Research On Evolution Law Of Gas Effusion And Spontaneous Combustion In Dynamic Goaf Based On Deformation Geometry

Goaf air leaking,poisonous and harmful gase mission,spontaneous combustion is the main risk factors of coal mine safety and efficient production.Coalface is a dynamic system,Boundary of coalface and goaf move with face advance,goaf from scratch length increased.At the same time of the geometric boundary and region range,Physical materials in goaf also increased gradually.With the continuous mining,the depth of goaf is increased.The related issues have evolved into the dynamic and unstable problem with the move of geometric and material coordinate system.In this paper,a Multiphysics COMSOL dynamic numerical simulation model is established based on the theory of deformation geometry.The boundary condition and initial value are defined by 014N1-1 fully mechanized caving face of Rui an coal mine.The reliability of the dynamic model was verified by the analysis of the field monitoring data.To further develop the dynamic evolutive law for the coefficient of bulk increase of caving coal in goaf,thinckness of lose coal,porosity,permeability,pressure distribution,air Leakage,gob gas,CO emission and accumulation,Spontaneous Combustion "Three Zone",the optimal position of gas drainage in goaf and Nitrogen injection.The mainly research work and results are as follows:A Case study of 014N1-1 fully mechanized caving face of Rui an,based on the deformation geometry method,a Multiphysics COMSOL dynamic numerical simulation model is established which working face mining line is fixed,the coal-face and roof caving line is moving with with the working face,Goaf up and down boundary is extended,as well as the goaf area and scope.It is proved that the dynamic numerical model is reasonable and reliable from the comparison of numerical simulation and field measurement results.In the dynamic process of the working face,the moving of the goaf and the dynamic growth of the area,Material parameters decay with mining time any point in goaf such as the coefficient of bulk increase,thinckness of lose coal,porosity,permeability.And the dacay rate decreases with the advancing speed of working face.Therefore,by improving the speed of the coal mining area to reduce the emission of toxic and harmful gases,and control the goaf spontaneous combustion.When the goaf area reaches a certain length,,the wind pressure gradient change into zero in the deep part of the area.Wind pressure gradient reversal which present the lower wind pressure is smaller than the upper wind pressure from the range of the region to the beginning of the mining area.During process of working face advancing,Goaf gas,CO emission dynamic change.The amount of the initial mining is low,With the exploitation of the duration,the amount of gas emission increase to maximum then decay gradually and tend to be stable.In the early production period,the larger the advancing speed of working face,the greater the gas and CO emission in the goaf,which conversely at a period of time.The greater the amount of air flow,the greater the amount of gas emission throughout the mining period.At the beginning of mining,the accumulation of gas and CO is at the maximum near the initial production line.With the process of the working face,the maximum concentration area is far from the initial production line.Gas and CO concentration is increased from low to maximum and then decreased from the top line to the starting line.Spontaneous combustion "three zone" of residual coal is varying width with continuous mining.The width of the oxidation zone has an approximate "S" shape growth trend with the mining time.At the mining earlier stage,the greater the air flow,the smaller the oxidation band width.which is adverse after the stability of oxidation band width.The influence of advancing velocity on the oxidation zone width is complicated.However,the ratio of the width of the oxidation zone and the advancing velocity or the proportion of the length of goaf is smaller with the high advancing velocity.With the continuation mining,the best position of the gas drainage and nitrogen injection in goaf are gradually far away from the roofcaving line.And the higher advancing speed,the greater deviation from the roofcaving line.A numerical simulation model of dynamic non-interval nitrogen injection in goaf is established.Which is proved that the method proposed in this paper can not only simulate the dynamic evolution law of goaf,but also be used for the dynamic optimization for the prevention and control technical parameters.