Deformation properties of rock mass with intermittent cracks under cyclic loading

The fatigue properties of the rock mass with intermittent cracks under blasting and earthquake are the most basic problems in rock mechanics.The force-displacement curves were tested under uni-axial cyclic loading in the experiment and the specimens were made of sandstone-like modeling materials containing two or three pre-existing cracks with different geometry distributions.In virtue of the analysis of irreversible deformation and total deformation with cyclic number,the fatigue deformation properties of the cracked specimens were discussed.Then,some influential factors,such as loading frequency,load level and geometrical position of cracks on fatigue properties of the cracked samples were analyzed and discussed.It was indicated that the development of fatigue deformation of samples with intermittent cracks could be divided the into three stages: the initial deformation stage,the constant deformation rate stage and the accelerative deformation stage which were same as the intact rock and block-jointed rock;the fatigue deformation limit corresponding to the maximum cyclic load was equal to that of post-peak locus of static complete force-displacement curve;and the fatigue deformation was controlled not only by the loading frequency and the load level,but also by the geometrical position of intermittent cracks.