Evaluation Method of Surface Subsidence Degree for Underground Coal Gasification without Shaft

Underground coal gasification (UCG) is a green mining technology with less interference to the environment of mining area. However, underground coal gasification also can cause surface subsidence, which will affect the mining area environment. Therefore, it is necessary to study the evaluation method of surface subsidence degree of underground coal gasification to provide scientific basis for environment influence assessment of underground coal gasification. However, few current researches are conducted on the evaluation of surface subsidence degree of underground coal gasification (UCG). To solve this problem, this paper firstly proposes the process for assessing surface subsidence degree of UCG, and then offers a new method of surface subsidence prediction of UCG based on continuum-stochastic medium theory by combining the characteristics of strata movement of UCG without shaft. Meanwhile, the new approach was applied to evaluate the subsidence degree of UCG experiment site of Ulanqab mine. It was found that the subsidence area of UCG test site was in Class I damage, and have slight impact on the environment of the mining area. The safety of ground buildings can also be guaranteed. The research results own important theoretical significance for the environment impact assessment caused by underground coal gasification and UCG industrialization.