## 4 Discussion  
With the increase in the coal mining depth, the coal seam stress increases, the coal permeability decreases, and coalbed methane extraction is difficult. In order to solve this problem, experts have investigated different methods to increase coal seam permeability and improve the efficiency of coalbed methane extraction. Many methods include liquid nitrogen freezing and cracking, gas blasting technology, hydraulic fracturing technology, and so on. These methods all show some effects, but they also have some defects. The freezing technology of liquid nitrogen is limited, the gas blasting technology is dangerous, and the hydraulic fracturing technology is easily affected by geological conditions.  
When the traditional technology is limited, the advantages of hydraulic splitting technology are clear. In the face of the uncontrollability of liquid nitrogen freezing-cracking technology and small cracking, hydraulic cracking technology shows the advantages  
Figure 14: Comparison of the extraction effects of different methods at the same depth.  
of long macroscopic crack lengths and the controllable expansion direction of cracks. Liquid nitrogen cannot be recycled after use, and the cost is high. The hydraulic splitting technology device can be reused many times to reduce the construction cost. In addition, although the effect of the common gas blasting is good, the range is large and easily causes working face vibration; mine environments are complex, the increase in vibration means that they may cause collapse and other accidents, where workers may be injured. Hydraulic splitting technology is a static mining technology, which can ensure the safety of underground operations. In addition, the hydraulic measures should improve the extraction efficiency and reduce the dust concentration of coal seam mining. However, when encountered in a fault, there may be running water and other phenomena, resulting in a poor effect. In the face of this situation, hydraulic splitting technology has very low requirements on geological conditions, which can be well-suited to coal seam cracking under various conditions. At the same time, the liquid pressure produced by the device can reach 40 MPa, which shows a good effect on the coal seam with higher hardness. Of course, the device can also be applied to the prefabricated cracks before the directional hydraulic pressure, which extend along the prefabricated cracks to form the directional cracks.  
According to the present situation in deep CBM mining, the following was proposed. The directional hydraulic splitting of a deep coal seam was constructed. The expansion law of the cracks from a hydraulic splitting device on the coal around the drilling holes was simulated. The change characteristics of the coal rock disturbance region under different splitting angles were analyzed. Compared with the work of previous scholars, the work of this paper is more targeted. According to the actual operation situation, we simulated the range of coal rock disturbance under different splitting angles, and this research provides some guidance for the deep directional hydraulic penetration project of coal mining. In fact, the research work in this paper is based on the high hardness of the coal body, and the coal-crushing characteristics of the softer coal layer need to be further discussed.