Research On Mechanism And Instability Control Of Coal-rock Mass Due To Mining Disturbance Near Fault Zone

The appearance of destabilization and unloading of complex coal-rock masses in fault area influenced by mining disturbed zone(MDZ)easily resulted in a large-scale caving of the coal-rock masses,indeed,dynamic hazards of surrounding rock often happened in the site,which would restrict safe mining severely.Therefore,to explore and offer a methodology on stability control and characteristics of movement-deformation of the strata in the fault area is directly necessary to guarantee the safe mining.The research sets safe mining of coal resource at Qingshuiying colliery,Ningdong coal district influenced by MDZ in the reverse fault area as engineering settings.Basic studies on stability control of coal-rock masses influenced by MDZ in fault area have been obtained by hybrid research ways including site engineering investigation,theoretical analysis,physical simulation experiment,numerical simulation testing and in-situ application.All research achievements are listed below.(1)According to relevant results from in-situ monitoring techniques,including sonic drilling,geological settings of the coal-rock masses in Ningdong coal district are extremely complex.In particular,variations in both lithology and thickness are obvious.The coal-rock masses are loose and weathering remarkably.Besides,the coal-rock masses is easy to degradation in water.All the geological settings here can be fundamental factors to induce dynamic hazards.With comprehensive parametrical analysis including scanning electron microscope,acoustic emission and other traditional experiment means,traits of microstructure distribution of the coal-rock mass in the fault area has been revealed.Simultaneously,the mechanism on spatial-temporal evolution deriving from fracturing inoculation fracture to destabilization induced hazard of the coal-rock masses have revealed in the analysis process.All the fundamental factors provide to safe mining,prediction and prevention of the hazard.(2)An evolution mechanism of coal-rock masses has been analyzed thoughtfully by analytical computation and comprehensive analysis under large height mining.The evolution mechanism can fall into four stages including deformation,caving,compaction and destabilization induced hazard considering MDZ in the fault area.On the strength of theory on structural mechanical equilibrium and Transformation energy of the coal-rock masses,maximum scale and location of triangle coal from coal wall caving has quantitatively confirmed in different periods like normal excavation and through fault.(3)Using physical simulation experiment and 3D-numerical computation,movement-failure characteristics of strata from both hanging wall and footwall have been offered influencing by MDZ in the fault area.Moreover,the evolution mechanism of stress and deformation of the coal-rock masses has been offered at the same time,relevant results indicate that roof structure is instability being induced by shear slip of the fault.Arc-shaped arch in overburden strata would be damaged due to concentration and release of accumulated energy.Besides,parameter values of acoustic emission are totally varied between internal roof and external roof in the fault area.There are a large-scale caving of the overburden strata in the fault area with the influence of MDZ from large height mining.Specifically,the stress,the distribution scope of slipping zone and plastic zone both hanging wall and footwall of the fault area have remarkable discrepancies.(4)Based on physical-mechanical properties of the coal-rock mass and dissimilarity of the stress and deformation in the MDZ,the process of chained evolution of hazard induced by coal-rock mass destabilization has finally analyzed.We provide a engineering hazard control method and its crucial idea is to eliminate internal-external causes for breaking the hazard-happening chain.We can combine bolting-grouting technique to control the strata structure.The technique can improve adaptive ability and mutual effect of the coal-rock mass.In addition,we adjust supporting parameters such as use of shed and crown hinge.In the end,the process of chained evolution of hazard can be controlled and achieve synergistically compaction and supporting of coal seam.(5)In virtue of the evolution mechanism of stress-deformation characteristics,the engineering hazard control method has been applied preliminarily.The strength of the coal-rock mass improved immediately and ability to defy deformation resistance increases.Finally,probability of fault activation declined sharply.Site data from in-situ monitoring also verify rationality and applicability of the methodology.The research offers physical-mechanical properties of the coal-rock mass in the fault area of Ningdong coal district.Analyze the specific mechanism of underground pressure in the large height mining and the methodology for prediction and prevention of the chained hazard has been obtained because of definite mechanism of the induced chained hazard.Ultimately,all research achievements offer a methodology and theory for safe mining of complex coal-rock mass influenced by excavation disturbed zone in fault area.At the same time,it would be a valid theoretical and engineering reference for other coal resource exploitation with a similar setting in Ningdong coal district and the whole country.