Stability evaluation method of gasification coal pillar under thermal coupling condition for prevention of...

The instability of gasification coal pillars can easily induce the further development of water-conducting fractures, which leads to the connection of gasification combustion space and aquifer, and then causes groundwater pollution. Therefore, it is crucial to assess the stability of gasification coal pillar to forestall the potential risk of environmental contamination resulting from underground coal gasification. In this paper, based on the shape of the combustion space area of underground coal gasification, considering the influence of the mechanical properties of the coal pillar and the temperature field under the condition of thermal coupling, the calculation method of the yield zone width of gasification coal pillar is proposed. Considering the destabilizing factors affecting the coal pillar and the relationship between actual and ultimate bearing capacities after stripping and yielding, a stability evaluation method for the 'hyperbolic' coal pillar is proposed. Additionally, the effects of various factors on the stripping, yielding, and safety factor of the coal pillar are analyzed. The new method was applied to the Ulanqab underground coal gasification test site, which proved its effectiveness. The research results are of great practical significance for designing underground coal gasification production and preventing environmental pollution.