Research on the surface movement rules and prediction method of underground coal gasification

With the continuous development of the technology of underground coal gasification (UGC), it gradually moves into commercial development. However, there is limited measured data and related research on the overlying strata and surface movement rule caused by underground coal gasification, which has severely restricted the further application of underground coal gasification. In order to solve the problem of surface subsidence prediction of underground coal gasification, this numerical simulation software, FLAC^3D, is adopted to study the differences of overlying strata and the surface movement rule of UGC strip mining (UCG mining) and strip mining, and the differences of prediction parameters under different recovery ratios. The model is established according to the geological and mining conditions of the underground coal gasification experiment area in China. The research results show that overlying strata and surface movement rules of UCG mining and strip mining are similar. So, the surface subsidence prediction of UCG mining can refer the prediction method of strip mining. Meanwhile, the difference values of surface movement extrema under different recovery ratios are less than 5 mm and the difference values of surface subsidence boundary are not more than 10 m. Therefore, the surface subsidence prediction parameters of UCG mining can be chosen as the corresponding prediction parameters of strip mining. Finally, the surface subsidence prediction method of UCG mining is proposed based on the above research results and prediction software is compiled for engineering application. Research results have important theoretical and practical significance for promoting the application of underground coal gasification.