For the tip - to - face roof stability , chock - fram type powered support only be applied to hard top - coal , shield - type powered support and chock - shield - type powered support can be applied to three top - coals 通过分析,为保证端面顶板稳定,支撑式液压支架仅适用于顶煤为硬煤的条件下,掩护式和支撑掩护式支架在三种顶煤条件下均可以适用。