Abstract：The fatigue tests of gypsum rock were conducted using the dynamic test system MTS 815，acoustic emission system and environmental scanning electron microscope to investigate the impact of cyclic loading on the fatigue damage characteristics of gypsum rock. The shapes of cyclic stress-strain curves of gypsum rock are different from ones of other rocks. The loading curves can be divided into a nearly linear segment with elastic characteristics and a plastic characteristics segment with depressed shapes，which show that the strains lag behind the stresses. The unloading curves exhibit largely the elastic characteristics as the curve shapes are approximately linear. The cyclic loading conditions have obvious influence on the fatigue damage properties of gypsum rock. The damage process and the macroscopic failure characteristics were revealed from the AE information and microstructure characteristics. Under the higher stress level，the larger stress upper limit and the lower loading frequency，the cyclic stress-strain curves are sparser with the larger areas of hysteretic loop in each cycle and the more AE information occur with higher AE rates. In this case，the fatigue damage rate is higher，the plastic strains are larger and the more microstructures are broken in each cycle.
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2017, Vol. 36 
