为研究砂岩在深部高应力环境下的蠕变变形特征和黏弹塑性变形规律，对砂岩试件还原初 始应力后采用分级增量加卸载的方式，进行三轴压缩蠕变试验。 根据试验结果将应变分解为瞬弹 性应变、瞬塑性应变、黏弹性应变和黏塑性应变，采用稳态蠕变速率法测算了深部砂岩的长期强度， 并验证了基于分数阶模型改进的深部砂岩蠕变模型的适用性，对比分析了西原模型与改进后的深 部砂岩蠕变模型对试验数据的拟合效果。 结果表明:砂岩蠕变过程中，瞬时弹性应变阶段变形量最 大，占总变形量的 70% ~ 80%;随着加载等级的增加，深部岩石试件瞬弹性应变和瞬塑性应变都逐 渐增加，但瞬塑性应变增量先减小后增大，说明在加载过程中试件内部有瑕疵的微元体被破坏;随 着应力增加，不可恢复的黏性流动增强，黏塑性应变增长较快，塑性变形堆积，到高应力水平蠕变变 形表现为黏弹性变形和黏塑性变形共存的状态;通过对稳态蠕变进行分析，得到砂岩试件稳态蠕变 速率不为零的应力阈值，以此为测算深部砂岩长期强度的依据，测算得到深部砂岩的长期强度为 66 MPa，约为常规强度的 77%。 通过最小二乘法对数据进行深部砂岩蠕变模型和西原模型的拟合 与参数辨识，得出改进后分数阶模型可以更好地描述深部砂岩的等速蠕变和加速蠕变。

To study the creep deformation characteristics and visco⁃elastic⁃plastic deformation law of sandstone under deep high stress environment，the triaxial compression creep tests were conducted on sandstone specimens after the ini⁃ tial stress was restored by step increment loading and unloading method. According to the test results，the strain was decomposed into instantaneous elastic strain，instantaneous plastic strain，sticky glue elastic strain and plastic strain for further analysis. The steady⁃state creep rate method was used to estimate the long⁃term strength of deep sandstone，and verify the model based on fractional order to improve the applicability of the deep sandstone creep model. Contrast was conducted to analyze the fitting effect of the Nishihara model and the improved deep sandstone creep model on the test data. The results show that in the creep process of sandstone，in the instantaneous elastic strain stage the deformation is maximal，which accounts for 70% to 80% of the total deformation. With the loading level increasing，the transient elas⁃ tic strain and the transient plastic strain of the deep rock specimen increase gradually. However，the increment of the transient plastic strain decreases first and then increases，indicating that the defective microelements in the specimen are destroyed during loading. With the stress increasing，the unrecoverable viscous flow becomes stronger. Moreover， the viscoplastic strain increases rapidly and the plastic deformation accumulates. When reaching the high stress level， the creep deformation shows the coexistence of viscoelastic deformation and viscoplastic deformation. By analyzing the steady⁃state creep，the stress threshold when the steady⁃state creep rate is not zero was obtained. It was regarded as the basis to calculate the long⁃term strength of deep sandstones. It was estimated that the long⁃term strength of deep sand⁃ stone is 66 MPa，around 77% of conventional strength. The least square method was used to fit the creep model and the Nishihara model of deep sandstones and identify the parameters. It is concluded that the improved fractional model can better describe the constant velocity creep and accelerated creep of deep sandstones.