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Mirosław CHUDEK, Piotr STRZAŁKOWSKI, Roman ŚCIGAŁA

The duration of mining land shifts evidenced by geodetic survey

This paper contemplates the determination of the duration of the final depression stage of mining land. The final depression stage duration is the time difference between (1) the end of mining at a given geographical point (or removal of the mining face from that point to a distance exceeding the mining impact range) and (2) the actual cessation of the depression forming process at that point. The paper characterizes a surface depression forming process, caused by underground mining, as evidenced by field geodetic survey at one of the mining facilities operated by Jastrzębska Spółka Węglowa and identifies the individual stages of that process. To determine the contemplated duration with varying mining and geological conditions it was assumed that the significant factors contributing to the duration of mining effects on land shifting include: mining depth, mining front advance rate, depleted bed portion shutdown method, and the rock mass characteristics within the contemplated mining operation. The paper focuses on a single case of a specific mining land in the vicinity of a specific mine, where the majority of the listed contributing factors exhibited great similarity. In order to obtain the simplest empirical relationship, it was assumed that the mining depth is the most critical factor at the showcased mine which determines the duration of mining land shifts. The analyses of available field survey measurements results enabled selecting 7 cases of mining land shift cessation within a field mined between ca. 600 m and ca. 725 m of depth below the terrain level. Based on the established durations of these shifts, a regressive linear relation was determined and expressed with the formula (3). The formula outputs an approximate final stage duration of rock mass shifts. The formula can be applied to mining conditions in the areas where there are no survey measurement results available for an explicit determination of the actual cessation of mining land shifts.