岩石单轴拉伸蠕变特性试验研究

Experimental Study on Creep Properties of Rock in Uniaxial Tension

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。

In order to predict the creep response of rock in uniaxial tension,the direct uniaxial tensile creep experiment of sandstone was conducted by the uniaxial direct tension device designed and developpd on our own.Results show that tensile creep curves have a similar shape to compressive creep,but the ratio of tensile creep and the total amount of creep is significantly higher than the correspongding values of compression test. By the variation of deformation modulus in the approximate straight line segments of isochronous stress-strain curves,we can get a expression of Kelvin body viscoelastic modulus varied with time,and put this expression into the modified Kelvin,then a revised modified nonlinear Kelvin was obtained. A new viscoplastic was proposed to describe the accelerated creep characteristics,which was connected with the revised modified nonlinear Kelvin model in series to form a new nonlinear viscoelastoplastic creep model. Based on test result,the optimize anglysis software 1st Opt was choosed to identify the model parameters,which has a quite ideal effect. The test curves are coincident well with the theoretic cruves,which verified the correctness of the model.