闪长玢岩蠕变试验及黏弹-塑性损伤模型研究

Creep test and viscoelastic plastic damage model of diorite porphyrite

为探究闪长玢岩蠕变特性,开展了分级加载和循环加卸载三轴蠕变试验,研究了闪长玢岩的变形及长期强度特征,并基于试验结果,建立了能够描述闪长玢岩黏弹-塑性变形的损伤蠕变模型。研究结果表明:随着偏应力水平的增加,轴向变形和侧向变形逐渐增加,体积变形先增加后减小;轴向应变率先降低后基本保持不变,试样破坏时又迅速增加。在同一偏应力水平下,瞬时弹性应变大于瞬时塑性应变,而黏塑性应变大于黏弹性应变。通过稳态速率与应力比关系曲线法,可以得到更加准确、具体的岩石长期强度。基于黏弹性应变曲线特征,建立了考虑黏滞系数随时间和应力衰减的Kelvin模型;将Abel黏壶与塑性滑块元件并联,并引入损伤变量,建立了黏塑性损伤模型,将两者串联得到了闪长玢岩损伤蠕变模型。将试验曲线与模型曲线进行对比拟合,拟合程度较高,验证了模型的合理性。

In order to study the creep characteristics of diorite porphyrite,triaxial creep tests of graded loading and cyclic loading-unloading were carried out to study the deformation and long-term strength characteristics of diorite porphyrite.Based on the test results,a damage creep model which can describe the viscoelastic plastic deformation of diorite porphyrite was established.The results show that with the increase of deviator stress,the axial deformation and lateral deformation increase gradually,and the volume deformation increases first and then decreases.The axial strain decreases first and then remains unchanged,and increases rapidly when the specimen is damaged.At the same deviator stress level,the instantaneous elastic strain is greater than the instantaneous plastic strain,while the viscoplastic strain is greater than the viscoelastic strain.More accurate and specific long-term rock strength can be obtained by the method of the relationship curve between steady state rate and stress ratio.Based on the characteristics of viscoelastic strain curve,a Kelvin model considering the attenuation of viscosity coefficient with time and stress is established.A viscoplastic damage model is established by paralleling Abel clay pot with plastic slider element and introducing damage variable,and a damage creep model of diorite porphyrite is obtained by connecting the two in series.The test curve is compared with the model curve and the fitting degree is high,which verifies the rationality of the model.