Review and prospect of directional hydraulic fracturing rock breaking technology in underground coal mine

To address the application limitations of traditional weakening techniques under complex geological conditions such as hard coal mine roofs, directional hydraulic fracturing (DHF) technology has become a key technical measure to ensure safety production by virtue of its core advantages of directional rock breaking. This paper systematically reviews the research status and development trends of underground DHF technology in underground coal mines, focusing on an analysis of the three key dimensions: directional fracturing methods, processes, and equipment. Regarding fracturing methods, three mainstream technologies based on manual slotting, linear arrangement drilling, and high-pressure water jet slotting have been sorted out. The paper compares their principles, advantages, and applicable scenarios, pointing out that a linear synergistic fracturing method using multiple fracturing holes with high-pressure water jet slotting demonstrates both precision and scalability, making it the most promising technological path at present. For fracturing processes, it elaborates on the standardized progress of the four core procedures: drilling construction, pre-treatment, high-pressure water injection, and effect verification, and analyzes the key bottlenecks in process optimization under complex geological conditions. In terms of fracturing equipment, technical characteristics and existing issues of drilling, slotting, high-pressure water injection, and monitoring devices are summarized. Aligning the development trends of mining engineering technology, the paper proposes that future directional hydraulic technology will evolve towards intelligent directional fracturing, multi-field coupled fracturing, and miniaturized precision fracturing. At the process level, it will develop towards integrated efficiency, adaptive dynamics, and green low-carbonization, while equipment will focus on breakthroughs in intelligent automation, high efficiency and reliability, and miniaturization and integration. These research results provide a reference for theoretical study, equipment development, and engineering applications of underground DHF technology, contributing to safe, efficient, and sustainable coal mining practices.