Experimental study on prediction of rock burst risk by multi-parameter indexes of borehole

In order to accurately predict the danger of rock burst, a method for predicting impact risk by monitoring the variation law of drilling parameters such as drill rod thrust, drill rod torque and drill cutting quantity during drilling was proposed. Using self-developed integrated testing device of multi-parameters of borehole, test and analysis of multi-parameters of different coal stress state under laboratory environment, it was found that the drilling rod torque and drilling cutting quantity increased with the increase of the stress of the coal body. As the drilling time increased, the drilling rod thrust firstly increased and then decreased, showed a trough of wave, and then increased and finally decreased. Under the same drilling and drilling tool conditions, in-situ experiment drilling was carried out in mine. The results indicate that with the increase of drilling depth, the change regulation of drilling rod torque and drilling cutting quantity showed a high degree of consistency, before 5 m depth, all of them first increased and then decreased. The thrust of drilling rod is on the rise in 1-4 m, down to the trough of wave at 5 m, then the thrust value rised again, and finally showed a steady trend. The distribution of stress in this area was divided, it could be determined that the stress peak point was approximately at 5 m deep in the hole. And the SPSS data analysis software was used to preliminarily determine that the critical thrust index of the drill rod of this test point was 7.5 kN, the critical index of drilling rod torque was 50 N·m. The research results can provide theoretical basis and engineering guidance for prediction of coal mine dynamic disaster risk such as rock burst.