砂岩卸围压蠕变特性及非定常蠕变模型

Creep characteristics and unsteady creep model of sandstone under unloading confining pressure

为了研究在不同围压卸载条件下,砂岩蠕变变形的变化规律以及蠕变参数劣化规律,采用TAW-2000试验机对砂岩进行室内分级卸围压蠕变试验研究,然后结合损伤力学理论将蠕变参数非定常化,建立非定常参数西原蠕变模型,最终将试验数据与模型曲线进行对比验证。试验结果表明:对砂岩进行不同初始轴向应力的卸围压试验,岩石的蠕变泊松比与蠕变变形一样,都具有衰减、稳定和加速三个阶段,蠕变泊松比是一个时间的函数,在加载过程中蠕变泊松比都超过常规状态下的值,甚至超过1;建立非定常模型与试验数据具有良好拟合度,它不仅准确地反映了衰减和稳定蠕变阶段蠕变特性,也克服了传统西原体难以描述加速蠕变的缺点。

In order to study the creep deformation, time variation law and creep parameter deterioration law of sandstone under different confining pressure unloading conditions, the test of sandstone staged unloading confining creep was carried out by using TAW-2000 test machine.Then the creep parameters were denormalized by the theory of damage mechanics, and the unsteady parameter Nishihara creep model was established.Finally, the test data was compared with the model curve.The test results showed that the sandstone was subjected to different unloading confining pressure tests of initial axial stress.The creep Poisson's ratio of rock had the same three stages of attenuation, stability and acceleration as creep deformation.Creep Poisson's ratio was a function of time. During the loading process, the creep Poisson's ratio exceeded the value in the normal state, and even exceeded 1.The establishment of the unsteady model had good fitting degree with the experimental data. It accurately reflected the creep characteristics of the attenuation and stable creep stage.The difficulty of describing the accelerated creep of traditional Nishihara model has been overcome.It had practical guiding significance.