Effect of freezing temperature on mechanical properties of layered hail**

This thesis aims to clarify the influence of layered structure and different freezing temperatures on the mechanical properties of hails. The transparent hails with a diameter of 50 mm and layered hails with distinct structures were prepared using a self-made mold. A series of quasi-static compression experiments were conducted for the simulated hails (both transparent hail and layered hail) through a universal testing machine at different freezing temperatures (-10 °C, -20 °C, -30 °C, -40 °C), and combined with microscopic structure analysis to determine the failure mechanism. Based on the experimental results, it is found that as the freezing temperature decreases, the compressive strength of both transparent hails and layered hails significantly increases. Layered hails are more sensitive to temperature changes. At -40 °C, the average compressive strength of layered hails is approximately 6 times higher than that at -10 °C, while that of transparent hails is approximately 4 times higher. When layered hails fail, they exhibit multiple cracks, while transparent hails have single main crack. The layered structure is rich in bubbles, which can change the crack direction and thereby enhance its compressive strength.