冻融作用下砂土颗粒形态变化规律研究

土壤中的石英颗粒的表面形态不仅是该沉积物物源区沉积环境、 搬运机制的信息载体， 同时也会直接影响到砂土的宏观物理特性， 对力学和实际工程有着重要的意义。借助显微与高精度图像处理技术， 采用长径比， 磨圆度两个量化指标， 对经过不同次数冻融作用的两组砂土颗粒进行观察。结果表明： 砂土颗粒在冻融循环过程中， 由于颗粒之间的相互作用， 磨圆度先增大后减小， 最后趋于稳定； 长径比先减小， 后增加， 最后趋于稳定。长径比与磨圆度的变化曲线共轭。

Experimental study on morphometric changes of sand particles under freezing-thawing cycles

The surface morphology of quartz particles in the soil is not only the information carrier of the sedimentary environment and transport mechanism from the sediment source area， but also directly affects the macroscopic physical property of the sand， which is of great significance to mechanics and practical engineering. Scanning electron microscope was used in this paper and two quantitative indexes， aspect ratio and psephicity， were used to observe two groups of sand particles subjected to different freezing-thawing cycles. It is hoped that by observing and studying the sand particles under different freeze-thaw cycles， the variation of the surface morphology of sand particles due to freezing-thawing have been summarized， which will provide theoretical basis for future studying the historical changes and paleoclimate environment in glacialized and frozen soil areas. It also provides theoretical support for the practical engineering application in seasonal frozen soil areas. It is shown that during the freezing-thawing， the psephicity of sand particles first increases， then decreases and finally tends to be stable due to the interaction among the particles. The aspect ratio first decreases， then increases， and finally stabilizes. The aspect ratio conjugates with the curve of psephicity. At the same time， during the freezing-thawing cycles， the frictional action among the particles occurs first， and then the great stress among the particles causes the particles to break down. The number of freezing-thawing cycles required for the crushing of coarse sand particles is obviously less than that of fine sand particles. With the increase of freezing-thawing cycles， the dynamic equilibrium of damage-grinding tends to be stable.