Determination of critical depth in rockburst mine based on the energy of coal rock dynamic system

In order to calculate the critical depth in a typical rockburst coal mine quantitatively for preventing and controlling rockburst effectively,the types of rockburst mine have been divided into typical rockburst mine and atypical rockburst mine based on the geo-dynamic environment evaluation method.Energy characteristics of coal-rock dynamic system,the relationship between occurrence of rockburst and the system are analyzed by the constructed model of coal-rock dynamic system.Energy characteristics of coal-rock dynamic system in gravity stress field,tectonic stress field,and mining stress field are determined respectively,and the corresponding calcu-lation methods are put forward.Subsequently,the calculation method of the critical depth in typical rockburst coal mine is put forward,and the accuracy of which is validated in three typical coal mines.The results show that the total energy of coal-rock dynamic system is consisted of the energy in self-weight stress field,tectonic stress field and mining stress field.The energy in self-weight stress field is defined as the basic energy,the released energy is the difference between the basic energy and the energy in tectonic stress field or mining stress field.For a typical rockburst mine,the total energy of the coal-rock dynamic system mainly comes from the tectonic stress field,the energy accumulated by the system can support the occurrence of rockburst,which induced by some mining activities.For an atypical rockburst mine,the energy accumulated by the system in tectonic stress field cannot support the occurrence of rockburst,which additional energy is needed.According to the verification results,the calculation method of critical depth in typical rockburst mines,and the calculation method of energy of coal-rock dynamic system are accurate,the accuracy rate can be more than 93%,which could be widely used in forecasting the risk of rockburst.There are many energy supplement factors in coal-rock dynamic system for atypical rockburst mines,such as coal pillar stress,roof movement,etc.,which will be further researched in the future.