Salt rock is characterized by a low porosity, low permeability and self-healing ability, and it is one of the most common materials used for underground energy storage and construction in underground nuclear waste repositories. Studying the healing of macroscopic cracks in salt rock under different conditions is important for ensuring the stability of the rock surrounding a salt cavern. To evaluate the healing ability and effect of cracks in salt rock at the macroscale, two tests were designed to directly assess the healing ability of salt rock by analyzing the tensile strength and permeability recovery of healed crack surface. Furthermore, the microstructure of the healed macroscopic fractures in salt rock was observed using scanning electron microscopy (SEM), and the microscopic mechanisms of salt rock damage healing were analyzed. (1) The results show that the presence of water is an important condition for the healing of cracks in salt rocks. Fully fractured salt rock cracks can heal at a low pressure of 160 kPa, and the uniaxial tensile strength of the healed specimens can reach a maximum of 121.1 kPa. It was found via computed tomography (CT) that a healed crack was still a weak surface in the whole specimen. (2) Increases in temperature, environmental humidity, and normal stress all promote the self-healing of salt rock fractures. Based on the experimental data, a model describing the evolution of salt rock damage healing variables with respect to temperature, humidity, and stress was established. It was also observed that the change in salt rock damage healing variables over time during the healing process can be represented by a first-order exponential decay function. (3) Using SEM, detailed micro healing experiments were conducted on NaCl single crystal and impurity-containing salt rock specimens. The healing characteristics of intracrystalline cracks and intercrystalline cracks were studied. It was observed that salt rock damage healing manifests at the microscopic level as the filling of microcracks and crack segmentation caused by grain growth. Additionally, the presence of a certain amount of impurities was found to promote the growth of internal structures that heal cracks within salt rock. These findings are of great significance for evaluating the stability and tightness of the surrounding rock of salt cavern reservoirs.

中文翻译：

---

盐岩损伤自修复宏观实验研究与微观现象分析


盐岩具有低孔隙率、低渗透率和自愈能力的特点，是地下储能和地下核废料处置库建设最常用的材料之一。研究不同条件下盐岩宏观裂缝的愈合对于确保盐洞周围岩石的稳定性具有重要意义。为了从宏观上评价盐岩裂缝的愈合能力和效果，设计了两个试验，通过分析愈合裂缝表面的抗拉强度和渗透率恢复来直接评估盐岩的愈合能力。此外，利用扫描电子显微镜（SEM）观察了盐岩宏观裂缝愈合后的微观结构，分析了盐岩损伤愈合的微观机制。 (1)结果表明，水的存在是盐岩裂缝愈合的重要条件。完全破裂的盐岩裂缝可以在160 kPa的低压下愈合，愈合后试件的单轴拉伸强度最高可达121.1 kPa。通过计算机断层扫描（CT）发现，已愈合的裂纹仍然是整个样本中的薄弱表面。 (2)温度、环境湿度和正应力的升高均促进盐岩裂隙的自愈。根据实验数据，建立了一个描述盐岩损伤愈合变量随温度、湿度和应力演化的模型。还观察到，在愈合过程中盐岩损伤愈合变量随时间的变化可以用一阶指数衰减函数表示。 (3)利用SEM对NaCl单晶和含杂质盐岩标本进行了详细的微观愈合实验。研究了晶内裂纹和晶间裂纹的愈合特性。据观察，盐岩损伤愈合在微观层面表现为微裂纹的填充和晶粒生长引起的裂纹分割。此外，还发现一定量杂质的存在可以促进内部结构的生长，从而治愈盐岩内的裂缝。这些发现对于评价盐穴储层围岩的稳定性和致密性具有重要意义。