A coupled approach to simulate initiation of outbursts of coal and gas — Model development

Abstract

An outburst of coal and gas is a major hazard in underground coal mining. It occurs when certain conditions of coal stress, strength and gassiness are met. The outburst is recognized as a two-step process, i.e. initiation and development. Each step has its own characteristics and requires different approaches in numerical modeling. As a first step, the initiation process of the outburst is numerically simulated with a coupled simulator. The simulator models the deformation and failure of a coal seam, adsorption and desorption of gas and flow of gas and water in coal. The simulator is developed by linking and sequentially executing two numerical codes: FLAC3D and COMET3. FLAC3D is a widely used commercial code designed for engineering mechanics computation, while COMET3 is a well-established code to model gas and water production from desorption-controlled reservoirs. In this paper, these two codes are linked and sequentially executed through coupling modules including a user-designed C++ module and several modules developed with the build-in FISH language in FLAC3D. These coupling modules are used to transfer relevant data between the codes. A simple example to simulate the initiation of the outburst is also presented in this paper to demonstrate the capability of the coupled simulator. ► A coupled simulator has been developed by linking and sequentially executing two numerical codes of FLAC3D and COMET3 through coupling modules including a user-designed C++ module and several modules developed with the build-in FISH language in FLAC3D to simulate initiation of outbursts of coal and gas. ► A simple 2-dimensional model of roadway development in a coal seam was created with the coupled simulator to demonstrate the capability of the coupled simulator. The simulator modeled coal deformation, pore pressure, principal stress vectors and yielded zones as the roadway development advances.