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首页> 外文期刊>Estuarine Coastal and Shelf Science >Quasi-hydrodynamic lubrication effect of clay particles on sand grain erosion
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Quasi-hydrodynamic lubrication effect of clay particles on sand grain erosion

机译：粘土颗粒对砂粒侵蚀的拟流体动力润滑作用

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摘要

Minor changes in the mass physical properties of submerged sand beds can have significant consequences relative to bed stability against erosion. To examine the effect of small amounts of clay-sized particles in bed pore water on the critical shear stress τ_c for the erosion of sand grains, flume experiments were carried out on the erosion of quartz sand beds impregnated with clay particles. Starting with no clay, as the clay mass fraction ψ was increased, τ_c was found to decrease below the value for pure sand τ_(co) at ψ = ψ_m, then reverted to τ_(co) at ψ =ψ_r and continued to increase above τ_(co) as ψ was increased further. Post-experimental analysis suggests that ψ_r is the pore space-filling fine sediment fraction above which sand erosion is significantly influenced by clay. In the range of ψ ≥ ψ_m, slider-bearing type lubrication due to the viscosity of the clay-laden interstitial fluid appears to govern the dependence of τ_c on ψ, mimicking Petroff's law of thick-film lubrication. When ψ< ψ_m as ψ decreases lubrication is increasingly curtailed by grain asperities, and τ_c reverts ultimately to τ_(co) at ψ = 0. An equation relating τ_c to ψ is proposed in analogy with the quasi-hydrodynamic Stribeck function for lubrication. The observed effect of clay particles appears to be significant enough to require its consideration in coastal and estuarine sediment transport modeling. It may also be a factor in the estimation of bed stability when biological activity in the benthic boundary layer introduces fine particles in clean sand beds.
机译：相对于抗侵蚀的床层稳定性，淹没的沙床的质量物理特性的微小变化可能会产生重大后果。为了检查床孔隙水中少量粘土大小的颗粒对临界剪切应力τ_c对砂粒侵蚀的影响，对含粘土颗粒的石英砂床的侵蚀进行了水槽实验。从无粘土开始，随着粘土质量分数ψ的增加，发现τ_c在ψ=ψ_m时降至纯砂τ_（co）的值以下，然后在ψ=ψ_r时恢复为τ_（co）并继续增加至τ_（co）随着ψ进一步增加。实验后分析表明，ψ_r是填充孔隙的细小沉积物部分，在该部分之上，砂土侵蚀受到黏土的显着影响。在ψ≥ψ_m的范围内，由于载有粘土的间隙流体的粘度而导致的滑动轴承式润滑似乎控制了τ_c对ψ的依赖性，从而模仿了厚膜润滑的彼得罗夫定律。当ψ<ψ_m随ψ减小而减小时，晶粒粗糙度逐渐减少润滑，并且τ_c最终在ψ= 0时恢复为τ_（co）。与准流体力学Stribeck函数类似，提出了将τ_c与ψ相关的方程式。所观察到的粘土颗粒效应似乎足够重要，需要在沿海和河口沉积物运输模型中加以考虑。当底栖边界层中的生物活性在干净的沙床中引入细颗粒时，这也可能是估算河床稳定性的一个因素。

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