循环荷载下岩石变形参数和阻尼参数探讨

 对取自一拟建核电站地基的细砂岩，在MTS815 Flex Test GT岩石力学试验系统上进行低周循环荷载试验，研究循环荷载下细砂岩的纵横向变形特征，探讨循环荷载周次及动应力幅值对细砂岩动弹性模量、动泊松比、阻尼比和阻尼系数的影响，及与其相互关系。结果表明，相同应力下纵向应变高于横向应变；低幅值应力下，随循环荷载周次增加，纵向应变增量高于横向应变增量，但高幅值应力下则相反；横向应变滞回环的卸载阶段应力–应变曲线与纵向应变滞回环的加载段和卸载段均表现出向下突出的变化特征，但横向应变滞回环的加载段则相反；随动应力幅值增加，细砂岩动弹性模量和动泊松比分别呈抛物线递增和线性递增，阻尼比和阻尼系数均按幂函数律递减，由第16周次动应力滞回环得到的阻尼参数可表征测试岩石的阻尼特征；阻尼比和阻尼系数均随循环荷载周次增加线性递增，对应低幅值动应力下的增量大于高幅值动应力下的增量。

DISCUSSION ON DEFORMATION AND DAMPING PARAMETERS OF ROCK UNDER CYCLIC LOADING

The uniaxial compression cyclic loading and unloading tests on fine sandstone comes from the foundation rock of a nuclear power station are carried out on the MTS 815 Flex Test GT rock mechanics test system.The longitudinal and transverse deformation characteristics of fine sandstone are studied under cyclic loading;and the effects of cyclic loading numbers and dynamic stress amplitudes on dynamic elastic modulus,dynamic Poisson s ratios,damping ratios and damping coefficients are discussed.The results indicate that the longitudinal strain is larger than the transverse strain for the same stress.With the cyclic numbers increasing,the increment of longitudinal strain is larger than that of transverse strain under low amplitude stress;but it is reverse under high amplitude stress.The changing characteristics of stress-strain curves for the unloading process of transverse strain hysteresis loops and the loading and unloading processes of longitudinal strain hysteresis loops are all outstanding down,while the changing characteristics of loading process for transverse strain hysteretic loops are reverse.With the dynamic stress amplitude increasing,dynamic elastic modulus and dynamic Poisson s ratio increase on a parabola and linearly,respectively,while the damping ratios and damping coefficients decrease by power function law.The damping parameters gained by the sixteenth hysteresis loops can completely denote the damping characteristic of the testing rock.With the cyclic numbers increasing,damping ratio and damping coefficient both increase linearly;and the increment under low amplitude stress is larger than that under high amplitude stress.