Various phases in surface movements linked to deep coal longwall mining: from start-up till the period after closure

Abstract

AbstractThis paper covers the entire lifetime of an underground coal mine, including the start-up of the mining operations and the period after the closure and sealing of the underground workings. Measurements of the vertical surface movement are presented for three neighbouring mines in the Belgian Campine coal basin, where the longwall mining method was applied. First, the monitoring of the initial phase showed that the impact of the first panel was smaller than the impacts of the following two neighbouring panels. When the second panel was mined, a change in the induced surface tilt was observed in the immediate proximity of the panels. Second, data for a transect with a length of about 2.5 km were presented, covering a total time of 54 years, of which the first 31 years were during the active life of the mine. Average subsidence rates of up to − 0.3 m/year were observed. After the mine was closed and the pumping facilities were stopped, the average uplift rate was situated mostly between 4 and 16 mm/year, but a value of 141 mm/year also was measured. Thirty years after closure, the upward movements are still occurring. Third, the phase of uplift is analyzed in more detail over a full north–south transect. A clear narrow maximum was observed for the uplift, corresponding to a total vertical movement of 0.2 m over approximately an 18-year period. All these phases are relevant, for example when analysing damage to buildings and infrastructure. Damage becomes visible when the cumulative movement and loading exceed critical limits and not necessarily when the largest rate of movement is observed, for example.