循环荷载下饱和岩石的滞后和衰减

HYSTERESIS AND ATTENUATION OF SATURATED ROCKS UNDER CYCLIC LOADING

通过对饱和砂岩和大理岩的循环荷载实验 ,分析了饱和岩石在循环荷载下的应力 -应变滞后回线、瞬时杨氏模量、泊松比的“X”形变化曲线 ,以及杨氏模量随应变振幅的增加而减少等滞后现象 ,并分析了施加外力的应变振幅对衰减的影响 ,认为岩石在循环荷载作用下的衰减与应变振幅成正比 ,提出的衰减b值反映了岩石在循环荷载作用下衰减的程度 .岩石的衰减和滞后存在密切的关系 ,通过饱和岩石的宏观行为 ,探讨了饱和岩石在循环荷载下的滞后和衰减现象的微观机理 ,认为孔隙流体流动在岩石的滞后和衰减中起着重要作用 。

We analyze hysteresis phenomena such as stress-strain loop, 'X' shape of instantaneous modulus and Poisson's ratio, and effect of strain amplitude on attenuation of saturated rocks under cyclic loading by experiments of fluid saturated sandstones and marbles. We think that the attenuation of a rock is in proportion to the strain amplitude of the applied cyclic loading, and the b value of attenuation is a measurement to a saturated rock's attenuation under cyclic loading. We discuss the possible micro mechanisms of attenuation and hysteresis at low frequencies by the macro behavior of saturated rocks in uniaxial stress cycling tests. The flow of porous fluid may play an important role in attenuation and hysteresis of a porous rock, and both the grain contact adhesion and stick-slip friction might be the causes of a porous saturated rock's hysteresis and attenuation in high stress and low frequency cycling tests.