冻融循环导致颗粒破碎和团聚的过程中，将会显著改变颗粒的尺寸和形态。为研究冻融循环对颗粒尺寸和形态的影响规律，试验选用青藏粉土为研究对象，分别进行0、1、5、10、50、100次封闭系统下的自由冻融循环试验。对冻融后的试样采用移液管法进行粒度成分测试后，采用PIP9.1型颗粒图像处理仪进行长径比、圆度等颗粒形态参数测试分析。试验结果表明：冻融作用导致颗粒的棱角边缘发生破碎，粒径小于0.001 mm的颗粒质量百分比增大。颗粒长径比主要分布在1~3之间，占比94%以上，且长径比的半对数柱状图符合正态分布。圆度分布在0.09~1之间，且100次冻融循环后颗粒的平均圆度增大。100次冻融循环后，颗粒的长径比及尺寸减小，圆度增大，颗粒形状趋近于圆形。整体发现经过冻融的过程中青藏粉土颗粒在发生团聚和分裂的过程中，伴随着强烈的磨圆作用。

During the freeze-thaw cycles leading to particle fragmentation and aggregation， the size and morphology of particles will be significantly changed. In order to study the influence of freeze-thaw cycles on particle size and morphology， the Qinghai-Xizang silt was selected for 0， 1， 5， 10， 50 and 100 free freeze-thaw cycles under closed system. After the particle size composition was tested by the liquid transfer tube method， the PIP9.1 particle image processor was used to collect the shape parameters such as particle aspect ratio and roundness. The experimental results are as follows： The freeze-thaw action caused the angular edges of the particles to be broken， and the mass percentage of particles with particle size less than 0.001 mm increased. The particle aspect ratios were mainly distributed between 1 and 3， accounting for more than 94%， and the semi-logarithmic histogram of the aspect ratios conformed to the normal distribution. Roundness was distributed between 0.09~1， and the average roundness of the particles increased after 100 freeze-thaw cycles. After 100 freeze-thaw cycles， the particle aspect ratio and particle size decrease， the roundness increases， and the particle shape tends to be round. It is found that during the freezing and thawing process， the Qinghai-Xizang silt particles are fragmented and aggregated， accompanied by a strong rounding effect.