Engineering Performance and Soil-Water Behavior of Tailings Sand Foundations in Arid Northwest China

Tailings sand primarily consists of fine sand, silt, and other non-cohesive soil particles. Due to its persistent saturation, it exhibits a high susceptibility to liquefaction under dynamic loading or fluctuating groundwater conditions, potentially leading to engineering failures such as foundation instability and slope failure. This study focuses on a representative tailings pond located in the northwest region of China. A series of geotechnical laboratory tests were conducted to investigate the fundamental physical and mechanical properties of tailings sand. The test results indicate that moisture content increases gradually with depth and stabilizes beyond a certain depth, while dry density decreases approximately linearly with increasing depth. Owing to the presence of certain metallic minerals, the specific gravity of tailings sand materials is slightly higher than that of conventional standard sand. Particle-size analysis reveals that the non-uniformity coefficient ranges from 2.04 to 3.1, and the coefficient of curvature varies between 0.72 and 0.97, indicating poor gradation. Compaction testing determined an optimum moisture content of 13.59%, corresponding to a maximum dry density of 1.868 g/cm3. Soil-water characteristic curve analysis shows that larger particle sizes are associated with enhanced drainage capacity and lower suction requirements. An increase in dry density significantly reduces the drainage rate but has a limited effect on the matric suction at the residual stage. This research provides valuable insights into the engineering behavior of tailings sand, supports the assessment of its performance in foundation applications, and offers practical guidance for the stabilization of and improvement in tailings sand foundations.