花岗岩蠕变特性及分数阶黏弹塑性模型研究

为了解花岗岩蠕变特性，采用全自动岩石三轴伺服仪对其开展试验研究，在常规三轴压缩试验基础上进行多级加载蠕变试验，系统分析花岗岩蠕变过程中整体蠕变规律和同围压不同应力水平下的轴向及环向蠕变变形量、蠕变速率随时间的变化规律。基于分数阶微积分算子及损伤力学理论，在Scott Blair黏壶基础上，考虑蠕变参数的非定常性，建立花岗岩黏弹塑性蠕变本构模型，并推导出其在恒应力情况下的三维黏弹塑性蠕变本构模型。结合花岗岩室内多级加载蠕变试验结果，采用Quasi Newton（BFGS）法对三维蠕变模型参数反演。结果表明，提出的模型与试验数据拟合较好并克服Nishihara模型不能描述蠕变非线性加速特征的不足，能够很好地反映花岗岩三阶段蠕变过程。

Study on creep characteristics and fractional-order visco-elastoplastic model of granite

In order to understand the creep characteristics of granite,a full-automatic rock triaxial servo was used to carry out the experimental research on it.Based on the conventional triaxial compression test,the multi-stage loading creep tests were carried out.The overall creep laws of granite during the creep process were analyzed systematically,as well as the variation laws of axial and circumferential creep deformation amount and creep rate with time under different stress levels with the same confining pressure.Based on the fractional-order calculus operator and the damage mechanics theory,a visco-elastoplastic creep constitutive model of granite was established considering the non-steadyness of creep parameters based on the Scott-Blair stick pot,and its three-dimensional visco-elastoplastic creep constitutive model under the constant stress was deduced.Combined with the results of indoor multi-stage creep tests of granite,the parameters inversion of three-dimensional creep model was conducted by using the Quasi-Newton(BFGS) method.The results showed that the model proposed in this paper fitted well with the test data,and it overcame the shortcoming of Nishihara model which couldn’t describe the nonlinear acceleration characteristics of creep,so it can reflect the three-stage creep process of granite well.