Method To Predict The Surface Subsidence Based On The Key Strata Structure

The prediction of the strata and surface subsidence as well as deformation after the coal seam mining affects the safety and efficiency of coal mines.But most predicting methods adopts the idea of pure statistics,without considering the mechanical mechanism of the strata and surface subsidence.In view of this,this dissertation integrated the theoretical analysis,similar simulation,numerical simulation and in-situ measurements etc.and comprehensively studied the cracking and broken height of the overburden,the subsidence of the voussoir beam structure(VBS)and non-broken key strata(KS),the movement and deformation model of the surface based on the coupling effect of the KS and topsoil.The second chapter defined the cracking and broken height of the overburden.The cracking means that a layer has non-through fractures while the broken means oppositely.The first strength theory was used to establish the critical subsidence condition of the overburden cracking.The results shown that the whole overburden cracked after coal seam mining.Given this,the strata subsidence with different crack penetration was numerically simulated,which presented that the subsidence without and with different crack penetration was equal.Therefore,the continuum mechanics is applicable to research the subsidence of non-broken strata.The criterion and calculation process for the broken height of the overburden was established based on the stress development of the strata fracturing and the broken characteristics of rock strata in similar simulation.The second chapter also established the mechanical model of the subsidence of the VBS based on the structural mechanics,analyzed factors affecting the subsidence of VBS,provided calculation steps for the subsidence of the VBS,and validated the mechanical model based on the measured data of the Kongzhuang coal mine.The third chapter built the mechanical model of the subsidence of the strike and dip of non-broken KS based on the continuum mechanics,established the calculation method of parameters needed in the mechanical model,and studied the height of the KS,the modulus elasticity and the foundation coefficient of the gob,which affecting the subsidence curve of the KS.The fourth chapter studied the characteristics of the topsoil movement and deformation,established the prediction model of surface movement and deformation based on the subsidence the KS structure,and verified the model by similar and numerical simulation.The fifth chapter provided and complied with the Maple the procedure for the method to predict the surface subsidence based on the movement law of the KS,verified the method to predict the surface subsidence without topsoil based on the movement law of the VBS using the surface subsidence data of the 31305 panel in the Dongsheng coal mine and compared the results calculated by probability integral method,validated the method to predict the surface subsidence with topsoil based on the movement law of the VBS using the surface subsidence data and measurements of S18 borehole of the 31401 panel in the Bulianta coal mine,and verified the method to predict the surface subsidence with topsoil based on the movement law of the non-broken KS using the surface subsidence data of the 305 panel in the Tingnan coal mine.