The relaxation test on sandstone specimens showed typical behavior in pre-failure region and stepwise behavior in the post-failure region. Overall, more significant stress relaxation occurred within the failed specimens than the intact ones. Numerical simulations were conducted with pre-defined failure plane and with Voronoi tessellation to visualize the relaxation behavior. The model with pre-defined failure plane showed the key role of failure plane and asperity in simulating the step-wise post-failure relaxation behavior. The inhomogeneous stress distribution within failed specimen and the viscous deformation of intact rocks induced high stress concentration at the asperities. The observed step-wise relaxation initiated from the failure of asperity. Furthermore, the simulations with Voronoi tessellation showed time-dependent fracture development during relaxation in post-failure region. The presence of fractures completely changed the stress distribution. Stress concentration occurred at the front area of fractures and at the interacting areas between fractures. During relaxation, fractures still developed with time and the sudden significant increase in the “damage” coincided with the acceleration of stress relaxation leading to step-wise relaxation. Finally, the results showed the possibility of using residual strength as the long-term strength of failed rock.

中文翻译：

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失效砂岩试样松弛行为的数值模拟

砂岩试样的松弛试验在破坏前区域表现出典型行为，在破坏后区域表现出阶梯行为。总体而言，与完整试样相比，失效试样内发生了更显着的应力松弛。使用预定义的失效平面和 Voronoi 细分进行数值模拟，以可视化松弛行为。具有预定义失效平面的模型显示了失效平面和粗糙度在模拟逐步失效后松弛行为中的关键作用。破坏试样内部的不均匀应力分布和完整岩石的粘性变形导致粗糙处的高应力集中。观察到的逐步松弛是从粗糙的失效开始的。此外，使用 Voronoi 镶嵌的模拟表明，在失效后区域的松弛过程中，断裂发展与时间有关。裂缝的存在完全改变了应力分布。应力集中出现在裂缝的前缘和裂缝之间的相互作用区域。在松弛过程中，裂缝仍然随着时间的推移而发展，“损伤”的突然显着增加与应力松弛加速导致逐步松弛相吻合。最后，结果表明了将残余强度用作破坏岩石的长期强度的可能性。裂缝仍然随着时间的推移而发展，“损伤”的突然显着增加与应力松弛加速导致逐步松弛相吻合。最后，结果表明了将残余强度用作破坏岩石的长期强度的可能性。裂缝仍然随着时间的推移而发展，“损伤”的突然显着增加与应力松弛加速导致逐步松弛相吻合。最后，结果表明了使用残余强度作为破坏岩石的长期强度的可能性。