循环加卸载下闪长玢岩蠕变特性及损伤本构模型

Creep property and damage constitutive model of dioritic porphyrite under cyclic loading-unloading

  • 摘要: 分级加载压缩蠕变试验未能充分考虑稳定蠕变中的黏塑性应变,故采用三轴循环加卸载压缩蠕变试验来实现岩石的黏弹、塑性应变分离,从而使岩石黏弹、塑性应变在岩石蠕变的各个阶段得以充分考虑。以某水电站闪长玢岩为例,探讨该类岩石蠕变特性。在破坏前,岩石的瞬时弹性应变以及瞬时塑性应变随着偏应力逐级增大呈线性增长;随着偏应力的增加,黏弹性应变和黏塑性应变呈非线性增长。引入一个分数阶Abel黏壶与Kelvin模型串联形成新型黏弹性模型;用分数阶Abel黏壶代替传统的黏塑性模型中的线性牛顿体并基于损伤建立黏塑性损伤模型。然后将新型黏弹性模型和黏塑性损伤模型与瞬时弹性模型和瞬时塑性模型串联组成一个新的岩石蠕变损伤模型。最后将该模型与岩石蠕变曲线进行拟合,从而证明该模型的适用性。

     

    Abstract: The hierarchical loading compression creep test fails to fully consider the viscoplastic strain in a stable creep. Thus, the triaxial cyclic loading compression creep test is adopted to realize the separation of viscoelastic and viscoplastic strain to fully consider the two strains in each stage of the creep. With the development of hydropower project construction in China being moved towards the mountain valley, the geological conditions and engineering environment faced by geotechnical engineering become more complex. Moreover, in the process of geotechnical engineering design, engineering construction, and safe operation, the effect of the rheological, mechanical properties of rock becomes more difficult to ignore. This engineering problem is becoming more significant for the staff involved. Therefore, rheological, mechanical properties of rock have become a very important research content. This study took the diorite porphyry of one hydropower station as an example to discuss the creep characteristics of this type of rock. Before the failure, the instantaneous elastic strain and instantaneous plastic strain increase linearly as the deviator stress gradually increases. With increased deviator stress, the viscoelastic strain and viscoplastic strain exhibit a nonlinear increase. The fractional Abel viscous pot and Kelvin model were introduced to form a new viscoelastic model. The fractional Abel viscous pot was used to replace the linear Newtonian fluid in the traditional viscoplastic model, and a viscoplastic damage model was established based on the damage variables. The new viscoelastic plastic model and viscoplastic damage model were then connected in series with the transient elastic model and transient plastic model to form a new rock creep damage model. Finally, the model is fitted with the rock creep curve to prove the applicability of the model.

     

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