Uplift of the surface of the earth above abandoned coal mines. Part A: Analysis of satellite data related to the movement of the surface

After the closure of several coal fields in Europe at the end of the 20th century, a new phenomenon in the field of strata or ground control was observed above abandoned coal mines, i.e., the upward movement or uplift of the surface. This also was observed above the Eisden mine in the eastern part of the Belgian Campine coal basin. The uplift was measured above the area mined by the longwall method and its surroundings, and it is linked to the flooding of the underground infrastructure and the surrounding rock mass. A detailed analysis of Interferometry with Synthetic Aperture Radar data showed the complexity of this phenomenon. There was a large spatial variation of uplift values, but there also was a variation as a function of time. At the start of the observation (about four years after the mine was closed), the average uplift rates were characterized by a wide spread of values, e.g., in a sub-area of 1 km(2). Afterwards, the range of the values narrowed somewhat, and the rate of uplift decreased during the 20-year period of the study. For the central area, the uplift averaged about 22 mm/year during the first half of the observation time, and it averaged about 10 mm/year for the second half. Along a north-south transect, the shape of the curve of the uplift values could be best approximated by an inverse trough. However, the curve was not fully symmetrical. The extent of the zone of influence was several times larger than the depth of the longwall panels.

Automated summary

After the closure of several coal fields in Europe, a new phenomenon of surface uplift above abandoned coal mines was observed, potentially linked to underground flooding. The values of uplift varied spatially and over time, with a gradual decrease in uplift rate observed over a 20-year period.