Failure structure characteristics of strata with <a name="OLE_LINK10">upper thin and lower</a> thick strata in ultra-close coal seams with simultaneous mining and relationship between shield and surrounding rock

Failure structure characteristics of strata with upper thin and lower thick strata in ultra-close coal seams with simultaneous mining and relationship between shield and surrounding rock Journal of Mining and Safety Engineering . 2017, (5): 832 -837 .