节理岩体弹塑黏性疲劳本构模型研究

Research on elasto-plastic viscous fatigue constitutive model of jointed rock

在疲劳荷载作用下节理岩体具有明显的瞬时塑性应变,有必要研究考虑瞬时塑性的节理岩体疲劳本构模型。提出节理塑性疲劳元件和双触发非线性黏性疲劳组合元件,假定节理塑性应力与应变成幂函数关系,加速疲劳应变为二阶非线性黏性应变。通过并联圣维南体改进伯格斯疲劳模型模拟稳定疲劳。在此基础上,提出并验证了一种新的节理岩体弹塑黏性疲劳本构模型。研究表明:该模型能较好地模拟完整岩石、节理岩体试验疲劳应变。该模型可以较好模拟疲劳加载条件下节理岩体稳定疲劳曲线,也可以较好模拟节理岩体非稳定疲劳的瞬时弹性和瞬时塑性应变、减速疲劳阶段应变、等速疲劳阶段与加速疲劳阶段应变。该模型拟合结果表明:节理岩体的疲劳瞬时塑性应变在疲劳瞬时应变中占较大比例,不能忽略其对疲劳应变的影响。该研究结果对预测节理岩体工程的疲劳变形和疲劳稳定性具有参考价值。

The jointed rock mass exhibits an obviously instantaneous plastic strain under fatigue loading,and thus it is imperative to establish a fatigue constitutive model of jointed rock considering instantaneous plasticity.Based on the assumption that the relationship between the plastic stress of the joint and stress follows a power function,and the accelerated fatigue strain is a second-order nonlinear viscous strain,a joint plastic fatigue component and a double-triggered nonlinear viscous fatigue composite component are proposed.Then a new elastic-plastic viscous fatigue model of jointed rock is established.The results reveal that the proposed model can accurately simulate the fatigue strain of intact rock and jointed rock.Moreover,the proposed model can simulate the stationary fatigue curve of jointed rock mass under fatigue loading,and it can also be applied in the simulation of instantaneous elastic-plastic fatigue,decelerated fatigue,constant speed fatigue and accelerated fatigue of jointed rock under non-stationary fatigue.The model fitting results show that the instantaneous fatigue plastic strain of jointed rock accounts for a large proportion of the instantaneous fatigue strain which should not be ignored.The results of this study are of great reference value in the prediction of fatigue strain and fatigue stability of jointed rock in rock engineering.