General shapes and criterion for surrounding rock mass plastic zone of round roadway

Considering the plastic zone shape of roadway surrounding rock determines the failure mode and the damage degree of surrounding rock,the evolution law for general shape of circular roadway plastic zone is comprehensively re- searched based on the plastic zone boundary implicit equation. And the results show that giving a certain kind of rock lithology,the surrounding rock plastic zone of circular roadway under a variety of confining pressure shows three theo- retical shapes:round,oval and butterfly. Besides,the mathematical and mechanical meaning of the three shapes are found and the criteria of different shapes is derived through theoretical analysis. The concept of shape coefficient of plastic zone is put forward,and the formula of shape coefficient is derived,whose magnitude can represent the morpho- logical characteristics of the plastic zone. With numerical simulation FLAC3D ,the correctness of the theoretical calcula- tion is verified. The research results can be used as theory basis of engineering practice for the roadway stability analy- sis,the supporting design,the prevention and control of roof fall disaster,the prediction and prevention of rock burst, the prediction and prevention of coal and gas outburst,etc.