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Abstract Uniaxial cyclic loading and unloading experiments for coal samples were performed using electro- hydraulic servo testing machine in order to obtain the relationship between the hysteresis loop and elastoplastic strain energy under cyclic loading and unloading for identifying the burst tendency of coal. The stress-strain curves，the curves of loading cycles against the loop area of hysteresis and the relationship between the elastic strain energy and the loop area of hysteresis were analyzed. The loop area of hysteresis and the elastic strain energy were found to be positively correlated with the circle numbers. The hysteresis loop occurred in the compression phase of the cyclic loading and unloading. When the coal sample was approaching the failure，the irreversible plastic deformation achieved the maximum value. The plastic energy of each cycle was found to be the dissipated energy of the newly generated cracks. The dissipated energy(hysteresis loop area) was not subtracted in calculating the elastic energy index in the previous methods，which led to smaller values. The index formula was thus modified for better predicting the burst tendency of coal.
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Received: 28 April 2014
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2014, Vol. 33 
