Model tests on vacuum drainage consolidation of bauxite slime with high clay content

To address the technical challenge of low drainage-consolidation efficiency in bauxite residue with high clay content, the consolidation characteristics of two drainage configurations are systematically compared through vertical and horizontal drainage-consolidation model tests under graded vacuum loading. Combined with physico-mechanical tests, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) microstructural analyses, the response mechanisms between drainage interface efficiency and soil microstructure are elucidated. Under the staged vacuum loading, the horizontal drain configuration demonstrates 8.1% higher drainage volume and 17.7% shorter consolidation time compared to the conventional vertical drains. The horizontally drained soil exhibits superior uniformity, with smaller differential settlement and better load-bearing characteristics within the effective depth range. The post-consolidation measurements reveal the maximum variations of density and moisture content of 0.34 g/cm³ and 59.9% respectively in vertical drains, with the top layer penetration resistance being 8.7 times that of the bottom layer. In contrast, the horizontal drains show reduced variations of 0.16 g/cm³, 34.3%, and a 2.5-fold difference. The MIP and SEM analyses indicate that the vertically drained soil develops unimodal pore distribution dominated by micropores (< 0.1 μm), and the horizontally drained soil exhibits multimodal pore distribution including mesopores (1~100 μm). The study provides a novel approach for efficient dewatering of mineral slurries with high clay content, offering valuable engineering insights for the resource utilization of industrial solid wastes.