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| Experimental study on mechanical and damage characteristics of coal under cyclic true triaxial loading |
| DUAN Minke1，JIANG Changbao2，GUO Xianwei3，YANG Ke1，ZHANG Xiangyang1，MA Haifeng1 |
| (1. State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines，Anhui University of Science and Technology，Huainan，Anhui 232001，China；2. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400030，China；3. Jining No.3 Mine，Yanzhou Coal Mining Corporation Ltd.，Jining，Shandong 272169，China) |
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Abstract To study the influence of true triaxial cyclic disturbance stresses on the mechanical characteristics of coal in the process of mining and excavation，the coal mechanical experiment under the intermediate principal stress() of tiered cycle is carried out based on GCTS true triaxial mechanical experiment system，and the influence of on deformation，energy consumption and damage characteristics of coal is analyzed. The results show that the effect of tiered cyclic on and is greater than that on . With increasing ，both and decrease significantly. Cyclic loading or unloading of can cause instability and failure of coal. When σ3 is small，coal tends to be destroyed in the process of unloading to close to ，and when is large，coal tends to be destroyed in the process of loading close to . However，the approximation rate of corresponding to failure is similar，all around 70%. The loading or unloading of has equivalent effect on the residual deformation and even failure of coal. With increasing the amplitude of tiered cyclic ，the total dissipation energy of coal increases exponentially，and the damage variable of coal presents an obvious S-type change trend of deceleration, acceleration and re-deceleration. The threshold value of the average safety damage variable of coal and rock is 0.9 in the process of tiered cyclic.
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2021, Vol. 40 
