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<p>This study numerically investigates arsenic (As) transport in a homogeneous steady-state earth dam founded on an impermeable base using finite element modeling (SEEP/W and CTRAN/W, GeoStudio 2020). Locally sourced silty sand (SM) was characterized through laboratory tests, yielding a maximum dry density of 18.05 kN/m³, optimum moisture content of 13.1%, cohesion of 19&#xa0;kPa, friction angle of 33°, and hydraulic conductivity of 6.79 × 10⁻⁶ m/s. These parameters were used as model inputs for eight dam geometries with varying slopes (34°–59°), heights (15–20&#xa0;m), base widths (52–56&#xa0;m), and longitudinal slopes (0–2.28%), subjected to upstream As concentrations of 10–40&#xa0;mg/m³. Results show that As migration occurs primarily below the phreatic line, with negligible flux above it due to the assumption of saturated transport; unsaturated diffusion was intentionally excluded to isolate geometric effects. The solute flux increased from 3.86 × 10⁻¹² to 1.14 × 10⁻¹¹ kg/s·m² as concentration rose from 10 to 40&#xa0;mg/m³, while reducing dam height from 20&#xa0;m to 15&#xa0;m decreased flux by over 70%. Incorporating retardation (<i>R</i> = 12.6) and adsorption effects produced realistic attenuation consistent with the soil’s moderate permeability. The findings demonstrate that dam geometry exerts a stronger control on As transport than concentration magnitude. The novelty of this work lies in quantifying the combined influence of geometry, concentration, and hydraulic–sorption parameters on As migration, offering design-level insights for safer dam and embankment construction in arsenic-prone regions.</p>

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Numerical Modeling of Arsenic Transport in Homogeneous Earth Dams Under Varying Upstream Concentrations

  • 期刊论文

  • 发表日期：

    2025年12月29日

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  • Sushant Kumar,
  • Vijay Kaushik,
  • Geeta Devi,
  • Hazi Md. Azamathulla

摘要

This study numerically investigates arsenic (As) transport in a homogeneous steady-state earth dam founded on an impermeable base using finite element modeling (SEEP/W and CTRAN/W, GeoStudio 2020). Locally sourced silty sand (SM) was characterized through laboratory tests, yielding a maximum dry density of 18.05 kN/m³, optimum moisture content of 13.1%, cohesion of 19 kPa, friction angle of 33°, and hydraulic conductivity of 6.79 × 10⁻⁶ m/s. These parameters were used as model inputs for eight dam geometries with varying slopes (34°–59°), heights (15–20 m), base widths (52–56 m), and longitudinal slopes (0–2.28%), subjected to upstream As concentrations of 10–40 mg/m³. Results show that As migration occurs primarily below the phreatic line, with negligible flux above it due to the assumption of saturated transport; unsaturated diffusion was intentionally excluded to isolate geometric effects. The solute flux increased from 3.86 × 10⁻¹² to 1.14 × 10⁻¹¹ kg/s·m² as concentration rose from 10 to 40 mg/m³, while reducing dam height from 20 m to 15 m decreased flux by over 70%. Incorporating retardation (R = 12.6) and adsorption effects produced realistic attenuation consistent with the soil’s moderate permeability. The findings demonstrate that dam geometry exerts a stronger control on As transport than concentration magnitude. The novelty of this work lies in quantifying the combined influence of geometry, concentration, and hydraulic–sorption parameters on As migration, offering design-level insights for safer dam and embankment construction in arsenic-prone regions.