富水软岩的蠕变特性实验及非线性剪切蠕变模型研究

富水软岩巷道变形速度快,变形量大,巷道支护困难,建立描述该类软岩特性的流变模型是解决该问题的关键。通过不同含水率软岩的直剪蠕变试验表明:在同一剪应力水平下,随着含水率的上升,软岩瞬时弹性模量、极限变形模量和黏滞系数将下降,蠕变速率先增大后减小,加速蠕变的破坏时间缩短;在同一含水率条件下,随着剪切应力的增加,软岩瞬时剪切位移量、蠕变变形量和衰减蠕变段的曲率半径都逐渐增大。依据含水软岩蠕变的非线性特征,建立了能够描述含水软岩蠕变特性的非线性剪切流变模型,基于BFGS算法和通用全局优化法对模型参数进行识别,识别结果与试验曲线吻合较好,表明所建模型的正确性和合理性,该成果可为深部复杂地质力学环境下的富水软岩巷道稳定性研究提供参考。

Study of nonlinear shear creep model and creep property experiment of water-rich soft rock

Water-rich soft rock roadway with fast deformation speed,large deformation and support difficulty,the key for this issue is to establish a rheological model describing the characteristics.Through shear creep test of soft rock with different moisture content,the experimental results show that under the same shear stress level the instantaneous elastic modulus,the ultimate deformation modulus and the coefficient of viscosity of soft rock decreases,the creep rate increases first and then decreases,the destruction time of accelerated creep is shortened with the increase of moisture content；With the increase of shear stress,the instantaneous shear displacement,creep deformation and the radius of curvature of the attenuation creep stage increase gradually under the same moisture content.According to the nonlinear characteristics of water-rich soft rock creep,a nonlinear shear rheological model is established to describe the creep characteristics of water-rich soft rock,and model parameters are identificated based on the BFGS algorithm and universal global optimization method,the identification results agree well with the experimental curves,which show that the model is correct and reasonable.It is very important significance for rich-water soft rock roadway stability research in the deep and complex geological mechanics environment.