| The in-situ gasification of coal as a partial source for energy from conventionally unminable coal reserves has received increased international attention. Several technical, environmental, safety, and economic considerations have been indicated as potential advantages. The controlled extraction of this resource in addition to its sustained reliability requires laboratory experiments, mathematical modeling, and field tests. The prediction of temperature, stress, gasification chamber configuration, and subsidence profiles is a pre-requisite in evaluating process mechanisms, roof collapse, combustion stability, and optimization of commercial projects.;The thermo-mechanical changing boundary formulation is used to simulate several field tests. The computed gasification chamber configuration and the experimental field results are compared and favorable agreement is obtained. The thermo-mechanical formulation is demonstrated to be a practical technique in predicting the transient gasification chamber configuration and the ground movement. Recommendations for improving the thermo-mechanical formulation and computational techniques are given.;The thermo-mechanical responses of a continuum with changing boundaries are obtained by using the finite element method. Applications to underground coal conversion are illustrated. The energy generated by the coal combustion at the burn front is quantitatively introduced in the heat conduction equation. The gasification chamber configuration is defined by an assumed reference front isotherm. Thermo-elastic and thermo-plastic constitutive relations along with failure criteria are used in predicting the failure fronts. The incorporation of the burn front propagation and the collapse of failed overburden defines the overall gasification chamber configuration. Temperature dependent material properties are used to account for property changes in the vicinity of the gasification chamber boundary. |
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