Abstract: The failure damage of granite under cyclic load is caused by the propagation and coalescent of cracks at mesoscale, so it is helpful to understand the mechanical behaviours of rock by quantitatively investigating on meso-damage of granite. The uniaxial cyclic fatigue tests on granite coming from Changjiang of Hainan province are done on the RMT-150B multi-function automatic rigid rock servo material testing machine. Stress amplitude of 10 MPa and sine wave cyclic loads with five different frequencies of 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1 Hz are adopted as dynamic disturbance. A great deal of mesostructural images of Changjiang granite in Hainan province have been obtained by means of scanning electron microscopy(SEM). The mesostructural images of marble are processed by regional growing theory based on image processing technique. The meso-damage information of granite microcracks is obtained from SEM images. Quantitative analysis of meso-damage characteristics under cyclic fatigue load is made from angle, length, width and area. It is shown that with the frequency of cyclic load increasing, the dispersion of microcrack growth azimuth value increases and the average of microcrack growth azimuth value fluctuates in the range. The development of microcrack length is fast; but only when the frequency is 1 Hz, the microcrack width begins to develop and the method of energy dissipation changes.

Key words: different frequencies, cyclic load, microcrack, quantification