The fatigue characteristics of rock materials are usually studied by cyclic load–unload tests, and the deformation and damage development reflect their weakening characteristics. In this paper, according to the mechanical characteristics of rock materials during load/unload cycles, the total strain can be separated into three types, that is, elastic strain, viscoelastic strain, and viscoplastic strain. The elastic strain is linear with stress, and viscoelastic strain exhibits a special behavior after unloading, the viscoplastic strain also displays its own unique features and reflects the damage in rocks. Based on their unique characteristics, we establish elastic, viscoelastic, and viscoplastic submodels, then an elastic-visco-plastic model can be obtained by connecting three submodels in series, which can reflect the development of the law of different strains. In order to verify the reliability of the model, red sandstone samples are selected for cyclic load/unload tests. The results show that the collected strain–time data are well fitted by the model. In addition, the characteristics of strain–time curves imply the deformation and damage development of rocks during load/unload cycles.

岩石材料的疲劳特性通常通过循环加卸载试验研究，其变形和损伤发展反映了它们的弱化特性。根据岩石材料在加载/卸载过程中的力学特性，总应变可以分为三种类型，即弹性应变，粘弹性应变和粘塑性应变。弹性应变与应力成线性关系，粘弹性应变在卸荷后表现出特殊的行为，粘塑性应变也表现出其独特的特征并反映了岩石的破坏。根据它们的独特特征，我们建立了弹性，粘弹性和粘塑性子模型，然后可以通过串联三个子模型来获得弹性-粘塑性模型。可以反映出不同品系的规律的发展。为了验证模型的可靠性，选择了红砂岩样本进行循环加载/卸载测试。结果表明，所收集的应变时间数据与模型完全吻合。此外，应变-时间曲线的特性暗示了岩石在加载/卸载循环过程中的变形和破坏的发展。