Abstract:

The uniaxial different frequency cyclic loadings and unloading tests on biotite granite comes from the Changjiang of Hainan nuclear power first-stage construction major factory district are done on the RMT-150B multi-function automatic rigid rock servo material testing machine. The law between cyclic frequency and dynamic stress- dynamic strain hysteretic curve, dynamic elastic modulus and damping ratio are researched. Then the microtest (SEM) is carried out to study its fractography morphology and microstructure characteristics of failure surface under different frequency cyclic loadings. The results show that the curves of strain and stress for loading and unloading are not superposition under cyclic loading, but hysteretic loops. When cyclic frequency changes between 0.01 Hz and 1.0 Hz, the granite hysteretic loop area, dynamic elastic modulus and damping ratio are increased with frequency increaseing. Based on the testing analysis of microscopic digital image, there are more total number, larger area and fractal dimension of micro-cracks on rock fracture under higher frequency cyclic loading. Mesomechanical damgee mechanism of rock failure under different frequency cyclic loadings is given. The research result offers great reference value to seismic response analysis and site safety evaluation of the nuclear power factory in Changjiang.

Key words: cyclic loading, dynamic elastic modulus, damping ratio, scanning electron microscope(SEM), fractography morphology