| The mining depth of shallow mining areas in Shaanxi and Inner Mongolia is generally 53～280m,while the mining depth of deep mining areas has generally exceeded 580m,and the mining depth has increased at a rate of tens of meters per year in recent years.According to the field investigation,the deep mining areas in Shaanxi and Inner Mongolia generally have high-intensity mining,strong rock burst tendency of coal seam,large-scale water-rich areas and thick-hard key strata.During the mining process,over ten dynamic disasters,such as rock burst and mine earthquake,have occurred in some mines,which seriously restricts the safe and efficient production of the deep mining areas.This paper focuses on the frequent occurrence of dynamic disasters in deep mining areas.Typical dynamic disasters that recently occurred at deep mines were taken as the research background,this paper investigates the occurrence mechanism and prevention technologies of typical dynamic disasters through case investigation,theoretical analysis,similar material simulation test,numerical simulation and field measurement and so on.The obtained results are as follows:(1)According to the investigation and analysis of mining conditions and characteristics of dynamic disasters in the deep mining areas of Shaanxi and Inner Mongolia,the types of force sources of dynamic disasters were determined,and the dynamic disasters were classified in three types,mainly including rock burst induced by mining and water drainage stress superimposition,rock burst induced by stress superimposition at wide segment pillar,and mine earthquake induced by hard-strata breaking under the support of isolated coal pillars.(2)Through establishing the mechanical model for estimating the abutment pressure on the working face after water drainage and the abutment pressure distribution model under high-intensity mining,the effects of drainage and high-intensity mining on the stress distribution law of the working face were investigated,and then the mechanism of rock burst induced by mining and water drainage stress superimposition in deep well working face was revealed.The pressurized zone and pressure-relief zone are formed after drainage.When the working face was rapidly mined through the pressurized area,the superposition of the mining stress and the pressurized area stress exceeded the critical value of rock burst,which is the main reason to induce the rock burst.On the basis,the dynamic changes of the rock burst hazard areas before and after drainage were predicted,and a dynamic control method of mining speed in drainage area was proposed.(3)The stress distribution laws of coal pillars with different depths and widths under typical mining conditions in the mining area were studied,and the failure zone characteristics of wide segment pillars under specific conditions were analyzed.The impact mechanical model of wide segment pillars was established,then the mechanical discriminant condition of the coal pillar induced rock burst was given,and the mechanism of rock burst induced by stress superimposition on wide segment pillars was revealed.Based on this,the rock burst prevention measures and strategies caused by wide segment pillars in deep mining areas,and the design of narrow coal pillar width in the next stage were put forward.(4)A mechanical model of flexural deformation at main key strata,and a estimation model of isolated coal pillar compression under the condition of coal pillar support were established respectively.The criterion for determining the fracture induced by the flexural fracture of the key strata was provided.The mechanism of mine earthquake induced by the fracture of hard-strata was revealed Based on the mechanism,a design method for the reasonable width of isolated coal pillar was provided to coordinated control of rock burst and mine earthquake.The research findings have been applied into three rock burst mines in the Nalinhe and Huerjite mining areas of Shaanxi and Inner Mongolia,and the results are good. |
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