The Study On Porous Media Resistance Coffcient Of Goaf

Due to the complexity and variability of the coal goaf inside, measuring the goaf parameters by embedding sensors directly is very difficult, and its success rate and accuracy are very low. At present the study of goaf is mainly through tracer technology, analog simulation and numerical simulation. With the development of modern flow field theory and computer technology, numerical simulation technology is more and more applied to the study of goaf. The basic idea of using the FLUENT software to simulate the goaf is to consider the goaf at the back of the working face as a porous media region composed of coal and roof caving coal rock mass that has different porosity, the movement of mixed gases in the region accord with the law of mass conservation, momentum conservation, energy conservation and the component mass conservation, these control equations and some other additional scalar equations (e.g., turbulent transport equation) constitute a closed equation set, and then using finite volume method in the calculation domain discretize control equation set to obtain the whole flow field parameters.When using the FLUENT to simulate the porous media in goaf, the core problem is to determine the porous media resistance coefficient that can react the actual physical model. Based on FLUENT porous media model combined with Darcy Law, the paper summarizes and analyzes the basic rules of goaf caving overburden subsidence from the X,Y,Z three directions, establish a mathematical model that can reflect the general rule of goaf resistance coefficient3D continuous distribution, and uses the numerical simulation technology to discuss and analyze the parameters in the mathematical model, and studies the parameters’effect on the state parameters distribution in working face and goaf free field flow, through all of them the paper hopes to get more accurate description of broken rock mass accumulation state in goaf. According to the ventilation resistance law, the air volume, air pressure, wind resistance, we can determine another based on any two parameters, and make the pressure value as the boundary conditions of numerical simulation, the air volume that has been contrast iteration can be used as the setting basis of judging the porous media resistance coefficient in goaf.Take the15104fully mechanized working face in Yangquan Sijia Zhuang coal mine as an example, the paper analyzes the working face and goaf coupling flow field state and gas migration rule in goaf using the goaf resistance coefficient model based on field measured data, and in view of different drainage forms confirmations the effectiveness of gas comprehensive control measures.