Research Of Goaf Seepage Field And Its Permeability Coefficient At Fully Mechanized Caving Working Face

The composition of goaf space in coal mine was complicated, and the air-leakage in goaf was the only way to supply the aerobic for coal spontaneous combustion in goaf. The seepage space parameters’ change in goaf influenced the seepage flow field directly, and then, the distribution of three zones of coal spontaneous combustion would be affected. Therefore, the researches for seepage space and its characteristics was becomes to particularly important. The goaf formed by full-mechanized caving mining face has a large space and more residual coal, its seepage space and the seepage characteristics would changed with different caving ratios, there will be a law should be finded. The analysis of these problems was the basis of the research for seepage laws in goaf formed by fully-mechanized caving, as well as the theory support of disaster prevention and control technology.Combined with the actual situation of coal mine, in this paper, theoretical analysis, experimential and numerical simulation research were used to analyze the content as follows:the form characteristics of seepage space and its influencing factors; regard the caved rock or coal which closed working face as a free porous media, made some experiments about the relation among seepage velocity, pressure gradient and particle size, analyzed the rate of flow for seepage state transition; build the three-dimensional model for seepage in goaf, made some experiments about the resistance distribution of working face how to affected the differential pressure, and the seepage pressure in goaf; proposed a mothod to ascertain the size of goaf, based on stress distribution in goaf formed by fully mechanized mining and caving working face, and used the UDEC to build models to simulated goaf size, with mining and caving ratio was 1:1, 1:2 and 1:3, analyzed the laws of seepage space on trend and inclined; used the Fluent to analyze the laws of seepage in goaf with different mining and caving ratio, analyzed the resistance distribution how to affect the differential pressure and seepage in goaf. Finally, through the analysis of field measured data, proved the correctness of experiment and numerical simulation.Through these researches, we obtained the following conclusions:in the same scope of seepage velocity, the seepage pressure gradient was becomes small, with the increase of particle diameter which constituted the porous medium, the transformational seepage velocity was decrease, which made seepage state transformed to turbulent flow from laminar flow. Coefficient of permeability and the transition seepage velocity in heterogeneous porous media were mainly depend on the proportion of small size particles. Under the same geological conditions, the seepage space was decrease on horizontal plane, with the mining and caving ratio added in fully-mechanized caving working face, in the special thick coal seam. the distribution of seepage velocity field in the goaf with weaker symmetry, in the seam range of seepage velocity, the scope of return airway side was bigger than the scope of intake airway side, with the mining and caving ratio increase, on the trend direction, the turbulent region and transition seepage region were decrease, on the tendency direction, the turbulent region decrease and transition seepage region increase. when the resistance of working face main distributed on intake airway, return airway and middle of the working face, the pressure difference was reduce by turns, and the seepage in goaf was appear significant asymmetric distribution, when the resistance distributed at intake airway and return airway.