Rock salt, due to its water solubility, low permeability, high plasticity, and damage self-healing ability, is one of the best candidate rock types for underground energy storage. Utilizing salt caves to construct compressed air energy storage (CAES) facilities can effectively enhance the utilization of renewable energy. Due to the need for peak shaving, the surrounding rock of the salt cavern will undergo discontinuous cyclic loading with varying gas injection rates and pressures, namely, alternating creep–fatigue loading. Considering the actual peak-shaving cycle of a CAES plant, long-term creep–fatigue tests of rock salt with different loading cycles and stress levels were conducted. The results indicate that in long-term creep–fatigue tests for rock salt, the lower the loading stress rate is, the greater the deformation of the rock salt. The variation in the stress limit has a greater effect on creep than on fatigue loading and unloading. The deformation rate of rock salt is influenced by alterations in the stress state. Based on the test results, according to the Norton creep model, a new creep–fatigue constitutive model for rock salt was established by defining a state variable that characterizes the level of rock hardening and introducing unloading as well as crack factors. This model can accurately describe the impact of historical loading and unloading processes on the viscoplastic mechanical characteristics of rock salt. The rock salt creep–fatigue test results were used to verify the constitutive model. A comparison of the fitting curve of the different stress loading paths with the test curve reveals good consistency, indicating that the model comprehensively considers the effects of time, load, and state on rock salt creep–fatigue, effectively describing the viscoplastic deformation characteristics of rock salt under different stress paths. These research findings provide important guidance for ensuring the stability of salt caverns used for CAES.

中文翻译：

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蠕变疲劳应力加载路径下岩盐的长期变形：建模和预测


岩盐由于其水溶性、低渗透性、高塑性和损伤自修复能力，是地下储能的最佳候选岩石类型之一。利用盐洞建设压缩空气储能（CAES）设施可以有效提高可再生能源的利用。由于调峰的需要，盐穴围岩将承受不同注气量和压力的间断循环加载，即交替蠕变疲劳加载。考虑CAES装置的实际调峰周期，对不同加载周期和应力水平的岩盐进行了长期蠕变疲劳试验。结果表明，在岩盐的长期蠕变疲劳试验中，加载应力率越低，岩盐的变形越大。应力极限的变化对蠕变的影响比对疲劳加载和卸载的影响更大。岩盐的变形速率受应力状态变化的影响。根据试验结果，根据诺顿蠕变模型，定义表征岩石硬化水平的状态变量，引入卸载因子和裂纹因子，建立了新的岩盐蠕变疲劳本构模型。该模型能够准确描述历史加卸载过程对岩盐粘塑性力学特性的影响。岩盐蠕变-疲劳试验结果用于验证本构模型。 不同应力加载路径的拟合曲线与试验曲线的比较显示出良好的一致性，表明该模型综合考虑了时间、载荷和状态对岩盐蠕变疲劳的影响，有效地描述了岩石的粘塑性变形特征不同应力路径下的盐。这些研究结果为确保CAES所用盐穴的稳定性提供了重要指导。