1508 Fig.1 Schematic profile of multi-layer thick and hard roof strata above the 10-m working face. 2.3 Engineering Challenges Specific to 10-m Mining Height The combination of extra-thick coal seam and multi-layer thick hard roof results in a series of engineering challenges that intensify significantly with increasing mining height. When the mining height reaches 10 m, these challenges become fundamentally different from those encountered in conventional large-height longwall mining. First, the ultra-large excavation space significantly increases the scale effect of overburden movement, leading to strong ground pressure, long weighting intervals, and severe dynamic loading on the support system. Second, the ultra-high coal wall, exposed over a height of nearly 10 m, exhibits poor selfstability and a high tendency for spalling and sloughing, posing a direct threat to safe and continuous production. Third, the presence of thick hard roofs leads to large suspended roof blocks and violent roof failure once instability occurs, placing extreme demands on hydraulic shield capacity and reliability.In addition, the sharp increase in coal output per unit advance imposes unprecedented requirements on mining equipment, including hydraulic shields, shearers, and scraper conveyors, all of which must operate reliably under high loads, high power, and strong dynamic disturbances. These combined challenges explain why longwall mining heights worldwide had long remained below 9 m and why a 10-m mining height was widely considered unattainable prior to this project. 3. KEY TECHNOLOGIES ENABLING 10-M LONGWALL MINING Achieving fully mechanized longwall mining with a shield height of 10 m required a system-level technological breakthrough, rather than isolated improvements to individual components. The key enabling technologies include coordinated surrounding-rock control, ultra-large-height mining equipment, and reliable system integration under extreme operating conditions. 3.1 Coordinated Surrounding-Rock Control for Ultra-Large Mining Height With a 10-m mining height, conventional roof control concepts are no longer sufficient due to the ultra-large excavation space and the presence of multi-layer thick and hard roofs. A coordinated support– destressing control strategy was therefore developed to ensure overall stability of the longwall system. In the near field, high-capacity hydraulic shields provide strong active support to the immediate roof and effective protection to the ultra-high coal wall, suppressing roof separation, excessive subsidence, and coal-wall spalling. In the far field, large-scale underground hydraulic fracturing is applied to weaken and destress thick hard roof strata, reducing suspended roof span, lowering stress concentration, and mitigating strong periodic weighting. An overall schematic of the support–destressing coordination concept is shown in Fig.2. This coordinated control approach effectively combines near-field strong support and far-field roof weakening, 1100 1080 1060 1040 1020 980 960 Supplementary Borehole No. 58 Supplementary Borehole No. 65 Borehole at 5900 m Borehole at 5600 m Borehole at 5100 m Borehole at 4500 m Borehole at 4100 m Strata Level (m)
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