Anna Oliskiewicz-Krzywicka, Piotr Stachowski
Uniwersytet Przyrodniczy, Poznań

The work presents a detailed analysis of landscape changes in 8 test areas constituting part of the internal dump of the “Kazimierz Północ” of the “Konin” open-pit brown coal mine with the top part of the land at the level of the adjacent areas. After technical rehabilitation performed by the Mine and completed in 1998, which involved, among others, leveling the landscape of the devastated area, regulation of the hydrographic conditions by building the necessary drains, the purchaser of the post-mining area performed rehabilitation and agricultural land planning. Landscape measurements involving determination of the elevation of selected points were performed in three sessions: in 2000 during agricultural rehabilitation, after the rehabilitation was completed (2005) and during agricultural land planning (2010). During all of those three time periods, leveling was performed with reference to the existing vertical control of the landscape. Land measurements and calculations were performed in accordance with the recommendations provided in the technical instructions G-4 “Topographic surveys” and G-4.3 “Direct elevation surveys”, which were valid at the time when the measurements were performed. The WinKalk program was used for the purpose of calculating the elevation of the points as well as for determining their x,y coordinates. On the basis of the results, the area contour lines were generated for every measurement session in the MicroMap program. The coordinates of the points were then imported (with the use of the C-Geo program) into the ArcGis program as shape files. On their basis, numeric terrain models were generated for every measurement session. The TIN model as the best one for engineering applications was selected as the interpolation method. For the purpose of quantitative specification of land subsidence irregularities, terrain surface areas on particular elevation levels (with the interval of 0,25 m) were calculated on individual elevation models. Next, average subsidence values generated on the subsidence map between particular pickets in every one of the test areas were calculated for every one of the 8 test areas. The results of the analyses confirmed that the analyzed post-mining area subsided in an irregular, uneven manner. Subsidence was significant in one of the areas and slight in a different, adjacent area. As a result, irregularities formed in the dump area – depressions separated with high grounds. In the period between 2000 and 2005, the average variation of elevation changes reached up to 0,56 m, and for the following period (2005–2010) variations were greater and reached up to 0,7 m. The subsidence map of the post-mining area generated for the digital elevation model showed that the average subsidence values calculated for the micro-landscape of the dump are within the standard tolerance (Pr-PN-G-07800) of optimal subsidence (up to 3%), assumed for agricultural management dumps. This resulted from the dump leveling works conducted by the land owner over the first years of their agricultural activity. On the basis of the subsidence map prepared, areas with subsidence values higher than the values assumed in the standard were determined (2002) from 2,4% (in 2000) to 7,2% (in 2010) in relation to the whole small dump land area (2,24 ha). The dump soil subsidence results are of great significance while designing the target elevation of different types of dumps as well as for balancing the available dump soil volume in relation to the volume required. The phenomenon of irregular land subsidence of post-mining areas presented in the work as well as its scale practically eliminates the possibility of conducting agricultural activity without ongoing land leveling by the user, in particular during the first years after dump soil deposition.

Słowa kluczowe
górnictwo odkrywkowe, zwałowiska pogórnicze, osiadanie gruntu zwałowego

Landscape Change in a Post-mining Area

Key words
opencast mining, post mining dumping, settlement of dump soil

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