Non-linear seepage model and it’s solusion methods of gas in coal body

Considering the changes of pore structure caused by the external force led to significant changes to the permeability of coal.Using the three shaft seepage test, gets the flow of the raw coal specimen through controlled the axial compression and confining pressure constant, solved the nonlinear least squares problem by using the quasi-newton method which gets the initial value by the improved genetic algorithm, then analysis and solves the non-linear seepage laws of the coal. The results show that the the new optimization algorithm can effectively solve the nonlinear least squares problem due to it solves the serious path dependence of the quasi-newton method and needn’t derivation during calculation process, it provides a feasible method to solve the non-linear seepage laws of the coal. Study on nonlinear seepage law of coal body by the method，we found that the permeability coefficient of coal increases with the increase of pore pressure and decreases with the increase of the volume stress, it’s the product of a quadratic function of the pore pressure and the negative exponential function of the volume stress.