Abstract: To obtain the surface sinking regularity in the case of super-subcritical extraction of shaft pillar by underground coal gasification (UCG) at former Ankou Coal Mine in Huating, Gansu Province, the first observation station in China for overlying strata movement and surface subsidence of strip-partial UCG working face is established. After the analysis of dynamic subsidence progress of surface measuring point and magnetic rings in surface shallow base point observation drilling, it is found that the subsidence curve shows the fluctuant and stepwise subsidence pattern which has five stages (sinking → rising → sinking → rising → sinking), and the surface movement and deformation of super-subcritical extraction of strip-partial UCG working face are obviously characterized by nonlinearity and discontinuity. The strata separation area is positioned by analyzing the dynamic subsidence progress of different magnetic rings. The geophysical prospecting finds that the projection plane of combustion space area seems like an oval, wide in the middle and narrow at both ends. The greatest subsidence angle, boundary angle of incline main section of subsidence basin and the maximum surface movement and deformation parameters (imax = 1.385 mm/m, εmax = 0.516 mm/m, Kmax = 0.275 mm/m2) are obtained, which indicates that the subsidence basin doesn’t reach the critical boundary, and this extraction of strip-partial UCG working face doesn’t form apparent subsidence basin and destroy the surface building in the observation period.

Key words: underground coal gasification (UCG), observation station, super-subcritical extraction, overlying strata movement, surface subsidence, measurement, geophysical prospecting