260 Fig.2 Schematic illustration of coordinated “support–destress” strata control for an ultra-large mining-height face. Curve 1 represent the mining pressure before destressing and curve 2 show it after destressing. The letter D and S represent destressing and support, respectively. 3.2 Ultra-Large-Height Hydraulic shields Hydraulic shields are the core equipment governing the feasibility of 10-m longwall mining. To meet the extreme demands imposed by the ultra-large mining height and strong ground pressure, 10-m ultra-large-height hydraulic shields were specifically developed (see Fig.3). These shields have the following characteristics. 1. Rated working resistance approaching 29,000 kN, providing sufficient support intensity for thick hard roof conditions. 2. A double-layer telescopic canopy combined with multi-level coal-wall protection, enabling simultaneous roof control and active protection of the ultra-high coal wall. 3. Enhanced stability, impact resistance, and structural reliability to withstand strong dynamic loading. These characteristics ensure effective roof control while significantly reducing the risk of coal-wall instability, which is a critical prerequisite for safe 10-m extraction. S
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