一种基于能量耗散理论的岩石加速蠕变模型

Accelerated creep model of rock based on energy dissipation theory

岩石加速蠕变阶段的启动条件是分析蠕变全过程的难点问题,现有的西原体模型在描述岩石黏塑性阶段的加速蠕变特性时也存在明显的不足。为了更好地描述岩石蠕变的全过程、划分蠕变的不同阶段和表征加速蠕变阶段的变形特性,基于能量耗散理论定义了加速蠕变启动的控制阈值,将Perzyna黏塑性模型引入西原体模型,由此构建了一种新型的岩石加速蠕变本构模型,并且通过三轴逐级加载蠕变实验数据对模型进行了验证。结果表明:蠕变加载过程中的能耗和蠕变损伤主要来源于岩土类材料内部的内能变化,基于能量耗散理论和考虑蠕变速率变化构建的岩石加速蠕变模型能更好地描述岩石黏弹塑性蠕变特性,不仅反映了岩石能量耗散与蠕变变化之间的关系,也进一步突出了岩石的蠕变速率和蠕变应力状态对加速蠕变的影响;同时,该模型克服了传统的西原模型难以描述加速蠕变变形特征的缺点,更加准确地反映了岩石的衰减和稳定蠕变阶段的蠕变特性;最后,对比分析结果验证了采用耗散率值来定义由稳定蠕变阶段转化为加速蠕变阶段的控制阈值是可行的,引入Perzyna黏塑性模型对改善西原体模型描述岩石加速蠕变阶段的变形特征是有效的,研究结果为分析蠕变变形全过程和划分蠕变变形阶段提供了一个新方法,为研究蠕变模型和蠕变力学特性提供了一个新思路。

The starting condition of the rock accelerated creep stage is a difficult problem in analyzing the whole process of creep.The existing Nishihara model has obvious shortcomings in describing the accelerated creep characteristics of the rock viscoplastic stage.In order to better describe the whole process of rock creep,divide the creep into different stages and characterize the deformation characteristics of accelerated creep stage,the control threshold of accelerated creep start was defined based on the energy dissipation theory.A new model of rock ac-celerated creep constitutive model was constructed by introducing the Perzyna viscoplastic model into the Nishihara model.The model was verified by a three-axis progressive loading creep experiment.The results showed that the energy consumption and creep damage during creep loading were mainly derived from the internal energy changes inside the geomaterial.The rock accelerated creep model based on energy dissipation theory and considering creep rate changes could better describe the viscoelastic-plastic creep properties of rock.The model not only reflected the relationship between rock energy dissipation and creep variation,but also highlighted the effects of creep rate and creep stress state on accelerated creep.The model overcome the shortcomings of the traditional Nishihara model which was difficult to describe the characteristics of accelerating creep deformation.Also,it more accurately reflected the creep characteristics of the attenuation and stable creep stages.The comparative analysis results verified that it was feasible to use the dissipation rate value to define the control threshold from the stable creep phase to the accelerated creep phase.The introduction of the Perzyna viscoplastic model was effective for improving the deformation characteristics of the rock specimen during the accelerated creep stage of the rock model.The research results provide a new method for analyzing the whole process of creep deformation and the stage of creep deformation,and also provide a new idea for studying creep model and creep mechanics.