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采用自行设计加工的岩石拉伸试验装置,对砂岩进行了直接拉伸蠕变试验。结果表明:拉伸试验中蠕变量与总应变的比值明显高于压缩试验中相应值,表明岩石拉伸蠕变变形能力高于岩石单轴压缩蠕变。分析等时应力-应变曲线直线段斜率变化规律,得到Kelvin体弹性模量随时间变化的表达式,将其代入Kelvin模型中,得到一个改进的非线性广义Kelvin模型,并通过串联的方式,将之与一个能反映非线性加速蠕变特征的黏塑性体联结,组成一个新的非线性蠕变模型。利用非线性曲线拟合软件1st Opt,对试验曲线进行拟合,对模型参数进行辨识,对比试验曲线和拟合曲线,二者能较好地吻合,验证了模型的适用性。
A self-designed rock tensile test device was used to test the direct tensile creep of sandstone. The results show that the ratio of creep quantity to total strain in tensile test is obviously higher than that in compression test, which shows that the tensile creep deformation capacity of rock is higher than uniaxial compression creep of rock. The change of the slope of the straight line of the isochronal stress-strain curve is analyzed to obtain the expression of Kelvin’s elastic modulus with time. The Kelvin model is substituted into the Kelvin model to obtain an improved nonlinear generalized Kelvin model. By using the tandem method, With a non-linear accelerating creep characteristics of viscoplastic body joined to form a new nonlinear creep model. Using the first curve fitting software, 1st Opt, the experimental curves were fitted, the model parameters were identified, and the experimental curves and fitting curves were compared. The two were in good agreement and the applicability of the model was verified.