Aimed at the severe strata behavior hazards caused by the occurrence of lateral thick and hard roofs in shallow-buried large-section roadways, a directional fracturing and roof cutting technology for lateral thick and hard roof zones in shallow-buried large-section coal mine roadways is proposed.
Key technologies of directional fracturing for such roof regions are investigated using a comprehensive approach including theoretical analysis, numerical simulation, and field testing.
An arrayed perforation directional fracturing technology for lateral thick and hard roofs in shallow-buried large-section roadways is proposed, with the following parameters: perforation diameter of 8 cm, perforation length of 50 cm, injection rate of 1.2 m³/min, and perforation spacing of 20 cm.
The results indicate that arrayed perforation-guided fracturing can promote timely caving of the thick and hard roof, effectively reduce strata behavior intensity, and mitigate roadway deformation.
This study can provide a reference for the prevention and control of severe strata behavior hazards associated with lateral thick and hard roofs in shallow-buried large-section roadways.
Aimed at the severe strata behavior hazards caused by the occurrence of lateral thick and hard roofs in shallow-buried large-section roadways, a directional fracturing and roof cutting technology for lateral thick and hard roof zones in shallow-buried large-section coal mine roadways is proposed. Key technologies of directional fracturing for such roof regions are investigated using a comprehensive approach including theoretical analysis, numerical simulation, and field testing. The results show that: compared with the minimum principal stress direction, the perforation direction acts as a relatively weak plane and can guide fracture initiation and propagation. Fluid pressure inside arrayed perforations weakens the dominance of the in-situ stress field, promotes fracture connectivity between adjacent perforations, and forms vertical sheet-like fractures around the borehole. Increasing the injection rate and perforation diameter enhances the guidance capacity of arrayed perforations and promotes vertical fracture propagation. As the injection rate increases from 0.12 m³/min to 1.2 m³/min, the fracture height increases by 310.83%; as the perforation diameter increases from 2 cm to 8 cm, the fracture height increases by 31.44%. However, increasing the perforation spacing weakens the influence of fluid pressure inside adjacent perforations, resulting in fracture-free zones between perforations and inhibiting the formation of connected fractures. An arrayed perforation directional fracturing technology for lateral thick and hard roofs in shallow-buried large-section roadways is proposed, with the following parameters: perforation diameter of 8 cm, perforation length of 50 cm, injection rate of 1.2 m³/min, and perforation spacing of 20 cm. Industrial application tests were carried out in the 122105 working face of Caojiatan Coal Mine. Monitoring and evaluation of the perforation-guided fracturing effect were conducted using microseismic monitoring, roadway section scanning, and bolt/cable stress measurement. The results indicate that arrayed perforation-guided fracturing can promote timely caving of the thick and hard roof, effectively reduce strata behavior intensity, and mitigate roadway deformation. This study can provide a reference for the prevention and control of severe strata behavior hazards associated with lateral thick and hard roofs in shallow-buried large-section roadways.
