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<p>Post-event debris-flow gullies frequently retain substantial loose material, yet the residual risk they pose is difficult to evaluate due to a scale mismatch: catchment-scale runout models lack the resolution to assess local structural impacts, while structural-scale models typically rely on idealized inflow conditions. To address this, we develop a cross-scale analytical framework applied to Baima Gully along the Jiumian Expressway, which retained abundant loose debris following the 16 August 2020 event. Residual source materials were quantified through field investigations, UAV surveys, high-resolution topographic data, and remote-sensing interpretation. The 2020 event was back-analyzed using MassFlow software to calibrate dynamic parameters, and the validated model was then employed to predict potential residual debris-flow behavior. Resulting hydrographs at the dam site were subsequently used as inputs for fluid–structure interaction simulations in ANSYS CFX and complementary physical flume tests. MassFlow predictions indicate that a future residual flow could attain a peak velocity of 4.11 m·s<sup>−1</sup> near the gully outlet and form a fan-shaped deposit with a maximum flow depth of approximately 5.91 m. Implementation of a proposed solid gravity check dam reduces outlet impact velocity by 49%, decreases inundation area by 41%, and attenuates peak discharge through the spillway by 63.5%. Simulations and flume experiments consistently show that the dam promotes an upstream wedge-shaped deposit, redirects subsequent surge waves, and shifts the peak pressure zone from the dam toe to its mid-height region. Flume measurements reveal a reduction in peak impact pressure from 42.85 kPa to 15.96 kPa, reflecting a buffering mechanism involving flow redirection, frictional dissipation, and soil arching. Structural verification yields a safety factor of 1.62 for the C25 concrete dam. The proposed framework effectively integrates residual risk prediction, mitigation performance evaluation, and structural response analysis, offering a robust basis for check-dam design in post-event debris-flow gullies along mountainous transport corridors.</p>

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Dynamic characteristics of residual debris flows and response mechanisms of check dam in Baima Gully along the Jiumian Expressway

  • 期刊论文

  • 发表日期：

    2026年7月29日

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  • Enxi Qiu,
  • Wenhao Liu,
  • Yunbao Yue,
  • Chuanbao Li,
  • Wengang Xu,
  • Yuwei Li,
  • Jun Liu

摘要

Post-event debris-flow gullies frequently retain substantial loose material, yet the residual risk they pose is difficult to evaluate due to a scale mismatch: catchment-scale runout models lack the resolution to assess local structural impacts, while structural-scale models typically rely on idealized inflow conditions. To address this, we develop a cross-scale analytical framework applied to Baima Gully along the Jiumian Expressway, which retained abundant loose debris following the 16 August 2020 event. Residual source materials were quantified through field investigations, UAV surveys, high-resolution topographic data, and remote-sensing interpretation. The 2020 event was back-analyzed using MassFlow software to calibrate dynamic parameters, and the validated model was then employed to predict potential residual debris-flow behavior. Resulting hydrographs at the dam site were subsequently used as inputs for fluid–structure interaction simulations in ANSYS CFX and complementary physical flume tests. MassFlow predictions indicate that a future residual flow could attain a peak velocity of 4.11 m·s−1 near the gully outlet and form a fan-shaped deposit with a maximum flow depth of approximately 5.91 m. Implementation of a proposed solid gravity check dam reduces outlet impact velocity by 49%, decreases inundation area by 41%, and attenuates peak discharge through the spillway by 63.5%. Simulations and flume experiments consistently show that the dam promotes an upstream wedge-shaped deposit, redirects subsequent surge waves, and shifts the peak pressure zone from the dam toe to its mid-height region. Flume measurements reveal a reduction in peak impact pressure from 42.85 kPa to 15.96 kPa, reflecting a buffering mechanism involving flow redirection, frictional dissipation, and soil arching. Structural verification yields a safety factor of 1.62 for the C25 concrete dam. The proposed framework effectively integrates residual risk prediction, mitigation performance evaluation, and structural response analysis, offering a robust basis for check-dam design in post-event debris-flow gullies along mountainous transport corridors.