酸性环境下黄土细观结构演变的定量研究

Quantitative Study on Micro Structure Volution of Loess under Acid Environment

研究了酸性环境下黄土的细观结构与宏观物理力学性质的变化特征。对原状黄土进行了不同酸浓度的湿陷试验,采用颗粒分析试验与压汞试验对上述试验土样的SEM扫描照片进行处理,并计算了土样的粒度分维值和大、中孔隙占比。试验测试并计算了不同土样颗粒和团粒间的范德华力与库仑力。从细观定量角度解释了土样粒级熵、排列熵和能级熵的变化特性,从而引起土体宏观性质的变化。结论如下:当应力条件持续变化时,土样颗粒和团粒经历了较大幅度的调整过程,以适应外部应力的变化,这种周期性的变化特征与增湿和加酸条件下黄土结构的变化是一致的;随着压力的增大,含水量的增加,酸性的增强,土颗粒之间的孔隙间距及土粒粒径由此减小;中孔隙和大孔隙的数量和含量均减小,微孔隙以及小孔隙的数量和含量均增加;土颗粒和团粒之间的范德华力与库仑力微重比随之增大。由此证明,黄土在侵酸条件下,内部结构的演变加剧了其宏观物理力学性质的变化。

The characteristics of changes in fine structure and macroscopic physical and mechanical properties of loess under acidic environment were studied. The SEM scans of the above test soil samples were processed by particle analysis tests and mercury compression tests, and the particle size fractional dimensional values and the percentage of large and medium pores of the soil samples were calculated. The Van der Waals and Coulomb forces between particles and agglomerates of different soil samples were tested and calculated. The variation characteristics of grain level entropy, alignment entropy and energy level entropy of soil samples were explained from a fine quantitative point of view, which caused changes in the macroscopic properties of the soil. The conclusions are as follows: when the stress conditions continue to change, the soil sample particles and agglomerates undergo a relatively large adjustment process to adapt to the changes in external stresses, and this periodic change characteristic is consistent with the changes in the structure of loess under humidified and acidified conditions;with the increase of pressure, water content and acidity, the pore spacing between soil particles and the soil particle size decrease as a result;the number and the content of medium and large pores. The number and content of mesopores and macropores decreased, and the number and content of micropores and small pores increased;the van der Waals force and Coulomb force microgravity ratio between soil particles and agglomerates increased. This proves that the evolution of the internal structure of the loess under acid attack conditions exacerbates the changes in its macroscopic physical and mechanical properties.