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| 基于悬移质、推移质和床沙交换的卵石夹沙河床粗化概率计算模型 |
| Probabilistic Model for Bed Material Coarsening in Gravel-Sand Riverbeds Based on Ternary Sediment Transport Transitions |
| 投稿时间：2025-05-21 修订日期：2025-08-26 |
| DOI： |
| 中文关键词: 河床粗化 泥沙交换 卵石夹沙河床 活动层沙量平衡 Markov转移概率矩阵 |
| 英文关键词: riverbed coarsening sediment exchange gravel-sand bed active layer mass balance Markov transition probability matrix |
| 基金项目:国家自然科学(U2040217,U2340223，52279079) |
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| 中文摘要: |
| 河流上修建水库后，坝下游往往发生持续冲刷导致河床显著粗化。常用的床沙粗化计算模型或方法多聚焦推移质与床沙或悬移质与床沙的单一交换过程，较少系统考虑床沙粗化过程中悬移质、推移质和床沙相互转化的物理机制。然而，山区河流的河床组成粒径范围宽，跨越多个数量级，不同粒径泥沙颗粒的动力学特性及运动状态差异大，不同运动形式的泥沙彼此之间转化频繁，有必要系统考虑床沙粗化过程中“悬移质-推移质-床沙”的交换机制，并构建相应的计算方法。基于泥沙运动统计理论，结合活动层沙量平衡原理与Markov泥沙转移概率矩阵，系统考虑床沙起悬、推移质落淤及悬移质落淤等泥沙冲淤交换过程及活动层厚度动态变化对床沙粗化进程的影响，建立了考虑“悬移质-推移质-床沙”交换机制的卵石夹沙河床粗化概率计算模型。通过汉江丹江口水库下游实测河床粗化资料和室内水槽试验数据对模型进行验证，结果表明模型能够准确预测粗化层级配及特征粒径变化，可动态反映水流冲刷与河床粗化的动态响应机制。通过实测与试验数据验证，表明在研究床沙粗化问题时，考虑床沙起悬和推移质、悬移质落淤过程是必要的，全面反映“悬移质-推移质-床沙”交换机制的河床粗化计算模型，物理机制更加完善，可显著提高卵石夹沙河床粗化的计算精度。 |
| 英文摘要: |
| Reservoir construction on rivers often triggers persistent downstream scouring, leading to pronounced bed material coarsening. Current coarsening models or methods primarily focus on single exchange processes—either between bed load and bed material or between suspended load and bed material—while offering limited treatment of the coupled transformation among suspended load, bed load, and bed material during coarsening. In mountainous riverbeds characterized by wide-graded sediments, grain sizes span several orders of magnitude. Sediment particles of different sizes exhibit significantly distinct hydrodynamic behaviors and transport modes. Transitions occur among these modes frequently, making it necessary to systematically account for the exchange mechanisms among“suspended load, bed load and bed material”during the bed coarsening process and to establish corresponding computational approaches. Building on sediment transport statistics, this study integrates the active-layer mass balance principle with a Markov sediment transfer probability matrix to systematically account for entrainment, deposition of bed load and suspended load, as well as the dynamic variation of active-layer thickness during bed evolution. On this basis, a probabilistic coarsening model has been developed for gravel-sand bed rivers that explicitly incorporates the “suspended load-bed load-bed material” exchange mechanism. The model is validated using both field measurements of bed coarsening downstream of the Danjiangkou Reservoir on the Han River and data from laboratory flume experiments. The results show that the model accurately predicts changes in grain-size distribution and characteristic particle sizes of armor layer, and effectively captures the coupled constraints between flow-induced scour and bed coarsening. Validation against field and experimental data further highlights the necessity of including entrainment and the deposition processes of both suspended and bed load in coarsening analyses. By fully representing the “suspended load-bed load-bed material” exchange mechanism, the proposed model offers a more complete physical description and significantly improves the predictive accuracy of coarsening in gravel-sand riverbeds. |
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