循环荷载作用下花岗岩疲劳力学性质及其本构模型

 循环荷载作用下岩石力学性质研究对完善岩石力学基本理论和指导相关工程建设具有重要意义。通过花岗岩三轴循环荷载试验，系统研究花岗岩疲劳力学特性，提出花岗岩疲劳力学模型。研究结果表明：(1) 岩石残余应变和变形模量与循环次数之间关系与岩石体积变形状态相关；(2) 在应力–应变全空间内，花岗岩疲劳性质分为3个区域，不同区域内微观机制不同；(3) 岩石疲劳破坏门槛值应为剪缩和剪胀区域分界点对应的峰值偏应力；(4) 循环荷载作用下岩石疲劳势有别于单调加载时塑性势，循环荷载作用下岩石表现出比单调加载时更强的抵抗体积变形能力；(5) 提出基于内变量理论的岩石疲劳本构模型，试验数据与模拟预测对比显示模型较好地反映出岩石疲劳力学性质。

FATIGUE MECHANICAL BEHAVIOR OF GRANITE SUBJECTED TO CYCLIC LOAD AND ITS CONSTITUTIVE MODEL

It is important to investigate the mechanical behavior of rock subjected to cyclic loading for both the basic theory of rock mechanics and the construction of geotechnical facilities.A series of triaxial compression tests under cyclic loading were performed to study the fatigue behavior of granite;and hereby a constitutive model was proposed to describe its fatigue behavior.In the tests,the following conclusions can be drawn.(1) The relation between residual strain and cycle number is influenced by the volumetric deformation behavior of granite,and so the relation between deformation modulus and cycle number is.(2) The fatigue behavior of granite could be divided into three domains in the stress-strain space,and the micro mechanism in one domain is different from that in another domain.(3) The threshold for fatigue failure of granite could be the peak deviatoric stress corresponding to the point transferring from volumetric contraction to volumetric dilation.(4) The potential of fatigue deformation is different from that of monotonic plastic deformation,while the granite exhibits a higher resistance to volumetric deformation under cyclic loading than that under monotonic plastic loading.(5) An internal variable fatigue constitutive model was proposed for the rock;and the fact that the predicted fatigue behavior is consistent with that observed in tests,so as to show that the constitutive model is capable of describing the fatigue behavior of rocks.