岩石非定常Burgers蠕变模型及其参数识别

针对岩石蠕变的非线性特征，提出了一种非线性黏壶元件，并分别替换Burgers模型中的两个线性黏壶元件，从而建立了一种非定常参数Burgers模型。推导了非定常Burgers模型的一维蠕变方程，分析模型参数λ₁与λ₂取值范围对蠕变方程的影响，从理论上确定了非定常模型能够描述蠕变的3个阶段。在此基础上，将非定常Burgers模型的蠕变方程推广至三维应力状态下，并基于Levenberg-Marquardt算法对向家坝岩石的三轴压缩蠕变试验曲线进行拟合及参数识别。通过对比定常与非定常Burgers模型的拟合曲线与相关系数，可以发现非定常Burgers模型拟合效果更好，且能够准确描述包括加速蠕变在内的岩石三阶段蠕变特性，验证了所构建非线性模型的适用性与合理性。

NON-STATIONARY BURGERS CREEP MODEL OF ROCK AND ITS PARAMETER IDENTIFICATION

In view of the nonlinear characteristics of rock creep, a nonlinear viscous component is proposed to replace the two linear viscous components in the Burgers model. Accordingly, a non-stationary Burgers model is established. The one-dimensional creep equation of the non-stationary Burgers model is deduced and the concomitant influence of the range of parameters λ₁ and λ₂ in the model is analyzed. Then, the non-stationary model is theoretically determined to describe the three stages of creep. On this basis, the creep equation of non-stationary Burgers model is extended to three-dimensional stress state. Triaxial compression creep test curve of rock in Xiangjiaba is fitted and its parameters are identified based on the Levenberg-Marquardt algorithm. By comparing the fitted curve and correlation coefficient between stationary and non-stationary Burgers models, it can be found that the fitted results of the non-stationary Burgers model are much better and can accurately describe the creep features in three stages including the accelerated creep status. The applicability and rationality of the established nonlinear model are verified.