Support-pressure relief coordination control and asymmetric deformation and failure key control factors of gob-side entry in fully mechanized caving face

Aiming at the problems of reasonable coal pillar retention, multiple disturbances in mining, large cross section, and weak thick top coal in full-mechanized caving mining along the gob of thick coal seam, using the method of combining field investigation, theoretical research and engineering practice, the asymmetric deformation and failure characteristics of the surrounding rock in the fully mechanized gob-side roadway are analyzed, the essential reasons and main controlling factors are revealed, and the surrounding rock control requirements of gob side entry in large section fully mechanized top coal caving face and the support pressure relief cooperative control technology system are put forward.Investigation results show that the obvious asymmetric distribution of overburden structure and stress in vertical and horizontal direction of roadway section is the essential reason for surrounding rock asymmetric deformation and failure of gob-side entry in fully mechanized top coal caving workface.Multiple disturbance of excavation and mining, key block rotary motion, soft and thick top coal, existence of weak body in surrounding rock, large cross section size of roadway, unreasonable support are key control factors causing asymmetric distribution of overburden structure and stress.Control technology for surrounding rock of gob-side entry in fully mechanized top coal caving workface should meet the requirements of adapting to the asymmetric deformation characteristics of roof, having strong shear resistance, improving the bearing capacity of coal pillar, manually intervening the structural characteristics of overburden and improving the stress environment.During the whole service period, influenced by excavation and mining disturbance, roadway deformation mainly is appeared that large sidewall convergence, while roof subsidence and floor heave are small.The hydraulic fracturing pressure relief technology could significantly reduce or transfer surrounding rock high-level stress, reduce weighting strength of working face by changing the roof overburden structure.The coordination control technique of high pretension, intensive and differentiation support in near field coupled with hydraulic fracturing pressure relief in far field could adapt to the surrounding rock asymmetric deformation characteristics and control the deformation and failure in gob-side entry with small coal pillar and large cross-section in fully mechanized top coal caving workface.