Time-dependent rock deformation affects both natural processes happening on the geological time scale and subsurface engineering operations. We perform a series of multistage triaxial experiments on a set of natural limestone and artificial samples. We study rock response during creep and stress relaxation tests, which are two endmembers of time-dependent rock response. The tests were conducted at room temperature and low confining pressure. We find that all rock samples showed pronounced creep and stress relaxation both at low-stress levels corresponding to half of the yield stress and higher stresses corresponding to yield stress. Associated values of bulk and shear viscosities lie in the range of 10¹⁵–10¹⁷ Pa s for artificial and 10¹⁵–10¹⁶ Pa s for limestone samples at critical stresses corresponding to failure limits. At low stresses, effective viscosities are significantly higher. Bulk viscosity is up to two times higher than shear viscosity. Viscosity values correlate well with failure properties. Samples with low strength show the lowest values of viscosities. All samples exhibited significant dilation during creep experiments, which was not associated with the formation of the macroscale fracture or strain localization. Creep and stress relaxation tests show different stress–strain rate behavior.

随时间变化的岩石变形影响地质时间尺度上发生的自然过程和地下工程操作。我们对一组天然石灰石和人造样品进行了一系列多级三轴实验。我们研究蠕变和应力松弛试验期间的岩石响应，这是随时间变化的岩石响应的两个端元。试验在室温和低围压下进行。我们发现所有岩石样品在对应于屈服应力一半的低应力水平和对应于屈服应力的较高应力下均表现出明显的蠕变和应力松弛。体积粘度和剪切粘度的相关值范围为 10 ¹⁵ –10 ¹⁷  Pa s（人造）和 10 ¹⁵ –10 ¹⁶ 石灰石样品在临界应力下对应于破坏极限的 Pa s。在低应力下，有效粘度显着更高。体积粘度比剪切粘度高两倍。粘度值与失效特性密切相关。低强度的样品显示出最低的粘度值。所有样品在蠕变实验期间都表现出显着的膨胀，这与宏观断裂或应变局部化的形成无关。蠕变和应力松弛测试显示不同的应力应变率行为。