冻结过程中单孔冰结晶变形机制研究

孔隙水在冻结过程中产生的冰结晶压力导致了多孔材料的冻胀及破坏。本文通过理论分析分别给出了不同形状晶体的结晶压力计算模型，并分析了经典结晶压力计算公式的使用条件。建立了降温过程中孔隙冰晶生长模型，实现冰晶生长过程中的孔隙变形计算，分析了晶核密度、孔径大小、荷载和冰晶体积对孔隙冻胀变形的影响机制。结果表明：起始孔隙直径和长宽比的增大对结晶变形抑制作用的机理在于减少了冰晶体积中膨胀结晶的比例。荷载对孔隙变形的抑制机制在于，荷载的增大迫使冰晶更多地横向生长（长宽比增大），导致膨胀结晶所占比例减小。孔隙中的晶体生长有完全填充模式和部分填充模式，在部分填充模式下，晶核密度、荷载和孔径的增大都会导致晶体在孔隙中的填充率增大，从而对孔隙结晶变形产生影响。本模型揭示了单个孔隙中冻胀变形机制，为解决多孔介质的冻胀变形与破坏问题提供了新的思路。

The study of deformation mechanism of ice crystals in a freezing single pore

The crystallization pressure on the surface of the pore wall lead to the frost heave of porous materials during the growth of ice crystals in the cooling process. In this paper， the calculation models of crystallization pressure for crystals of different shapes are given respectively， and the application conditions of the classical calculation formula of crystallization pressure are analyzed. Then， based on crystallization kinetics theory and considering the interaction between crystal and pore wall， a growth model of pore ice crystallization during the cooling process was established to calculate the pore deformation during the growth of ice crystals， and the influence mechanism of crystal nucleus density， pore size， load and freezing amount on the pore crystallization deformation was analyzed. The results show that the increase of initial pore diameter and aspect ratio inhibits crystallization deformation by decreasing the proportion of expanded crystals in ice crystal volume. The inhibition mechanism of load on pore deformation is that the increase of load forces salt crystals to grow more laterally （the length-to-width ratio increases）， leading to the decrease of the proportion of expansive crystals.There are two modes of crystal growth in the pore： full filling mode and partial filling mode. In the partial filling mode， the increase of crystal nucleus density， load and pore size will lead to the increase of crystal filling rate in the pore， thus affecting the pore crystallization deformation. This model reveals the deformation mechanism of ice crystals in a freezing single pore， which provides a new idea for solving the problem of frost heave deformation and failure of porous media.