Development of a thermo-mechanical model for rocks exposed to high temperatures during underground coal gasification

In the wake of increasing challenges of high prices of oil and gas and uncertainties about political stability in many oil and gas producing countries, coal becomes more and more important in the coming years for its vast reserves and wide distribution all over the world. The technology of Underground Coal Gasification (UCG), converting in-situ, unmined coal into combustible gases, has continued to attract worldwide interest because of its ability to exploit coal which is otherwise unminable by conventional mining techniques due to deep deposit depths, thin seam thickness or low quality, in an economical, safe and environmentally friendly manner. Ground subsidence seems to be an inevitable consequence of underground cavities formed by a commercial-scale UCG project. Unlike other mining methods (longwall mining, room-and-pillar mining, etc.), the rocks and coal in the vicinity of a UCG reactor are subjected to high temperatures which may be in excess of 1000 °C. Thus, the purpose of this thesis was to predict UCG-induced ground subsidence by application of a thermo-mechanical rock failure criterion which involves hightemperatureinfluences on rocks.