Microseismic Behavior during Mining of the Working Face under Blasting Presplitting of a Hard Roof.

Blasting presplitting is an effective method for preventing rock bursts in thick hard roofs. In this study, two adjacent working faces in the No. 10 mining area of the Jining No. 2 coal mine were considered as case studies, and the conditions of the working face and the construction parameters for roof blasting presplitting were introduced. The microseismic characteristics of the 2 working faces during the mining period were analyzed, and 10 indices for evaluating the microseismic characteristics of the working faces were proposed. Accordingly, the influence of blasting presplitting on the microseismic characteristics of the surrounding rock was evaluated. The results showed that the frequency of microseismic events changed with the mining stage of the working face. After the roof of the 103down03 working face was presplit, the average energy of microseismic events, maximum energy of microseismic events, and proportion of high-energy events all decreased significantly. The average height of the source decreased from 31.08 m above the coal seam to 8.78 m, and the average strike location of the source decreased from 102 to 32 m in front of the working face. After presplitting, the roof gradually changed from large-scale and high-energy fractures to small-scale and low-energy fractures. After blasting presplitting, the energy accumulated in the roof was released through the collapse of the roof in the goaf, which improved the burst risk in the coal and roadway in front of the working face, thus ensuring the safety of underground construction personnel and equipment. [ABSTRACT FROM AUTHOR]