Rockburst start-up condition influenced by accelerated creep of surrounding rock of circular roadway

Aiming at the creep rockburst phenomenon of roadway with high static load,the effect of accelerated creep of coal-rock in elastic zone on roadway rockburst was studied. Firstly,based on the relationship between the isochro- nous stress-strain curve and the complete stress-strain curve,the time-dependent mechanical parameters of accelerated creep damage of coal-rock were obtained. Then,by analyzing the accelerated creep process and its conditions of coal- rock in elastic zone of roadway,and considering post-peak strength softening of the plastic zone,the stress field of plas- tic zone of the circular tunnel was derived. Based on this,combining with the idea of the criterion of disturbance re- sponse,rockburst start-up mechanism and its critical condition influenced by accelerated creep of surrounding rock were discussed. Finally,the effect of the support force and the secant modulus ratio Mt of the isochronous stress-strain curve were analyzed. The results show that high ground stress,low support force of the primary support and low uniaxi- al long-term strength of the coal provide favorable conditions for emerging accelerated creep of coal-rock in the elastic zone of roadway. Meanwhile,rockburst start-up is formed through the time-dependent strength deterioration caused by accelerated creep of coal-rock in elastic zone. With the higher ground stress of roadway,rockburst start-up can be acti- vated only undergoing small strength deterioration of coal-rock in the elastic zone. In addition,under the influence of accelerated creep,increasing the supporting force can promote to inhibit occurring of rockburst. It means that coal-rock in the elastic zone needs to undergo larger strength deterioration for rockburst start-up with the higher supporting force. Moreover,the peak stress in surrounding rock is lower and the resistance in the plastic zone is larger under this cir- cumstance. Besides,post-peak and pre-peak modulus ratio λ / E0 of coal-rock under uniaxial compression is the non-in- fluencing factor of accelerated creep of coal-rock in the elastic zone of roadway,but it is an important influencing factor for rockburst start-up of the roadway. Namely,the critical ground stress criterion of emerging accelerated creep of coal- rock in the elastic zone is independent of λ / E0 and coal-rock in the elastic zone needs to undergo a greater degree of strength deterioration for rockburst start-up with the smaller value of λ / E0 . Moreover,the core for inhibiting creep rockburst of roadway lies in controlling the elastic zone coal-rock not to reach the condition of emerging accelerated creep.