The behavior of water and salt inside porous sandstone is crucial for determining the durability of stone heritage. This involves multiphase coupled processes, yet previous analyses have paid insufficient attention to the spatial and temporal characterization of solution-crystal phase change. Based on the salt crystallization experiments, theoretical models and numerical computational frameworks are synthesized to simulate multiphase processes. Subsequently, equations are established for coupled water-salt-heat-mechanical interactions in the multiphase media. Then, the critical state of solution-crystal phase change is analyzed through the evolution of saturation, crystallization pressure, and porosity. The findings indicate rapid solution saturation growth at positions with minimal wetting front fluctuations, leading to initial crystallization. Further tracing reveals that crystallization evolves through discrete crystallization, annular crystallization, and crystallization expansion stages. By investigating the crystallization pressure and the crystal morphology, it is possible to quantify the dynamics of crystal pressure on constraint surfaces and solution pressure. In addition, the change in porosity can be observed by simulation of dry and wet cycles to obtain crystallization initiation. The numerical calculations agree well with the experimental results, providing valuable insights into the deterioration mechanism induced by salt crystallization in the porous sandstone of Dazu Rock Carvings.

中文翻译：

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盐相变引起多孔砂岩内部结晶的数值分析


多孔砂岩内水和盐的行为对于确定石材遗产的耐久性至关重要。这涉及多相耦合过程，但以前的分析对溶液-晶体相变的空间和时间特征的关注不够。基于盐结晶实验，综合理论模型和数值计算框架来模拟多相过程。随后，建立了多相介质中水-盐-热-机械耦合相互作用的方程。然后，通过饱和度、结晶压力和孔隙率的演变来分析溶液-晶体相变的临界状态。研究结果表明，在润湿前沿波动最小的位置，溶液饱和度快速增长，导致初始结晶。进一步追踪表明，结晶过程经历了离散结晶、环形结晶和结晶膨胀阶段。通过研究结晶压力和晶体形态，可以量化约束表面上晶体压力和溶液压力的动态。此外，可以通过模拟干湿循环来观察孔隙率的变化以获得结晶引发。数值计算与实验结果吻合较好，为大足石刻多孔砂岩盐结晶引起的劣化机理提供了有价值的见解。