Research on the Relationship between Grain Composition and Repose Angle of Coal Gangue in Dongkuang Mine, Heshan City, Guangxi, China

Heshan, a city in Southwest China, has been built over an old coal mining area. Due to low level of reclamation, coal gangue had been stacked in large heaps and caused geological environmental problems. To facilitate designing management project of coal gangue, we made an investigation of the largest coal gangue heap in Dongkuang Mine of Heshan. Firstly, the grain composition of coal gangue was estimated through the sieving method, then the representative grading curve was drawn through the statistics method of coarse grain content, and lastly the relationship between the repose angle and grain grading was studied by piling up coal gangue with different mix proportion. The result indicates that there is a wider range of grain size in the upper part of coal gangue heap, and the representative grain grading is well graded and easy to be compacted as filling materials. Besides, the wavy relationship curve of repose angle and coarse grain content shows that the content of 70% is the inflection point of ascent stage and 85% the inflection point of descent stage of the repose angle. What's more, the repose angle corresponding to the representative grading of coal gangue is approximately 38.4 degrees and this has guiding significance for management project of coal gangue.