Research progress on permeability improvement mechanisms and technologies of coalbed deep-hole cumulative blasting

Coalbed gas extraction is an important means of exploiting and utilizing gas resources, as well as a means of preventing coal mine disasters. In view of the low gas extraction rate from coalbeds with high gas content and low permeability, a method of improving permeability through deep-hole cumulative blasting is applied to develop initial directional fractures using a jet flow. Under the action of the blasting stress wave and detonation gas wedge, the fractures extend over a large range within the coal, thereby improving coalbed permeability. This study focuses on the criteria of cumulative blasting-induced coalbed fracturing based on a literature review of the penetration effect of cumulative blasting. On this basis, we summarize the coal fracturing zone, crack extension process, and the key technologies of charging and hole sealing for cumulative blasting. In addition, the latest research progress in the optimization of field test drilling and blasting parameters for cumulative blasting is introduced. Research findings indicate that the permeability improvement mechanism of cumulative blasting could be further enhanced, and the technology and technical equipment are in urgent need of improvement. Finally, development trends in the cumulative blasting permeability improvement technique are identified.