## 5 Field Application of Directional Hydraulic Fracturing Unloading Technology
### Analysis of Fracturing and Pressure Relief Effects  
1. Fracturing effect analysis  
When most of the drill holes in the 30,116 return wind trench were pressed to the position of 11-17 m from the mouth of the borehole (most of the drill holes in the auxiliary transportation trench were pressed to the position of 20-29 m from the mouth of the borehole), the anchor ropes started to produce water. The closer the drill holes were to the borehole mouth, the greater the fracturing out of water, as shown in Figure 18a,b. This reflects that the surrounding rock above 17 m (29 m) of the borehole is relatively hard and complete and the fractures did not develop; under the action of high-pressure water, the fractures were also extended and diffused and new fractures were generated. The fractures in the surrounding rock below 17 m (29 m) were more developed, the penetration under  
Figure 16: Drill hole arrangement plan for 30,116 working face hydraulic fracturing top plate management. (**a**) 30,116 working face hydraulic fracturing top plate management return air duct drilling layout plan. (**b**) Return air duct drilling section plan. (**c**) 30,116 working face hydraulic fracturing top plate management auxiliary transportation channel drilling arrangement plan. (**d**) Auxiliary transportation channel drilling section plan.  
Figure 17: Layout of initial top release drill holes for hydraulic fracturing at 30,119 workforce cutting eye.  
the action of high-pressure water was better, and a fracture network was formed, as shown in Figure 19. Most of the fracturing values are distributed between 10 and 25 MPa, without an obvious pressure drop, and the phenomenon of neighboring holes drenching during the fracturing indicates that the cracks were extended to the neighboring holes, and the design of the fracturing scheme is reasonable.  
The primary difference between the 30,119 and 30,116 working faces is that in the 30,119 working face, most of the drill holes were pressurized to a depth of 10-19 m from the hole opening, at which point the anchor cables began to release water (as shown in Figure 18c,d). The majority of the fracturing pressures ranged between 10 and 22 MPa.  
Figure 19: Morphology of hydraulic fractures.  
Figure 18: Directed hydraulic fracturing effectiveness. (**a**) 30,116 return air fracturing water flow along the trough; (**b**) 30,116 transport fracturing water flow out of the trough; (**c**) 30,119 return air fracturing water flow along the trough; (**d**) 30,119 transport fracturing water flow out of the trough.  
The remaining principles governing the process are consistent with those applied in the 30,116 working face.  
2. Analysis after pressure relief  
To further assess the impact of roof management in the 3\({}^{-1}\) coal seam, pressure monitoring was performed on the brace resistance of the 30,116 working face at the Yanghuopan Mine following roof depressurization. Two monitoring channels were selected in each section of the upper, middle, and lower parts of the working face to analyze the mine pressure data (as shown in Figure 20). For data comparability, six channels--4-4, 6-6, 10-10, 12-12, 17-17, and 19-19--were used for data acquisition.  
Figure 20: _Cont._  
Analysis of the measured stent resistance data from the 30,116 working face, as shown in Figure 20, revealed distinct cyclic variations in stent resistance. The working face exhibited a cycle pressure step of 10-12 m, a cycle pressure range of 37-41 MPa, and a cycle duration of 3-4 days. This indicates that the directional hydraulic fracturing technology effectively reduced concentrated stress in the roof plate of the working face gradually, alleviated dynamic pressure in the quarry, and allowed the stent to function normally.  
Figure 20: Resistance curve of each stent after working face roof treatment.