## 5 Discussion
In view of this, we must quickly take targeted measures to weaken the strength of a hard roof so as to reduce the adverse effects of a dynamic load on high-stress coal. Figure 17: Principle of dynamic and static combined load inducing rock burst. In the mining process of an extra-thick coal seam, the failure zone of the overburden rock is extensive, and the hanging of a hard roof can reach more than 100 m. However, at present, roof pre-splitting weakening technology is mainly applied in the underground, which is restricted by the underground space, with equipment used for fracturing and drilling lengths. The treatment range is within 50 m and the effect is limited. Therefore, higher requirements are necessary for the control of a hard roof, which needs to be controlled in a larger space. Surface drilling fracturing technology is a kind of stimulation technology commonly used in the development of oil and gas fields. Its mechanism is to pump the fracturing fluid into the reservoir through a hydraulic pump, so that artificial anti-reflection cracks with a certain geometric size and conductivity can be formed in the target layer, thereby improving the extraction efficiency. While ground fracturing and permeability are improved, large-area cracks also weaken the strength of the rock mass. Based on this technical idea, the method of ground fracturing is proposed. Ground fracturing control hard roof technology injects high-pressure liquid into the fracturing position through the fracturing well, promotes the formation of cracks in the rock, weakens the roof, and shortens the breaking span to achieve the prevention and control of rock burst. The ground fracturing high hard rock strata changes the fractures of the rock strata by fracturing the rock strata before it breaks. In this way, when the working face enters the mining stage, the overlying hard roof will collapse in time and effectively with the advancement of the working face. Therefore, as a new type of technology to control rock burst, ground fracturing has good practical significance and popularization significance, as shown in Figure 18.  
Since 2020, the engineering application of ground fracturing to control rock burst and mine earthquake disasters has gradually begun to be applied in China. Different fracturing methods can be selected according to different geological conditions. At present, the rock strata in domestic mining areas are predominantly subjected to horizontal stress. After ground fracture, the main direction of fracture propagation is horizontal. When the overburden rock has a single thick-hard rock strata, accompanied by impact risk or strong mine pressure phenomenon, the horizontal well is used to carry out global fracturing along the advancing direction of the working face, which can effectively avoid the occurrence of dynamic disasters in the stop. In situations where the overburden consists of multiple layers of thick and hard rock strata, it is advantageous to utilize vertical wells to achieve simultaneous fracturing of these layers. This approach allows for the efficient and effective fracturing of multiple rock layers within a single well. The location and number of vertical wells and other parameters are the key to determining the fracturing effect. [PERSON] et al. obtained the propagation law of ground fracturing cracks and gave an example of a field fracturing application [40]. [PERSON] provided a variation law of fracturing position  
Figure 18: Schematic diagram of ground fracturing to prevent rock burst. under different mining positions, different strata, and different horizontal and vertical stress conditions, and revealed the selection criteria of the ground fracturing position under different mining conditions; this research provides a theoretical foundation for determining the optimal position for fracturing [41]. [PERSON] et al. conducted field tests and monitored microseismic events, which revealed that the highest frequency of microseismic events in the fracturing area decreased by 52.2%.