细砂岩阶段蠕应变特征与粘滞性试验研究

对细砂岩试样进行单轴短时加卸载蠕变试验,得到轴向和径向蠕变试验曲线。对轴向和径向蠕变第Ⅰ、Ⅱ阶段的试验曲线分别进行Kelvin-Voigt模型和Burgers模型拟合,得到粘滞系数。粘滞系数-加载应力关系普遍符合扩展的正弦衰减(阻尼)波形函数,表明岩石的粘滞系数是变量,岩石材料的蠕变过程本质为非定常蠕变。细砂岩发生的总蠕应变平均占瞬态应变值的比例较低,其总体蠕变特性不明显,但稳态阶段的径向蠕应变率平均值是轴向蠕应变率平均值的3.6倍。细砂岩初期蠕应变量及稳态阶段蠕应变量随加载应力水平提高而增加,证明其粘性流动度呈递增趋势。

PHASE DEFORMATION AND VISCOUS PROPERTIES IN CREEP TEST FOR FINE SANDSTONE SPECIMEN

Axial and radical creep test curves have been determined by uniaxial short-term creep test with loading and unloading on fine sandstone specimen.Kelvin-Voigt model and Burgers model are used to fit Ⅰ and Ⅱ phases of axial and radical creep test curves respectively and their viscous coefficients have been determined.Relationships between viscous coefficient and loading level may generally answer for developing sine decay / damping waveform function,which presents that viscous coefficient may be a typical variable and creep states of rock like materials are all not stationary.The proportionality of whole creep strain to instantaneous strain states creep is lower,which states creep properties of fine sandstone are not strong.However,average creep strain in steady phase of radical creep test is 3.6 times of that of axial creep test.Initial and steady creep strains are increased with higher loading levels,which can validate that viscous fluxion of fine sandstone will increase by degrees.