Study on the spatial distribution regularities of coal gangue accumulation in the coal mining area of northern Germany—taking coal gangue accumulation area of Ibbenbueren for instance

Ibbenbueren is one of the mining areas for anthracite coal, which is located in the north of Nordrhein-Westfalen, Germany (Fig. 1). The field investigation showed that: 1, an old coal gangue heaps Ibbenbueren Althalde (IA followed) in this area has a accumulation period of more than 10 years, which are mainly composed of coal gangue with rich pyrite as well as massive sulphide (Liang Liuke et al. 2002). 2, new coal gangue accumulation Ibbenbueren Halde (IH followed) has a short stacked year, which has the component of fresh coal gangue. 3, the soil in Ibbenbueren Spuelfeld (IS followed) is formed by coal mining waste sludge producing in coal washing process.