Mechanical model and fracturing characteristics of multi-area supporting roof in fully mechanized mining working face

The excavation thickness and width of fully mechanized mining working face are large,and the roof failure conditions and influencing factors are complex. To research the fracturing characteristics of the roof in fully mechanized mining working face,the main roof was taken as the unite width plate supported by the four areas including the intact rock,hydraulic support,goaf and filling body formed by collapsed roof. Then the mechanical model of multi-area supporting roof in fully mechanized mining working face was set up,and the corresponding finite element program was de- veloped. The loads and periodic caving pace of main roof were deduced by the model combined with the dichotomy. The model in this paper was employed to investigate the distribution of the moment and shear force in fully mechanized caving working face of Cuimu coal mine. The conditions,influencing factors and laws of fracturing in front of coal wall, at the coal wall or in goaf were analyzed and researched. The results show that the maximum moment of multi-area sup- porting main roof happens in front of coal wall. If the tension failure of main roof happens in front of coal wall,the boundary condition of main roof is changed. Redistribution of the moment of main roof makes the maximum moment appear at coal wall,and the tension failure maybe happen. Otherwise,with the workface advancing,the maximum mo- ment of main roof increases. The position of the maximum moment offsets to goaf,and the main roof will fracture in goaf. The maximum moment position of main roof is influenced by the support stiffness,tension strength and thickness of main roof. With the increase of support stiffness,tension strength and thickness of main roof,the position of the max- imum moment offsets to goaf,which will easily lead to fracture in goaf. The maximum shear force position of main roof is influenced by the support stiffness,periodic caving pace and thickness of main roof. With the increase of support stiffness,periodic caving pace and thickness of main roof,the position offsets to goaf,which will easily lead to fracture in goaf.