Impact on soil physical qualities by the subsidence of coal mining: a case study in Western China

It is of great importance to investigate the effect of soil physical quality index on the surface soil by the subsidence induced by coal mining to quantify the impact of land surface change on soil physical quality. In this paper, sampling locations were distributed according to the theory of mining subsidence. The soil samplings were obtained in the same location before and after mining, and the in-door experiments of seven soil physical quality index were conducted. It was proved that coal mining could reduce the average value of soil water content, cohesion and organic matter, and increase the average value of internal fraction angle, while in comparison, it did not influence soil bulk density, dry density and porisity very much. The relationship among soil physical quality index was also influenced by the subsidence induced by coal mining influences. Although the statistical analysis showed that the average values of soil water content, organic matter and cohesion were greatly affected by subsidence of coal mining, the same phenomenon may not always happen in every sampling location due to soil spatial and temporal variability. The theory of cumulative probability was proved to be suitable for describing the impact on soil physical qualities by the subsidence of coal mining before and after mining. The subsidence increased the cumulative probability to get the same value of soil water content, cohesion and organic matter, while it was decreased to get the same value of internal fraction angle.