Stress Evolution And Rock Burst Gestation Law Caused By Thick Coal Seam Mining In Fold Region

Rock burst is a typical coal or rock dynamic disasters in coalmines,thereinto tremor evolution law caused by thick coal seam mining in fold region is still not clear.In this dissertation,geometry characteristics,fold morpgology and coal thickness variation of Northwest fold,the distribution and evolution of stress and energy and its impacts sensitivity during the formation and coal seam mining of folds,and focus features of high-energy tremors in fold region were systematically studied using a combination research method of theoretical analysis,numerical simulation and engineering practice.An investigation was firstly conducted on fold morpgology and coal thickness variation of Northwest fold based on the survey data in Hua-ting Coalmine,Yan-bei Coalmine,Hu-jiahe Coalmine and Cui-mu Coalmine,which was aimed at providing a basis for the following numerical study.Results showed that the folds in investigated coalmine were mainly gentle folds(fornix and basin),of which aspect ratio was between 0.78 and 2.03,the max-curvature and curvature-ratio of fold's transverse section were totally below 0.04 and 1.4,89% of the angles of limbs of fold were greater than 150°.Creep model was built based on statistical analysis of geometry characteristics of folds,the impact on the distribution of stress and energy concentration of influencing factors was analyzed,such as fold geometry characteristic,coal and rock thickness,property of coal and floor and roof,which revealed the difference of factors on the fold formation process and laid the foundation of the building of Rock Burst risk function.The stress transfer and energy dissipation law were analyzed.Energy-polling region in syncline mainly scatter in the floor of coal seam in front of extracting face,while for the conticline,mainly scatter in the coal seam around extracting face.The stress concentration region transfers from rock floor to lower layer of coal seam in syncline along with the decresing of bottom coal thickness which is the contrary in conticline area.In this paper,the research employed the method of seismic moment tensor inversion which provides parameters of focal mechanism(percentage share of its components: isotropic,uniaxial compression or tension,shear component;trend and dip of nodal planes,et al)based on the analysis of geological and mining conditions,The conducted test showed that the type of ruptures were all distinguished as tensile failure,which preliminarily revealed the tremor gestation law in fold region.Taking Yan-bei Coalmine and Hu-jiahe Coalmine whose working faces were with strong tremor risk for on-site practice,where high fidelity geological model based on terrestrial Stress test was build,meanwhile,distribution law of high-energy tremors and apparent stress in mine stope were analyzed.