基于应变屈服临界的岩石黏弹塑性蠕变模型研究

为了研究岩石的非线性加速蠕变特性, 依据岩石蠕变变形不同阶段的力学特征,划分出了岩石由变形发展至破裂需经历的不同黏弹塑性状态,并给出了相应状态的蠕变力学特性。假定岩石在三轴压缩试验条件下,发生延性剪切破坏,推导了应变空间Drucker-Prager准则的临界状态转化的最大剪应变判别式。基于Perzyna黏塑理论,考虑后继屈服硬化作用,引入统计损伤因子,构建了能描述非线性加速蠕变特性的黏弹塑性损伤演化模型;采用岩石全自动伺服三轴蠕变试验机对三峡库区典型砂岩试样开展了蠕变试验,得到了岩石试样在不同应力水平作用下的蠕变变形曲线。结果表明:蠕变试验中,岩样力学性质的时效特征显著,在最后一级应力水平作用下发生了非线性加速蠕变现象。基于提出的黏弹塑性蠕变模型对试验曲线进行拟合,拟合结果说明模型能够较好地反映砂岩蠕变3个阶段变形的规律特征,拟合效果较好。

Visco-elastic-plastic Creep Model of Rock Based on Strain Yield Critical Criteria

According to rock mechanical characteristics of creep deformation at different stages,the visco-elasticplastic states from deformation to rupture are classified,and the corresponding creep mechanical properties at different states are given.Under the assumption that ductile shear failure occurs in triaxial compression test,the maximum principal strain discriminant for the critical state transformation is derived using Drucker-Prager strain criterion.Furthermore,a visco-elastic-plastic damage evolution model for describing the nonlinear acceleration creep behavior is constructed by introducing a statistical damage factor based on the theory of Perzyna in consideration of the hardening effect in subsequent yield.Moreover,triaxial creep test is Conducted with sandstone specimens from the Three Gorges Reservoir area,and the creep deformation curves under different pressures are acquired.Test results show that the creep characteristics of rock specimens are obvious,and non-linear accelerated creep happened under the final stress level.The proposed model is used for the fitting of test creep curves,and the fitting results suggest that the model could accurately describe different stages of sandstone' s creep deformation.