Nishihara acceleration model-based experiment of creep characteristics of coal

For conquering limitation that the traditional Nishihara model cannot describe the accelerated creep characteristics of coal body, according to the visco-elastic-plastic flow characteristics of coal in the accelerated creep stage, a nonlinear visco-elastic-plastic model was used to replace the ideal viscoelastic-plastic body in Nishihara model to establish the improved Nishihara acceleration model. And creep equation of the improved model under equal confining pressure triaxial condition was also deduced. Afterwards, the improved accelerated creep model was analyzed by the creep test data of coal specimens in the triaxial creep tests using the method of model identification. The results show that the fitting results are basically consistent with the test data, which can preferably reflect non-decay creep characteristics of coal. In addition, the stability of the improved model was also analyzed, the parameter E₃ has clear physical significance, and E₃ < 0 can be used as the basis for judging creep instability of coal.