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<p>Failures of mine overburden (OB) dumps generate debris flows that differ from natural events due to the angular, poly-dispersed nature of blasted waste material, yet their mechanics remain poorly constrained. This study presents findings from 81 controlled flume experiments varying mass ratio (M<sub>R</sub>), size ratio (D<sub>R</sub>), and slope to quantify runout and flow dynamics. Three-way ANOVA (D<sub>R</sub> × M<sub>R</sub> × Slope) identifies M<sub>R</sub> as the dominant control, explaining 79.3% of variance in runout length (η² = 0.793, <i>p</i> &lt; 0.001). A key finding is an M<sub>R</sub>-dependent reversal in the D<sub>R</sub>-mobility relationship (η² = 0.045, <i>p</i> &lt; 0.001): at low fines content (M<sub>R</sub> = 0.1), increasing D<sub>R</sub> promotes coarse-particle interlocking and reduces runout. At higher M<sub>R</sub> (≥ 0.2), it enhances momentum transfer within a pore-pressure-sustained matrix, increasing runout. Saturated flows additionally exhibit slope-reversal behaviour at M<sub>R</sub> ≥ 0.2. Steeper slopes produce shorter runouts, contrary to dry granular flows, because higher shear rates accelerate pore-pressure dissipation and promote earlier friction-dominated arrest. Dimensionless analysis, the first such characterisation for mine OB dump debris, confirms collision-dominated flow throughout (Bagnold numbers 5,672 − 18,324; Savage numbers 0.94–6.92; supercritical Froude numbers 2.41–6.30). The friction number (622-2,776) reveals a spatially evolving stress state. The upstream friction-dominated flow transitions to downstream viscous-dominated flow, explaining deposits with a bouldery perimeter enclosing a liquefied core. These results provide composition-resolved guidance for hazard assessment. M<sub>R</sub> emerges as the primary field-characterisation parameter. The M<sub>R</sub>-conditioned D<sub>R</sub> sign reversal offers a validation benchmark for multi-phase debris-flow models. Deposit morphology identifies the governing flow regime.</p>

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Composition and slope controls on runout hazard in mine overburden dump debris flows: flume experiments and dimensionless flow regime analysis

  • 期刊论文

  • 发表日期：

    2026年6月16日

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  • Anup Tiwari,
  • Bibhuti Bhusan Mandal,
  • Monika Tewari

摘要

Failures of mine overburden (OB) dumps generate debris flows that differ from natural events due to the angular, poly-dispersed nature of blasted waste material, yet their mechanics remain poorly constrained. This study presents findings from 81 controlled flume experiments varying mass ratio (MR), size ratio (DR), and slope to quantify runout and flow dynamics. Three-way ANOVA (DR × MR × Slope) identifies MR as the dominant control, explaining 79.3% of variance in runout length (η² = 0.793, p < 0.001). A key finding is an MR-dependent reversal in the DR-mobility relationship (η² = 0.045, p < 0.001): at low fines content (MR = 0.1), increasing DR promotes coarse-particle interlocking and reduces runout. At higher MR (≥ 0.2), it enhances momentum transfer within a pore-pressure-sustained matrix, increasing runout. Saturated flows additionally exhibit slope-reversal behaviour at MR ≥ 0.2. Steeper slopes produce shorter runouts, contrary to dry granular flows, because higher shear rates accelerate pore-pressure dissipation and promote earlier friction-dominated arrest. Dimensionless analysis, the first such characterisation for mine OB dump debris, confirms collision-dominated flow throughout (Bagnold numbers 5,672 − 18,324; Savage numbers 0.94–6.92; supercritical Froude numbers 2.41–6.30). The friction number (622-2,776) reveals a spatially evolving stress state. The upstream friction-dominated flow transitions to downstream viscous-dominated flow, explaining deposits with a bouldery perimeter enclosing a liquefied core. These results provide composition-resolved guidance for hazard assessment. MR emerges as the primary field-characterisation parameter. The MR-conditioned DR sign reversal offers a validation benchmark for multi-phase debris-flow models. Deposit morphology identifies the governing flow regime.