基于煤体三轴蠕变试验的非线性伯格斯模型

A nonlinear Burgers model based on triaxial creep test of coal

为解决传统伯格斯模型无法描述煤体加速蠕变的缺陷,利用RLW-500G煤岩三轴蠕变-渗流试验系统对原煤试样开展三轴压缩蠕变试验,分析了不同应力水平下煤样轴向应变随时间的变化规律。针对煤样加速蠕变过程中应变加速度与时间呈正比的关系,利用一个非线性黏-弹-塑性体来表示煤体加速蠕变特征,将其与伯格斯体进行串联得到一个改进的非线性伯格斯模型,推导得到该模型在三维状态下的蠕变方程表达式。利用原煤三轴压缩蠕变试验数据,采用模型辨识的方法对改进的非线性伯格斯模型进行验证,结果表明:拟合曲线与试验结果高度吻合,相关系数平方R^2均高于0.98,能够较好地反映出煤样非衰减蠕变过程中3个阶段的变化特征,拟合结果表明改进的非线性伯格斯模型具有较高适用性及优越性。

As the traditional Burgers model can not describe the accelerated creep of coal,a series of triaxial compression creep test of raw coal was conducted using RLW-500 G coal-rock triaxial creep-seepage test system to analyze the variation of the axial strain of coal with time under different stress levels.In view of the direct ratio of strain acceleration to time in accelerated creep process of coal sample,a nonlinear viscous-elastic-plastic body was used to represent the accelerating creep characteristics of coal,and then an improved nonlinear Burgers model was obtained by connecting this viscous-elastic-plastic body with Burgers body in series.A creep equation expression was also deduced of this improved model in three-dimensional state.Finally the improved model was verified by model identification method based on the data of triaxial compression creep test of raw coal.The results show that the fitting curves are in good agreement with the experimental data,and the correlation coefficient square R^2 are higher than 0.98,which can accurately reflect the change characteristics of three stages in non-decay creep process of coal specimens.The fitting results indicate that the improved nonlinear Burgers model possesses higher applicability and superiority.