Distribution and Stability of Soil Aggregates over the Fissure Zones in Reclaimed Coal Mining Waste Dumpsite

【Objective】 Restoring coal mining waste dumps is a way to alleviate their detrimental impact on environment. In this paper, we present the results of an experimental study on distribution and stability of soil aggregates in a reclaimed coal mining overburden dump. 【Method】 The experiment was carried out at a reclaimed coal mine dump site in a grassland region in northern China. We measured the development of fissures from Zone I (GF) to Zone three (GFIII) in the fissure zone. The composition and distribution soil aggregates in these zones were determined using dry-wet sieve method. Aggregate stability and its relationship with the fissures was analyzed. 【Result】 The content of the >0.25 mm air-dried aggregates over the fissure zones was 23.02%~42.70%, and content of the >0.25 mm water-stable soil aggregates was 16.9%~29.52%. There was no significant difference between air-dried aggregates and water-stable aggregates. The content of the >0.25 mm water-stable soil aggregates in the 0~60 cm soil layer in GF, GFⅡ and GF Ⅲ was 25.26%, 26.57%, 23.62%, respectively, while the percentage of aggregate destruction in the three fissure zones was 20.77%~36.17%, 20.52%~25.00%, and 26.58%~40.56%, respectively. The percentage of aggregate destruction in 0~10, 10~20, 20~30, 30~40, 40~50, and 50~60 cm soil layers was 28.81%, 29.96%, 26.19%, 23.50%, 24.91%, and 29.38%, respectively. The fractal dimension of air-dried and water-stable soil aggregates was 2.847~2.919 and 2.898~2.942, respectively. Small aggregates and fine particles are the dominant aggregates. The mean mass diameter (MWD) and geometric mean diameter (GMD) of the air-dried aggregates in three fissure zones were 1.11, 1.05, 1.28 mm, and 0.45, 0.44, 0.49 mm, respectively. The MWD and GMD of water-stable soil aggregates in the three fissure zones were 0.67, 0.73, 0.72 mm, and 0.36, 0.38, 0.37 mm, respectively. Soil in GFⅡ had good structure and aggregate stability. Most of water-stable soil aggregates in the fissure zones were unstable due to the formation and development of fissures. 【Conclusion】 The formation and development of fissures in the reclaimed coal mining overburden dump reduced the stability of soil aggregates, thereby resulting in aggregate segmentation. The larger and wider the fissures were, the less stable the soil aggregates were.