Defend is difficult since its stability is bad, often bring face roof fall, the roof management is very difficult.
由于其稳定性差、维护困难，经常造成工作面顶板冒落，给顶板管理带来了很大困难。
Based on the local, migratory and subsection characteristics of main roof fall of longwall face, the main roof was divided into some plate group, and plate group mechanical model was established.
针对长壁工作面顶板垮落具有局部、分段、迁移的时空特征，将长壁工作面采场顶板划分成若干个相互铰接的薄板，建立了薄板组力学模型。
Defend is difficult since its stability is bad. It often brings face to roof fall. The roof management is very difficult.
由于其稳定性差、维护困难，经常造成工作面顶板冒落，给顶板管理带来了很大困难。
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