基于应力与时间双阈值的岩石全时态非线性蠕变损伤模型

Full-time nonlinear creep damage model of fractured rock mass based on stresstime double threshold

为了更恰当地描述岩石蠕变损伤过程的非线性变形规律,建立损伤因子与时间的函数,以应力和时间作为控制因素对岩石蠕变阶段进行重新划分,引入瞬时塑性体元件改进Bingham体,串联村山体以及CYJ体分别对蠕变各阶段进行描述,并结合损伤理论对模型中的弹性元件和黏性元件进行处理,建立岩石的一维和三维非线性蠕变损伤模型本构方程。通过室内三轴压缩蠕变分级加载及卸载试验给出岩石蠕变过程中村山体,CYJ体的弹性元件和黏性元件参数演化规律,以及损伤效应的累积发展趋势,并对该过程进行参数识别,对比验证所建立模型的可行性与正确性。研究表明:模型中村山体弹性元件的硬化作用与黏性元件的损伤作用,两者之间的动态演化构成了岩石等速蠕变阶段的变形特点,表现在等时应力–应变曲线中两拐点之间的平衡关系;CYJ体中时间与应力的共同作用促进了黏性元件与岩石自身损伤之间的相互叠加,进一步削弱岩石抵抗变形的能力,从损伤累积发展曲线上可以得到验证,随着应力的增大和时间效应的显现,岩石损伤累积呈现指数增加,岩石的蠕变过程是关于损伤产生→扩散→累积→释放的全过程。在模型参数识别验证中,拟合曲线与试验曲线的相关系数R2达到了0.982,验证了构建的全时态非线性蠕变损伤模型的可行性。采用非线性元件和损伤力学处理相结合的方法来构建岩石的全时态非线性蠕变损伤模型,不仅能够表征整个蠕变过程的损伤演化,而且能够准确描述岩石加速蠕变阶段的非线性变形规律,是对蠕变模型构建方法的一种新的尝试。

In order to more appropriately describe the nonlinear deformation law of the rock creep damage process and to establish a function between damage factor and time,the stress and time are used as controlling factors to re-divide the rock creep stages,and the instantaneous plastic element is introduced to improve Bingham body.Improved Bingham body,Murayama body and CYJ body are held together to describe each stage of creep respectively.Then,elastic and viscous components in the model are treated by damage theory.The one-dimensional and three-dimensional nonlinear creep damage model principal structure equations of the rock are established.By indoor triaxial compression creep graded loading and unloading tests,the evolution law for elastic and viscous element parameters(Murayama body,CYJ body)during rock creep are given.Then,obtained the cumulative development trend of the damage effect,which can be identified the process parameters.Last,the feasibility and correctness of the established model are verified by comparison.The study shows that:the hardening effect of the elastic element and the damage effect of the viscous element in the Murayama body,the dynamic evolution between the two constitutes the deformation characteristics of the isokinetic creep phase of the rock,which is manifested in the equilibrium relationship between the two inflection points of isochronous stress-strain curve.Between the viscous element and the rock's own damage,the joint action of time and stress in the CYJ body promotes the mutual superposition,further weakening the rock¢s resistance to deformation,which can be verified from the damage accumulation development curve.By stress increase and time effect,the rock damage accumulation shows exponential increase,the creep process of the rock becomes the whole process of damage generation→diffusion→accumulation→release.In the model parameter identification and verification,the correlation coefficient R2 reached 0.982 with the fitted curve and the test curve,which verified the feasibility of the constructed all-time nonlinear creep damage model.A full-temporal nonlinear creep damage model for rocks,constructed by nonlinear components and damage mechanics treatment,can not only characterize the damage evolution of the whole creep process,but also accurately describe the nonlinear deformation law of the accelerated creep stage of rocks.This is new attempt to the creep model construction method.