Study on rock pressure law and control technology under multi-layer hard roof in fully-mechanized top coal caving face

Geological conditions of thick coal seam and multi-layer hard roof tend to result in the hydraulic support being crushed and rib spalling at the working fac e, as well as serious deformation of surrounding rock of the gob-side roadway together with dramatic strata behavior. The focus was laid on the fully-mechanized top co al caving mining face at Tongxin Mine, where the stress and deformation of surrounding rocks under the influence of multi-layer hard roof were monitored and analyzed. The results show that the mining stress generated by mining face has a large influence range. Under the impact of multi-layer overlying hard roof, the large overburden structure is formed, and the stress and deformation of the surrounding rock are"abruptly ascending"and" abruptly descending", alternately. The synergy of the large coal mining space and the multilayer hard roof are the main reason for the serious deformation in the fully-mechanized top coal caving face. The control technology of ener gy dissipation and bracing with constant resistance and large deformation of anchor in hard and long-stay tunnel with hard pre-fracturing blasting is proposed, which ca n effectively prevent and control the strong mining pressure. Keyword: extra-thick seam; multi-layer hard roof; strata behavior; overburden large structure;