The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage.

中文翻译：

---

一种考虑初始损伤和损伤演化的改进的岩石非线性损伤模型

实验结果表明，岩石蠕变特性受初始损伤的影响，损伤演化对蠕变过程中岩石的时变特性也有显着影响。然而，目前对岩石蠕变模型的研究很少考虑初始损伤和损伤演化的影响。本文根据不同损伤程度砂岩的多级蠕变试验结果，提出了一种新的非线性蠕变损伤模型。新的非线性蠕变损伤模型是在 Nishihara 模型的基础上改进的。考虑了初始损伤和损伤演化对 Nishihara 模型中部件的影响。蠕变损伤模型不仅可以描述三个蠕变阶段的变化，即初级蠕变、次级蠕变、和三次蠕变，也反映了初始损伤和损伤演化对蠕变破坏的影响。非线性最小二乘法用于确定非线性蠕变损伤模型中的参数。实验数据与预测结果的一致性表明非线性损伤模型适用于准确预测初始损伤岩石蠕变变形。