Abstract
An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical–mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid (coal) are modeled with the discrete element method, and the flow of fluid (gas and water) such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid–fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.
Highlights
An outburst of coal and gas is the rapid release of a large quantity of gas in conjunction with the ejection of coal and possibly associated rock, into the working face in underground coal mines
The deformation, failure and fracture of solid are modeled with the discrete element method, and the flow of fluid such as free flow and Darcy flow are modeled with the lattice Boltzmann method
This paper describes the basic principles and data interaction in the coupled discrete element method (DEM) and lattice Boltzmann method (LBM) model
Summary
An outburst of coal and gas is the rapid release of a large quantity of gas in conjunction with the ejection of coal and possibly associated rock, into the working face in underground coal mines. Along this strand of research, some attempts have been made to numerically model the process of an outburst, including mainly a phase transformation model (Litwiniszyn 1985), a gas desorption and flow model (Paterson 1986), a boundary element model (Barron and Kullmann 1990), an airway gas flow model (Otuonye and Sheng, 1994), a fracture mechanics model (Odintsev 1997), a finite element model (Xu et al 2006), a plasticity model, and a coupled solid–fluid model (Xue et al 2011) Despite these great efforts there is no single numerical model that can accurately simulate the entire process of an outburst because an outburst includes several interacting processes, including coal deformation and failure, coal fracture and fragmentation, gas desorption, mass transfer between adsorbed gas and free gas, flow of gas and water within coal cleats, gas dynamics and transport of failed and fragmented coal (Xue et al 2014). A simple example to simulate the process of an outburst is presented to demonstrate the potential capability of the coupled model
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