Mechanical Mechanism Of Splitting Type Rock Burst In Working Face Under Thick And Hard Roof In Shendong Mining Area

There are abundant thick coal resources in Shendong mining area in China,with simple geological structure and superior mining conditions,which are suitable for the high-intensity mining with large mining height and rapid advancement.However,the whole cutting off and large area weighting of thick and hard roof tend to be leaded by the high-intensity mining in working face,thereby inducing the dynamic disaster of splitting type rock burst.The mechanical mechanism of splitting type rock burst in working face under thick and hard roof in Shendong mining area is researched systematically,by adopting the theoretical analysis,numerical calculation,and field monitoring in this thesis.The main research achievements are obtained as follows:(1)According to the basic characteristics of working face under thick and hard roof at different mining stages in Shendong mining area,the mechanical models of medium-thick plate under different boundary conditions(first mining face initial fracture,first mining face periodic fracture,lower section initial fracture,lower section periodic fracture)are established.The analytic solutions of deflection,bending moment and shear force of thick and hard roof under different boundary conditions are obtained by finite integral method.The corresponding numerical solutions are obtained by Matlab mathematical software programming.The influence rules of thickness to width ratio and width to length ratio on deflection,bending moment and shear of thick hard roof are studied.Based on the basic failure criterion of rock mass,the crack development and fracture morphology characteristics of thick and hard roof are determined.Based on the mechanical model of medium-thick plate,the deformation and fracture law of thick and hard roof are revealed,which lays a theoretical foundation for studying the rock burst mechanism induced by the dynamic instability of thick and hard roof.(2)By analyzing the mechanical mechanism of dynamic instability of coal wall crack body induced by the breakage of thick hard roof,a two-body mechanical model composed of thick and hard roof and coal wall crack body is established.The energy evolution law of rock burst on the working face of thick and hard roof is obtained.The basic equilibrium control equation of two-body mechanical model is established,and the fold catastrophe model of splitting type rock burst is deduced,revealing the mechanical mechanism of splitting type rock burst at working face under thick and hard roof.Specifically,the coal wall crack body reaching the strain-softening stage after the peak strength is realized by the dynamic load generated by broken thick and hard roof,which is a sufficient condition for the dynamic instability of the two-body system,namely,the external reason for splitting type rock burst.Besides,the coal wall crack body owns the post-peak strain softening characteristics,and the stiffness parameter of the two-body system is less than 1,which is the necessary condition of dynamic instability of the two-body system,namely,the internal reason for splitting type rock burst.(3)By analyzing the field measurement data at 42105 working face of Buertai coal mine in Shendong mining area,the basic characteristics of rock burst of thick coal seam with gangue layers are obtained.The UDEC discrete element numerical simulation software is employed to study the change law of splitting type rock burst under the conditions of different gangue locations,thicknesses and densities.By designing the orthogonal test scheme of numerical simulation of rock burst with different gangue inclusion parameters,selecting the width and depth of coal wall as the main evaluation indexes,the sensitivity of each gangue inclusion parameter to coal wall rock burst is studied by means of analysis of variance and significance test.The influence law of gangue inclusion parameters of thick coal seam on splitting type rock burst of coal wall in Shendong mining area is obtained.The research achievements can be treated as an important basis for the prevention and treatment of splitting type rock burst in working face under thick and hard roof in Shendong mining area.There are 62 figures,9 tables and 87 references in this thesis.