基于应变软化指标的岩石非线性蠕变模型

研究并提出一种以应变软化指标为基础的岩石非线性蠕变模型。首先，基于岩石三轴压缩试验结果，分析提出一种峰后应变软化指标R1来描述岩石峰后力学参数软化与塑性变形间的关系。接着，通过分析加速蠕变阶段与峰后段的联系，建立加速蠕变应变软化指标R2，并以此为基础构建非线性黏塑性体。然后，将其与Hook体和Kelvin元件串联，组建非线性蠕变模型，并将模型嵌入ABAQUS有限元程序。最后，针对砂岩和泥岩三轴蠕变试验建立数值模型，模拟曲线与试验曲线吻合良好，说明所建模型适用于硬岩/软岩加速蠕变现象的模拟。其中，参数 对加速蠕变曲线形态起调节作用，显示模型模拟脆性?延性流变破坏的特点。另外，模型参数均可由常规压缩破坏试验以及蠕变试验确定，易于获取。

A nonlinear creep model of rock based on the strain softening index

A nonlinear creep model is researched and proposed on the basis of a new proposed strain softening index. Firstly, according to the triaxial experimental data of rock, a strain softening index R1 is presented to describe the relationship between the softening of the post-peak mechanical parameters and the plastic strain. Secondly, by analyzing the relationship between the tertiary creep and the general post-peak stage, a strain softening index R2 in the tertiary creep is put forward to establish a non-linear viscoplastic element. Thirdly, by connecting the nonlinear viscoplastic element with the Hook and the Kelvin viscoelastic models, a nonlinear creep model is established inserting into the ABAQUS software. Finally, the proposed model is applied to simulate the triaxial creep experiments of sandstone and mudstone. The numerical results are in good agreement with the experiments indicating that the proposed model is capable of characterizing the accelerated creep behaviors of hard and soft rocks. The parameter β can adjust the curve form of the tertiary creep, showing the function to model the brittle-ductile failure. Furthermore, the parameters in the model can be readily identified by the conventional compression failure test and the creep test.