A Numeric Simulation of Gas Migration in a Fully Mechanized Coal Caving Stope Based on Lattice Boltzmann Method

A numeric simulation of gas migration in a fully mechanized coal caving stope based on Lattice Boltzmann Method is put forward. A mining stope includes an inlet air tunnel, a return air tunnel, a working face and a goaf. There are two different states of air movement in a stope: turbulent flow in the inlet air tunnel, the return air tunnel, the working face (the three parts are simplified as working face) and seepage flow in the goaf, which fills with heterogeneous porous media, so gas movement in a mining stope is very complicated. To explore gas migration laws, two velocity-concentration double distribution models are constructed to simulate the flow field in the working face and the goaf respectively. They are computed in parallel. The flow field data in the working face and the goaf are exchanged through the block coupling algorithms, and the simulation of gas migration in the whole stope are realized. The simulation can get mass data about gas migration velocity, concentration and pressure and direct information about gas migration in a mining stope, which can provide basis for control gas migration.

I. Introduction

The fully mechanized coal caving method is a promising mining method in mining a thick coal seam in China. However gas concentration is always over limit when it is adopted. Coal mine fatal accidents in recent years are mostly caused by gas congregation. As a result, researches on law of gas migration in a mining stope will be meaningful. Up to now, There are some researches on this problem: Reference [1] created a complex partial nonlinear differential coupled equations based on theory of conservation law under turbulent flow for gas migration in working face and solved by SIMPLE method. Reference [2] described gas migration in tunnels and working face and the cause of gas congregation and analyzed the control method for gas congregation. This paper only does some qualitative researches without quantitative researches. Reference [3]–[7] adopted cell theory to analyze the sources of gas and obtain the laws of gas emission. The Lattice Boltzmann Method (LBM) has been developed into an alternative and promising numerical technique of Computational Fluid Dynamics (CFD) in recent years [8]. The obvious advantages of the method are parallel in nature because of locality of particle interaction and transition of particle information, and are flexible in geometry because of easy implementation of complicated boundary conditions and properties of a fluid system. Therefore, A LBM simulation is put forward to reveal and control gas migration in underground coal mine.