硬脆性岩石卸荷流变特性及本构模型研究

依托某在建大型水电站,采用保持轴向应力不变、分级卸围压方式,对硬脆性花岗岩进行蠕变试验,分析了硬脆性岩石的卸荷蠕变变形特性及宏观和微细观破裂形式。结果表明,硬脆性岩石的卸荷流变过程可分为减速蠕变、等速蠕变和加速蠕变三个阶段,并且存在卸荷流变门槛值。岩样屈服前后,轴向应变和侧向应变关系分别符合线性函数关系和对数函数关系。低围压下岩石主要发生沿轴向的张拉性劈裂破坏,高围压下则发生沿斜截面的剪切破坏。基于对蠕变损伤演化的分析,建立了硬脆性岩石非线性粘弹塑性损伤流变模型,以便描述硬脆性岩石不同阶段的蠕变特性。

Study on unloading rheological characteristics of hard brittle rock and its constitutive model

Based on a large hydropower station under construction， a creep test of hard brittle granite is made by keeping the axial stress constant and releasing the confining pressure step by step， and then the unloading creep deformation characteristics and both the macro and micro fracture modes of the hard brittle rock are analyzed. The result shows that the unloading rheological process of the hard brittle rock can be divided into three phases， i.e. primary creep， constant creep and accelerated creep， while the unloading rheological threshold value is there as well. Before and after yielding of the rock sample， the relationships of the axial strain and the lateral strain are in accord with the linear function relation and the logarithm function relation respectively. Under low confining pressure， the tensile splitting failure is mainly taken place axially， meanwhile， the shear failure occurs along oblique section under the high confining pressure. In accordance with the analysis made on the creep damage evolution， a nonlinear visco-elastoplastic damage rheological model for the hard brittle rock is established， so as to describe the creep characteristics of the hard brittle rock in various phases.