Research On Effect Mechanisms Of Mining Speed On Mining Induced Influences Around Deep Working Face With Thick-hard Roof

In view of the lack of quantitative representation of the influence of the accumulation/release of energy in deep thick-hard roof on the risk of coal body impact failure in eastern mining area and the lack of theoretical basis for determining the mining speed of deep thick-hard roof working face,based on theoretical analysis,numerical simulation analysis,laboratory test,field measurement and engineering practice,the effect mechanisms of mining speed on mining induced influences around deep thick-hard roof working face are systematically studied.The main achievements are as follows:(1)The concept of energy key layer on deep thick-hard roof working face was put forward,the determination idea and discrimination basis of energy key layer were expounded,and the correlation and difference between energy key layer and structural key layer were clarified.The quantitative relationship between the load rate of the energy key layer and the mining speed of the working face was determined.The calculation model of the ultimate span and flexural elastic energy of the energy key layer during the initial breaking and periodic breaking considering the mining speed was established.The influence of the thickness and strength of the energy key layer on the sensitivity of the flexural elastic energy to the mining speed was analyzed.(2)A numerical analysis model of mining influences on deep thick-hard roof working face was established,and the influence law of mining speed on distribution and evolution of mining-induced stress and elastic strain energy of coal seam,as well as the deformation failure of energy key layer and distribution and evolution of elastic strain energy were studied.Taking the mining-induced stress concentration coefficient of coal seam,the abutment pressure recovery coefficient of goaf,the elastic strain energy accumulation coefficient of coal seam and the energy release coefficient of energy key layer as the main evaluation indexes,the mining speed effect of the mining-induced stress and energy evolution of coal and rock mass under different mining height of coal seam and different strength of coal body was analyzed.(3)The quantitative relationship between the mining speed at the working face scale and the axial displacement loading rate and confining pressure unloading rate of the coal rock mass at the laboratory scale was determined.The uniaxial compression of the coal rock mass under different displacement loading rates and the triaxial loading and unloading tests of the coal rock mass under different confining pressure unloading rates under the mining stress path were carried out.The characteristics of strength,deformation,failure and energy evolution of coal rock mass under the effect of mining speed were analyzed,and the formation mechanism of mining stress concentration and elastic energy accumulation under the effect of mining speed was revealed from a mesoscopic perspective.(4)Based on the principle of minimum energy of coal rock mass dynamic failure and the principle of static and dynamic loading superposition,a quantitative evaluation model of impact failure intensity of coal mass was established with the evaluation index of elastic residual energy of coal mass at different mining speeds,and the evolution characteristics of elastic residual energy of coal mass under different mining conditions were analyzed.The control idea of mining strength of working face based on the effect of mining speed was put forward,and the engineering practice and effect test were carried out to realize the optimization of mining strength and safe mining of deep working face with thick-hard roof.This thesis has 135 figures,14 tables and 187 references.