Numerical Investigation of the Influence of Roof-Cutting Parameters on the Stability of Top Coal Gob-Side Entry Retaining by Roof Pre-Fracturing in Ultra-Thick Coal Seam

• Published in: Energies (Basel) Vol. 16; no. 12; p. 4788
• Main Authors: Yang, Yongkang, Gao, Peipeng, Zhang, Chao, Wang, Chenlong
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.06.2023
• Subjects: Analysis; Boreholes; Coal; Coal industry; Coal mines; Coal mining; Continuous production; Cutting parameters; Deformation; Engineering; Failure mechanisms; Fracturing; Geology; Investigations; Load transfer; Mineral industry; Mining; Mining industry; Occupational health and safety; Overburden; roof pre-fracturing; roof-cutting parameters; Stability; Stress concentration; Sustainable development; Thickness; top coal gob-side entry; ultra-thick coal seam
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en16124788

Gob-side entry retaining by roof cutting, a pillarless mining technique, plays a critical role in maintaining continuous production, rapid connection, and enhancing the coal recovery rate in fully mechanized top coal caving working faces. This technique stands as a sustainable development method in coal mining. The present research, set against the backdrop of the Yitang Coal Mine 100602 top coal gob-side entry retaining by roof cutting, investigates the influence of roof-cutting borehole depth, borehole dip angle, mining height, and coal seam thickness on stability in an ultra-thick coal seam under 12 distinct mining conditions. A typical model of overburden structure post-roof pre-splitting was established to study the failure mechanism of the top coal roof. The results reveal that the dip angle and depth of the roof pre-fracturing borehole significantly impact the movement characteristics of the overlying strata. Optimal conditions are found when the dip angle and depth of the roof pre-fracturing borehole, the mining height, and the top coal thickness are 10°, 16 m, 4 m, and 4 m, respectively. Under these circumstances, the load transfer from the goaf to the gob-side entry can be effectively intercepted, mitigating the influence of roof fracture activities on the top coal gob-side entry. Field measurements confirm that suitable anchor-net support can stabilize the roof’s rock structure. This research underpins the significance of roof pre-fracturing for the promotion and application of top coal gob-side entry retaining by roof cutting in ultra-thick coal seams.