pores of undisturbed loess are more concentrated and the internal pores are less permeable, it is easier to reach the critical state, which leads to a rapid decline in permeability. The critical water head of undisturbed loess is higher than that of remolded loess with the same dry density. The higher the dry density, the lower the porosity, the smaller the pores and the higher the critical head. In this paper, the effect of pore size distribution on seepage percolation of loess is analyzed for the first time by using convenient and fast nuclear magnetic resonance (NMR) technology.

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何攀,许强,刘佳良,等. 基于核磁共振技术的黄土内部孔径分布对逾渗特性的影响[J]. 科学技术与工程, 2020, 20(30): 12355-12360.
He Pan, Xu Qiang, Liu Jialiang, et al. Effect of pore size distribution on percolation characteristics of loess based on nuclear magnetic resonance technique[J]. Science Technology and Engineering,2020,20(30):12355-12360.

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  • 收稿日期:2020-02-24
  • 最后修改日期:2020-08-03
  • 录用日期:2020-05-02
  • 在线发布日期: 2020-11-23
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