###### Abstract  
To solve the bottleneck problem of low deep coal seam permeability and difficult coalbed methane (CBM) mining. Combining hydraulic splitting technology and directional drilling technology, a directional hydraulic splitting enhancement method of deep CBM mining was proposed. The selection equation for the directional hydraulic splitting of deep coalbed was constructed. The numerical simulation reveals the variation in coal fractures around different split angles. The split angle under the maximum coal damage effect was obtained. It was found that the combined effect of the double crack damage disturbance region led to reciprocal stress fluctuations during crack development and, eventually, the formation of a zigzag fracture. The larger the splitting angle, the larger the fissure development length and the larger the coal-damaged area. A double crack takes 25% less time to complete propagation than a single crack. When the splitting angle is 90\({}^{\circ}\), the disturbed area occupies 2/3 of the area around the borehole, and the overall fracturing effect is the best. In the application process, the new directional hydraulic splitting technology can increase CBM mining by 5.08%, greatly improve CBM mining efficiency, and reduce the coal mining risk, which is of great significance to the project. directional splitting; damage region; coalbed methane mining; coalbed permeability enhancement  
29 October 2022  
formed by a single liquid nitrogen injection process [15; 16]. Thus, finding the optimal combination of cyclic/pulsating liquid nitrogen injection parameters that are safe, efficient, and economical is necessary. At the same time, the crack scale produced by using low-temperature liquid nitrogen is small, and the penetration has some limitations [17; 18]. The CBM blasting method has certain safety problems in fracturing the coalbed, which may cause mine vibration, workforce collapse, and pose a hidden risk to the safety of workers. Hydraulic fracturing may cause stress changes in the fault during the process, resulting in the \"jumping\" of the fault and earthquake [19; 20]. In addition, although the above methods improve the permeability of the coalbed and increase the extraction efficiency of CBM, liquid tends to flow out from the crack region of the coalbed when they encounter the crack region [21]. As a result, the above methods cannot reach the deep part of the coalbed, thereby being less effective in increasing the recovery of deep CBM. Moreover, the above methods have low working efficiency, high construction costs, and insufficient crushing accuracy. When the traditional technology is limited, hydraulic splitting technology shows obvious advantages. Hydraulic splitting technology is able to split the coal directionally and rapidly through rigid crushing, causing directional displacement of the coal and forming longer cracks. Moreover, hydraulic splitting technology requires very low geological conditions. It is well-suited to fracturing and increasing the coalbed permeability under various conditions. Meanwhile, hydraulic splitting technology can be applied to prefabricated fractures before directional water injection fracturing, allowing the fractures to propagate along the prefabricated fractures to form directional fracturing to increase permeability. The joint action of multiple cracks is required to increase the range of the disturbance area as much as possible. Through technical updating, it is now possible to install two rows of outward extending split pistons in the unit. However, the damaging effect of coal under different split angles is not yet clear. Therefore, to achieve the best crushing effect of coal, it is urgent to conduct research on the mechanism of coal breaking and permeability enhancement under the combined action of double cracks. Based on the crack propagation criterion, the selection equation of the deep coal seam directional hydraulic splitting cleavage angle was derived to solve the above problems.