A Study of the Physical and Mechanical Properties of Yellow River Sediments and Their Impact on the Reclamation of Coal-Mined Subsided Land

Coal mining in China has resulted in numerous subsided areas, exacerbating land scarcity issues. The Yellow River carries a high sediment load of nearly 1.6 billion tons annually. Cleaning up the accumulated silt is costly and takes up land. Reusing the sediment from the Yellow River to fill and reclaim the subsided areas caused by coal mining addresses both sedimentation and land reclamation issues, killing two birds with one stone. Nonetheless, technical challenges have emerged, such as machinery sinking into the soil, difficulty draining water, and poor soil quality improvement. To tackle these issues, understanding the physical and mechanical properties of Yellow River sediment is essential. Results show that the average particle size (D50) is 0.08 mm, categorized as fine-grained sandy soil with a relatively uniform particle size distribution. The permeability coefficient is 2.91 × 10−3 cm·s−1, similar to that of silty soil, indicating the feasibility for filling reclamation. However, the low permeability requires drainage improvement to accelerate construction timelines. The internal friction angle of the sediment ranges from 34.67° to 31.76°, with a cohesion from 20.79 to 23.92 kPa. To ensure safe and stable construction, machinery must not sink into the fill material. It is recommended to enhance drainage to about 13% for quicker drainage and stable construction. The sediment has a compression coefficient of 0.05 MPa−1, indicating low compressibility. Mechanical compression is not economically viable during the reclamation process. Design elevation (H) and fill elevation (h) should account for cumulative deformation settlement.